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Wants to Stall on Cold Start by Ry86GT
Started on: 08-23-2013 10:10 AM
Replies: 27 (2161 views)
Last post by: seq on 05-22-2014 09:26 PM
Ry86GT
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Report this Post08-23-2013 10:10 AM Click Here to See the Profile for Ry86GTSend a Private Message to Ry86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Need some advice from the experts on where to start (well... continue) trouble shooting here.

This ONLY happens on cold starts: those being where the car has at least sat over night or for more than a few hours after a drive. Once the car has warmed up it idles and drives beautifully and you can start it and stop it at your hearts desire just fine. You can go a couple of hours without it behaving weird on re-start.

My car is not a DD so it may get driven a couple of times a week in good weather. Usually it is stopped and started at least a couple of times on those outings.

My first time starting the car after it has been sitting the same thing always happens. The car will start right up - like immediately, no hesitation there. Revs to about 1,500rpm then it wants to try and die a few times, it tries to stall out. The revs drop to 600 ish rpm and if I'm lucky it will bounce itself back but lately I've been having to tap the throttle to keep it alive. After doing this 2-3 times it generally idles fine until it warms up.

It runs a little different until it hits that certain point where you can tell it's warmed up - it just sounds like a switch was flicked and its running properly. The idle smooths out just a little bit, just enough to change it's tone a little. This usually happens about a minute or so after starting. If I try to drive it too soon after starting it as soon as I let the clutch out and put a load on the engine it wants to die. I have to clutch in to keep it alive. Once it hits that point where it's warmed up and running ok this is not and issue and I can drive / creep with the clutch like normal. Idle is also rock steady after that point, it will go from 1400rpm to 1000/950 ish rpm as it continues to warm up.

Things I've done as of the beginning of this season:
- Full tune up: plugs/wires/cap/rotor/coil
- O2 sensor, had failed and caused a lean code (which made it run rich)
- almunium vac lines
- fuel filter changed
- IAC removed and cleaned, retracted, re-installed and ECM reset
- New IAT sensor
- corrected a mis-adjusted throttle body stop screw. Previous owner had it way open - was getting a high idle code. I now believe they did that to try and tune out this cold start issue.
- re-set the timing (set it 2 degrees advanced)
- I have added a large ground from the bolt under the EGR solenoid to the negative battery terminal. I have more 8awg wire and connectors to go from the same spot on the block to the chassis, and a couple of others in different locations. I plan to add 2-3 more good solid grounds.

I checked the fuel pressure and in my opinion it was borderline low, but the car is running fine (once warmed up...) and my experienced mechanic neighbour said it was ok and that the regulator was working. However I did notice that the fuel pressure drops pretty quickly after shut off.

The only other issues that I know of in the car are that the a/c doesn't do a damn thing and i have a valve seal on it's way out. I will get a puff of smoke if I've driven for a while, let the car site for an hour or two and re-start. I currently have no codes.

I've been trying to do some reading and some searching and seem to see two possibilites: MAP and coolant temp sensor. Which is more likely? Can anyone point me where to start trouble shooting further? I don't want to just throw money at the car in the form of parts I don't need. Any help would be greatly appreciated.
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hiwil88formula
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Report this Post08-23-2013 10:32 AM Click Here to See the Profile for hiwil88formulaClick Here to Email hiwil88formulaSend a Private Message to hiwil88formulaEdit/Delete MessageReply w/QuoteDirect Link to This Post
It looks like you are on the right track. One thing that stood out to me is your timing. On the 2.8 is should be 10 degrees advance timing. This. Might be the main culprit to your issue. Just a thought.
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Ry86GT
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Report this Post08-23-2013 10:47 AM Click Here to See the Profile for Ry86GTSend a Private Message to Ry86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
I will re-time to stock 10 degrees. I had it there, it just felt a little punchier at 12. I don't want that if it causes issues though.

If you can believe it or not previous owner had it advanced way off the charts. I backed it down. All of the previous work was to sort out a driveability issue. Now that's been well sorted out and this (and air getting into the clutch lines) is the only problem I have left at the moment.

