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Runs rough when cold by Super Duty Critter
Started on: 06-07-2012 09:57 AM
Replies: 85 (2519 views)
Last post by: 2kewlgypsy on 04-07-2014 01:40 PM
Super Duty Critter
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Report this Post06-07-2012 09:57 AM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have a 1988 Fiero GT. It has 45,000 miles that I recently bought it from a gent who said it has set up for long periods of time. When we test drove it the car ran horribly but he said the gas in the tank was at least 4 years old. I'm now on the second tank of fresh gas and I've put a can of SeaFoam in as well. It is indeed getting a little better but what I've noticed is that the car is slow to start, seems to miss and stumble with a few pops through the exhaust and then it all smooths out once the car is fully warmed up. I intend to do some throttle body cleaning this weekend but what other suggestions do you folks have to help me iron this out?
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Report this Post06-07-2012 10:28 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
There is still junk in your fuel system....There are probably bad contacts in your electrical system too.

There is a professional-grade 'sea foam' type system that is a bit more serious and helped my car a lot a few years ago. You may give that a try... Ask a shop about it. Otherwise I would suggest doing it over a few times and things will get better.
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Report this Post06-07-2012 10:38 AM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
Any idiot lights lit?

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Report this Post06-07-2012 10:46 AM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
No, it's not throwing codes. The previous owner did say it took 3-4 tanks of gas to smooth out so there is some merit to the comment of trash/bad gas. I intend to fill it up again this weekend and dump another can of SeaFoam in. I'm also planning on using some throttle body cleaner to do a general cleanup of that area in case there's any buildup hanging the blades open.
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Report this Post06-07-2012 10:57 AM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
Bad injector maybe.
Car could need a regular tune up too.
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Super Duty Critter
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Report this Post06-15-2012 09:23 AM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
Back to the top with this one.

After extensive research in this forum and another tank of gas I decided to change the MAT and CTS. I also removed and cleaned the IAC. The car is better. The idle is rock steady at 750 RPM after it warms up and throttle response is much better. But I still have to crank for a long time to get it to start and it still stumbles until it warms up. Change the fuel filter next?
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Report this Post06-15-2012 09:35 AM Click Here to See the Profile for FieroJamClick Here to Email FieroJamSend a Private Message to FieroJamEdit/Delete MessageReply w/QuoteDirect Link to This Post
Have you thought about checking the fuel pressure? My 87 GT was taking lots of cranking to get started but ran decent after starting and it ended up that the fuel pressure was only around 16PSI at start up and only would get to around 21PSI when running. The fuel pump ended up being the issue. Just something else to check.
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Super Duty Critter
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Report this Post06-15-2012 10:09 AM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
I did consider that but figured I needed to eliminate a plugged up fuel filter before checking the pressure. My logic there is that it had old gas in it and I'm now on the second tank of gas with SeaFoam in it. I wondered if I've knocked enough varnish and crap loose that I'm plugging the filter?
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Report this Post06-15-2012 10:14 AM Click Here to See the Profile for crashyoungClick Here to Email crashyoungSend a Private Message to crashyoungEdit/Delete MessageReply w/QuoteDirect Link to This Post
Forget the seafoam, I have switched to chemtool products. I also ran two cans of seafoam through my tank, but it still didn't help any, I used one can of chemtool in the gas, and I HAD to change the filter, lots of varnish and trash in the filter...
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Report this Post06-15-2012 10:36 AM Click Here to See the Profile for Fiero84FreakClick Here to Email Fiero84FreakSend a Private Message to Fiero84FreakEdit/Delete MessageReply w/QuoteDirect Link to This Post
I don't think it would hurt to change the fuel filter out. It's easy to get to. Lower firewall on the passenger side of the car.

Does the same cranking syndrome occur when it's been ran and warmed up or is it only when it's cold?

[This message has been edited by Fiero84Freak (edited 06-15-2012).]

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Super Duty Critter
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Report this Post06-15-2012 11:04 AM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
The long cranking syndrome happens hot or cold. There are times when it hits immediately but they are few and far between and usually after I shut down and immediately start it back up.

I've used the Berryman's Chemtool in the past. It's worked well for me. That was in a pickup truck that had some issues with carbon build up. The early Vortec motors were bad about building up carbon and would sound like a diesel when they started. One can of that stuff and it went away for a few months.
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Report this Post06-17-2012 07:42 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
Changed the fuel filter. I also used air pressure to back blow the fuel line to the tank. No change. Should I check fuel pressure next?
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Report this Post06-17-2012 07:57 PM Click Here to See the Profile for Francis TClick Here to visit Francis T's HomePageClick Here to Email Francis TSend a Private Message to Francis TEdit/Delete MessageReply w/QuoteDirect Link to This Post
Since it runs smooth when warmed up you can probably rule out most of the above mentioned items -like filters- as they should also cause problems when warm. Try cleaning/and/or replacing your o2 sensor. Whereas the Fieros use 2 wire o2 sensors -with no heaters- a dirty one can take too long to reach operation temps.

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Report this Post06-17-2012 08:22 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
Good thought. I'll give it a shot.
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Report this Post06-17-2012 08:45 PM Click Here to See the Profile for firejo24Send a Private Message to firejo24Edit/Delete MessageReply w/QuoteDirect Link to This Post
Careful with “back blow” into the tank. The fuel pump has a check valve you can damage if you give it to much pressure. I’m guessing (from what you