I know how to fix the clutch lines, Rodney master and slave, for now I'm ok with bleeding it once a month or so. I'd like to get this starting issue sorted. Rodney clutch parts will be on my xmas list.
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hiwil88formula
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Report this Post08-23-2013 10:51 AM Click Here to See the Profile for hiwil88formulaClick Here to Email hiwil88formulaSend a Private Message to hiwil88formulaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Make sure you put it in diagnostic mode first before you time it.
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Report this Post08-23-2013 01:26 PM Click Here to See the Profile for 92wastheyearClick Here to Email 92wastheyearSend a Private Message to 92wastheyearEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Ry86GT:
I've been trying to do some reading and some searching and seem to see two possibilites: MAP and coolant temp sensor. Which is more likely? Can anyone point me where to start trouble shooting further? I don't want to just throw money at the car in the form of parts I don't need. Any help would be greatly appreciated.


I had this exact issue with my 87 GT when I first acquired it....I mean the exact symptoms. What I did that cured the issue was changed the IAT Temp Sensor (which I think yo already swapped if I read correctly) and the Coolant Temp Sensor (for ECM). I would try swapping out the CTS after you check the timing. Mine now starts easy and runs great even cold

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Report this Post08-23-2013 01:38 PM Click Here to See the Profile for PyrthianClick Here to Email PyrthianSend a Private Message to PyrthianEdit/Delete MessageReply w/QuoteDirect Link to This Post
almost all "cold run" symptoms come from 2 places: the CTS (coolant temp sensor) & IAT (intake air temp) sensors.
the CTS is on the intake manifold, at the front of the engine, sticking out towards the pulleys, and the IAT is in the air filter can.
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Report this Post08-23-2013 01:49 PM Click Here to See the Profile for 92wastheyearClick Here to Email 92wastheyearSend a Private Message to 92wastheyearEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Pyrthian:

almost all "cold run" symptoms come from 2 places: the CTS (coolant temp sensor) & IAT (intake air temp) sensors.
the CTS is on the intake manifold, at the front of the engine, sticking out towards the pulleys, and the IAT is in the air filter can.


Thanks again for that advice (Pyrthian gave me this same advise when I was having this problem)

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Report this Post08-23-2013 01:56 PM Click Here to See the Profile for Ry86GTSend a Private Message to Ry86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks guys. That's what my gut was telling me but I wanted to check first.

Oddly enough my local parts store has a CTS on his shelf for $28. Not a bad part price for being in Canada... I'm going to pick it up tonight and swap it in this weekend. That works out well because I can add the other ground cables that I wanted to add at the same time.

I did change the IAT sensor already. My car came with an aftermarket intake and I refurbished the original and reinstalled it. I didn't like the filter being in the fender and the original sensor was pretty corroded looking. The car now has the stock intake with a new IAT sensor already. It wa sa cheap one that I tacked onto one of my first Rock-auto orders so I threw it in.

I know where the CTS is, I saw it when adding my ground cable. I forgot to mention that I had already tried cleaning the contacts on the connector and sensor and it made no difference. Do I lose a ton of coolant when swapping the sensor out? It's below the thermostat and I have a bit of coolant left over from when I did the heater core, but it's certainly not a full jug. Just wondering if I need to buy more or not.
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Report this Post08-23-2013 02:06 PM Click Here to See the Profile for 92wastheyearClick Here to Email 92wastheyearSend a Private Message to 92wastheyearEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Ry86GT:

. Do I lose a ton of coolant when swapping the sensor out? It's below the thermostat and I have a bit of coolant left over from when I did the heater core, but it's certainly not a full jug. Just wondering if I need to buy more or not.


No...not much at all ...just what is in the thermostat tube and a little more. a quart maybe if that much. One thing .....most of these cars have an "adaptor" or something on the CTS. When I pulled mine out I thought I was in trouble because the base wasn't the same size as the replacement sensor....I looked closer and it was seperate peice ....just spin it off the old sensor and use it again. Avoid teflon tape


Oh...something else ...you will have to loosen the part right above the sensor to get a wrench or deep socket (I used a spark plug socket) on the sensor

[This message has been edited by 92wastheyear (edited 08-23-2013).]

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Report this Post08-23-2013 02:36 PM Click Here to See the Profile for PyrthianClick Here to Email PyrthianSend a Private Message to PyrthianEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Ry86GT:
Thanks guys. That's what my gut was telling me but I wanted to check first.

Oddly enough my local parts store has a CTS on his shelf for $28. Not a bad part price for being in Canada... I'm going to pick it up tonight and swap it in this weekend. That works out well because I can add the other ground cables that I wanted to add at the same time.

I did change the IAT sensor already. My car came with an aftermarket intake and I refurbished the original and reinstalled it. I didn't like the filter being in the fender and the original sensor was pretty corroded looking. The car now has the stock intake with a new IAT sensor already. It wa sa cheap one that I tacked onto one of my first Rock-auto orders so I threw it in.

I know where the CTS is, I saw it when adding my ground cable. I forgot to mention that I had already tried cleaning the contacts on the connector and sensor and it made no difference. Do I lose a ton of coolant when swapping the sensor out? It's below the thermostat and I have a bit of coolant left over from when I did the heater core, but it's certainly not a full jug. Just wondering if I need to buy more or not.


yes, it will dump around a quart of coolant.
also, newer CTSs have a different connector - you will likely need to splice it in.
it just changed to a weather-pack type connector - the sensor is the same (or better)
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Report this Post08-23-2013 06:12 PM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have the same cold start symptom as well... stalls once nearly every time when the RPMs spool down from initial start up, and doesn't like to have a load put on it until after 2 or 3 minutes of idling. My CTS packed it in about two weeks ago and I figured replacing it might solve the problem but it didn't. I haven't replaced the IAT yet but that's the next step. It's an annoying problem.
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Report this Post08-24-2013 12:44 PM Click Here to See the Profile for tonycampbell86gtClick Here to visit tonycampbell86gt's HomePageClick Here to Email tonycampbell86gtSend a Private Message to tonycampbell86gtEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have the same issue. I replaced the IAT and CTS, didn't help. I replaced the MAP, and it acted a little better, thought it took care of it, but still dies after the rpms slow down, just like what you are describing. Once it warms up, it seems to be fine. Any thoughts as to what might be causing this?

Tony
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Report this Post08-26-2013 08:53 AM Click Here to See the Profile for Ry86GTSend a Private Message to Ry86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well I got the CTS in on Saturday. Also added a few more grounds like I wanted to.

Initial startup after swapping it was good, no wanting to stall - however I had unplugged the battery and the ECM was re-setting the IAC at the time. That was a cold start, and the car did drive fine.

On Sunday we went for another drive. First start-up was terrible. Back to the same old thing, except it wanted to stall more than a few times. I probably had to tap the throttle about 6 times to keep it alive. Then it caught and I was good to go. Cold performance after it caught on seemed marginally better, once it caught on it wasn't really trying to stall with a load put on it.

It's one of two things - it's either not getting air or not getting fuel. Spark is obviously good, short of the distributor itself I've re-done the entire ignition system. It starts up nearly instantly and when it tries to stall comes back to life the instant I touch the throttle.

Arrrg it's annoying.
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Report this Post08-26-2013 01:08 PM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm starting to think it may be related to the cold start injection system, and if it is, it's most likely the CSI temperature sensor.



It seems as though most of the other coolant temperature senders are reaching the end of their useful lives at this stage so it's quite possible that the CSI thermocouples are finally crapping out too. The system is supposed to dump extra fuel into the manifold while cranking and can stay on for varying lengths of time depending on the temperature of the coolant. If it starts misbehaving, then there's a good chance we'd get the symptoms we're getting. I wonder if they're still available.
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Report this Post08-26-2013 02:02 PM Click Here to See the Profile for 92wastheyearClick Here to Email 92wastheyearSend a Private Message to 92wastheyearEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Bloozberry:

I'm starting to think it may be related to the cold start injection system, and if it is, it's most likely the CSI temperature sensor.



It seems as though most of the other coolant temperature senders are reaching the end of their useful lives at this stage so it's quite possible that the CSI thermocouples are finally crapping out too. The system is supposed to dump extra fuel into the manifold while cranking and can stay on for varying lengths of time depending on the temperature of the coolant. If it starts misbehaving, then there's a good chance we'd get the symptoms we're getting. I wonder if they're still available.


This looks like it might be it



If so, it is a spendy little gadget at nearly $150 from RockAuto
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Report this Post08-26-2013 04:02 PM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well then... that explains why nobody's bought one just for the heck of it and tried it out. That's crazy expensive! I have a couple spare engines that I might try swapping the sender out with to see if it makes a difference.
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Report this Post08-26-2013 04:23 PM Click Here to See the Profile for Ry86GTSend a Private Message to Ry86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
I thought that the CSI got its power from the starter's power circuit, and thus was only on so long as the starter was being engaged?

My issue is not starting, it starts almost right away.

It's that it wants to stall for a few seconds immediately after it's been cold started.

[This message has been edited by Ry86GT (edited 08-26-2013).]

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Report this Post08-26-2013 06:06 PM Click Here to See the Profile for 92wastheyearClick Here to Email 92wastheyearSend a Private Message to 92wastheyearEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Ry86GT:

I thought that the CSI got its power from the starter's power circuit, and thus was only on so long as the starter was being engaged?

My issue is not starting, it starts almost right away.

It's that it wants to stall for a few seconds immediately after it's been cold started.


That is a good point. The CSI should not have an impact after the car is started ....not like the CTS AND IAT sensor
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Report this Post08-26-2013 06:14 PM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Ry86GT:
I thought that the CSI got its power from the starter's power circuit, and thus was only on so long as the starter was being engaged?


That is correct, but if the CSI isn't turning on at all, then you (we) could possibly be suffering from the effects of not enough fuel. Remember, the CSI just dumps a heap of raw fuel into the intake manifold (not much different than pouring a 1/4 cup of fuel into an old carburettor) to keep the engine running past initial light off.

 
quote
Originally posted by Ry86GT:
My issue is not starting, it starts almost right away. It's that it wants to stall for a few seconds immediately after it's been cold started.


I know. Many of us have the exact same problem... it's been discussed several times before and no one has come up with a solution yet. To my knowledge though, no one has checked the CSI system for proper functioning so this is an educated guess... not a sure-fire solution. But the number of possibilities is quickly dwindling: so far we know it's not the IAT, nor the CTS, nor a combination of both.

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Report this Post08-26-2013 08:02 PM Click Here to See the Profile for fierogt28Click Here to Email fierogt28Send a Private Message to fierogt28Edit/Delete MessageReply w/QuoteDirect Link to This Post
Guys, remember this is a fiero here, its over 25 years old and has the technology from the 80s.

I have a way of driving my fieros and always warm them up before hitting the road.

My 88s are well treated. Don't just start the engine and take off 1-2 minutes later. I always warm them up for 6-7 min.
Then before I leave, I wait for the RPM to drop at 1100, or 1000. When started they always idle at 1600-1700RPMs on cold
starts. Also remember that most people here may not of replaced most sensors, or could be still original.
One thing is, if you replace your sensors, replace them with quality sensors, not e-bay junk or used senors.
Buy them from a good known automotive parts store. Don't buy cheap parts, you'll get crappy results. Realistically when an engine
is out for overhaul, replace all the sensors. Its the time to do it...your there.

I keep telling people to stop buying parts off of e-bay, you have no service after buy from that site. Plus they think they are getting a deal
and get crap. If you buy, you have to know what you are getting. Just because the price is good, doesn't mean the parts are good.

" True Example..."

2-3 years ago, some forum member posted that he wanted to buy used ball-joints and tie-rods for his 86SE.
He bought them because he was too cheap to buy new ones. Like I mean, C'mon...Rodney's parts aren't expensive.
You buy 4 ball joints and get 10% off. (100$ for all 4 ball-joints isn't expensive)
Then he came back on here and posted he needed all new components because they didn't last long.
Now that dude had to do the job all over again.

Like Blooze said, the CSI is mostly an overlooked sensor. Yes, they are available are are made from Bosch.
But they are expensive.Many fieros need a new O2 sensors. That's one good place to start.

I changed my MAP sensor with an upgraded one from GM. I'll have to get the part number out for reference.
Its has a different GM part number than the Fiero specific GM part number.

Everything has to be in top shape for excellent results.

I post the new GM MAP part number in a couple of days...

[This message has been edited by fierogt28 (edited 08-26-2013).]

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Report this Post08-26-2013 09:47 PM Click Here to See the Profile for FTF EngineeringSend a Private Message to FTF EngineeringEdit/Delete MessageReply w/QuoteDirect Link to This Post
I ran for years and years with my CSI completely disconnected and never missed it. YMMV, but I did not have the problem you guys are discussing.
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Report this Post08-27-2013 09:57 AM Click Here to See the Profile for Ry86GTSend a Private Message to Ry86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierogt28:

My 88s are well treated. Don't just start the engine and take off 1-2 minutes later. I always warm them up for 6-7 min.
Then before I leave, I wait for the RPM to drop at 1100, or 1000. When started they always idle at 1600-1700RPMs on cold
starts. Also remember that most people here may not of replaced most sensors, or could be still original.
One thing is, if you replace your sensors, replace them with quality sensors, not e-bay junk or used senors.
Buy them from a good known automotive parts store. Don't buy cheap parts, you'll get crappy results. Realistically when an engine
is out for overhaul, replace all the sensors. Its the time to do it...your there.

I keep telling people to stop buying parts off of e-bay, you have no service after buy from that site. Plus they think they are getting a deal
and get crap. If you buy, you have to know what you are getting. Just because the price is good, doesn't mean the parts are good.



This post has made me a tad defensive. My car is well treated as well, just because it has a problem it doesn't mean it's neglected. Quite the opposite, we're all here trying to sort it out. For the record every part that I have replaced I have replaced with brand new from reputable auto parts retailers, both online and locally.

I personally believe that it is not necessary at all to warm your car up for minutes before driving it, especially in the warm spring/summer/fall months (when my car is exclusively driven). You should be able to start and go within 15-30 seconds. The first thing I do when I get in my car is start it. Then I make sure I'm comfortable, put on my seatbelt, check my mirrors and put on the radio station of my choice. If I can't drive after taking 30 seconds to do that something isn't right. If your car is revving up to ~1,600 rpm and slowly dropping to 1,000 rpm then you do not have the issue that most of us in this thread are having. I bet most, if not all, of the others sharing my problem care for their cars very well as well.

As I said I personally do not believe that the issue has anything to do with the CSI - however I understand the logic previously explained by Blooze and appreciate his guestimate at the problem. I am more than interested in any possible solution to the problem.

With that said if anyone has a spare CSI switch and has the problem and is willing to swap it out to see if it makes a difference I am very interested in seeing the results. I know my CSI is working because I had actually deleted it. In my case it was taking so long to start the car that it didn't feel right so I re-installed it and the car once again starts up near instantly. I know it's working, whether it's working at full and intended capacity I don't know...

I am gearing up to go away for vacation for a week so I won't be able to tinker with the car for a bit, but when I come back and get a chance I am going to borrow a fuel pressure gauge again and see what that says on a cold start vs warm start.

I also want to investigate the IAC motor and it's circuit to make sure it's working properly.

The worst part of this issue is that it strictly occurs on cold starts, so I can only run so many tests and play around a little before the car has to sit and cool down completely. If there is one good thing, it's that it is not an intermittant issue.

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Report this Post08-27-2013 10:44 AM Click Here to See the Profile for Marvin McInnisClick Here to visit Marvin McInnis's HomePageSend a Private Message to Marvin McInnisEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Ry86GT:

Need some advice from the experts on where to start (well... continue) trouble shooting here.



This is a stock '86 2.8 V6, right? Everything you've posted suggests a fueling issue. I'm quite confident that it's NOT the CSI system, though, since, as you correctly observe, the CSI is active only during cranking.


 
quote

It runs a little different until it hits that certain point where you can tell it's warmed up - it just sounds like a switch was flicked and its running properly. The idle smooths out just a little bit, just enough to change it's tone a little. This usually happens about a minute or so after starting.



That's exactly what's happening. I think you're seeing the moment the ECM switches from open-loop to closed-loop mode. That's a big clue: Poor running in open-loop, but runs fine in closed-loop.


 
quote

I checked the fuel pressure and in my opinion it was borderline low, but the car is running fine (once warmed up...) and my experienced mechanic neighbour said it was ok and that the regulator was working. However I did notice that the fuel pressure drops pretty quickly after shut off.



Low fuel pressure will cause the problems you're describing. How much is "borderline low?" How are you measuring it? The GM spec is ~44 psig (3 bar, +/- 5%) with the engine not running. The pressure on your gauge should be lower (32-40 psig) with the engine running, as the fuel pressure regulator tracks manifold vacuum. Low system (battery) voltage can also cause lean fueling in open-loop mode. Have you checked the system voltage, at the battery, both with the engine off and with the engine running?

The drop in fuel pressure after engine shutoff is something to investigate. Possible causes are leaking injector(s), bad fuel pressure regulator, a bad fuel pump, or a leak in the fuel tank downstream of the pump. I'm not much for snake oil cures, but running some Techron through in a couple of tanks of gas might yield some improvement if a leaking injector or FPR is the problem. It probably wouldn't hurt to change the fuel filter (again) afterwards.

Beyond that, I would highly recommend using a scan tool (or WinALDL) to see what the engine sensors are telling the ECM. Pay particular attention to the IAT and CTS sensors. I know you said your IAT sensor is almost new, but it could still be bad or there could be a wiring defect. The scan tool should also confirm that your engine is smoothing out at the same time the ECM goes into closed-loop mode. High BLMs (values >128) will confirm that the ECM is adding extra fuel to compensate for a lean condition. There's no substitute for your own good data.

[This message has been edited by Marvin McInnis (edited 08-27-2013).]

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Report this Post08-27-2013 11:35 AM Click Here to See the Profile for Ry86GTSend a Private Message to Ry86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Marvin McInnis:
This is a stock '86 2.8 V6, right?

Yes, stock 2.8 V6. All that I've done is the tune-up maintenance described above, replaced the valve cover gaskets, refinished the plenum/valve covers, made my own vac lines out of aluminum tubing, relocated the PCV valve to the front valve cover and added some grounding. Essentiall a stock engine that's been tuned up and dressed up a bit.


 
quote
Originally posted by Marvin McInnis:
Low fuel pressure will cause the problems you're describing. How much is "borderline low?" How are you measuring it? The GM spec is ~44 psig (3 bar, +/- 5%) with the engine not running. The pressure on your gauge should be lower (30-40 psig) with the engine running, as the fuel pressure regulator tracks manifold vacuum. Low system (battery) voltage can also cause lean fueling in open-loop mode. Have you checked the system voltage, at the battery, both with the engine off and with the engine running?


The last time I checked when I was diagnosing my driveability issue I read 33/34 psi fuel pressure with key on/engine off and 30psi idling. My mechanic neighbour watched the gauge as I revved it a few times and said it was reacting as expected and that the FPR was regulating the pressure. I measured it with his mechanical gauge attached to the valve on the fuel rail near the coolant neck.

 
quote
Originally posted by Marvin McInnis:
The drop in fuel pressure after engine shutoff is something to investigate. Possible causes are leaking injector(s), bad fuel pressure regulator, a bad fuel pump, or a leak in the fuel tank downstream of the pump. I'm not much for snake oil cures, but running some Techron through in a couple of tanks of gas might yield some improvement if a leaking injector or FPR is the problem. It probably wouldn't hurt to change the fuel filter (again) afterwards.


My guess is that it's either my pump or the rubber hose in the tank has rotted. To my knowledge the tank has never been sropped on this car. Just last week I threw a can of seafoam that I had on my shelf into the tank to see if it would help with an un-related fuel sender issue. I agree it very well could be a fuel issue. I have a feeling I will be dropping the tank in the fall to clean the sender contacts at which time I would change the fuel pump while I'm in there.


 
quote
Originally posted by Marvin McInnis:
Beyond that, I would highly recommend using a scan tool (or WinALDL) to see what the engine sensors are telling the ECM. Pay particular attention to the IAT and CTS sensors. I know you said your IAT sensor is almost new, but it could still be bad or there could be a wiring defect. The scan tool should also confirm that your engine is smoothing out at the same time the ECM goes into closed-loop mode. High BLMs (values >128) will confirm that the ECM is adding extra fuel to compensate for a lean condition. There's no substitute for your own good data.


I agree, I need to pony up and buy a usb to aldl cable. I tried making my own a while back but failed. I could try and beg my neighbour to bring his scanner home again but I hate bugging him and begging for help lol. I'll try and see if I can make that happen when I return home from my vacation.

Thank you for the advice. I refuse to let this beat me.

[This message has been edited by Ry86GT (edited 08-27-2013).]

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Report this Post08-27-2013 12:43 PM Click Here to See the Profile for Marvin McInnisClick Here to visit Marvin McInnis's HomePageSend a Private Message to Marvin McInnisEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Ry86GT:

The last time I checked when I was diagnosing my driveability issue I read 33/34 psi fuel pressure with key on/engine off and 30psi idling.



That's a smoking gun right there. The GM spec is 44 psig (+/-5%), key on/engine off. Combined with the rapid loss of fuel pressure after turning the ignition switch off, it pretty much reduces the scope of possible causes to a either a defective FPR (least likely), a bad fuel pump, or a leak inside the tank. Dropping the tank to replace the pump is probably in your near future. I recommend replacing the OEM pulsator with a new one, too, but most people seem happy to get by using a length of submersible fuel hose (marked SAE J30R10).


 
quote

I could try and beg my neighbour to bring his scanner home again but I hate bugging him ...



These days many auto parts stores have scan tools in their loaner tool inventory. It costs nothing to ask.

[This message has been edited by Marvin McInnis (edited 08-27-2013).]

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Report this Post02-13-2014 12:30 AM Click Here to See the Profile for AL87Click Here to Email AL87Send a Private Message to AL87Edit/Delete MessageReply w/QuoteDirect Link to This Post
assuming that someone uses said submersible fuel injection hose in place of the pulsator.

where does the fuel in the line leak down from? back through the fuel pump if its bad?

I am pretty sure that if the fuel pump is good, the fuel wont leak down through it.
and assuming that the regulator is supposed to retain fuel and keep the line somewhat pressurized over a period of time.

am I right?
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Report this Post02-14-2014 04:35 AM Click Here to See the Profile for armosSend a Private Message to armosEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by AL87:

assuming that someone uses said submersible fuel injection hose in place of the pulsator.

where does the fuel in the line leak down from? back through the fuel pump if its bad?

I am pretty sure that if the fuel pump is good, the fuel wont leak down through it.
and assuming that the regulator is supposed to retain fuel and keep the line somewhat pressurized over a period of time.

am I right?


Yes, the lines normally hold pressure when it's shut off. When I checked mine a couple years ago it lost something like 4psi in 20 minutes. If it leaks down quickly then something is wrong.
Often it's a symptom of a leaking injector, including sometimes the cold start injector. But in this case the low operating pressure pointed to a bigger problem.

===

I didn't see this thread before, but I have another possible explanation based on my car.
My car has similar symptoms. Another detail with mine is that after the startup I can tell it's running rough. Once it gets past the hurdle of not immediately stalling, the IAC will open wide (I can sometimes hear it) just to keep the engine running at the correct RPM. Eventually the rough running/misfire dissipates and the idle speed surges to about 1500rpm. Then I hear the IAC close down and the idle becomes normal.

When I changed spark plugs last time, I tried dipping a piece of cardboard into some of the cylinders. I found one cylinder that had oil in it. I believe that cylinder is misfiring until the oil burns out.

[edit: since writing this, I now see that the stalling is a separate issue from the miss. When it stalls, all the sensor readings at the ECM have gone nuts. Looked at datalogs of a few different events and saw the same thing each time. So at least for my car this is probably caused by a bad ECM ground. Weird that it only happens a few seconds after starting though.]

[This message has been edited by armos (edited 03-10-2014).]

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Report this Post05-22-2014 09:26 PM Click Here to See the Profile for seqClick Here to Email seqSend a Private Message to seqEdit/Delete MessageReply w/QuoteDirect Link to This Post
Ry86GT, did you ever solve your issue?
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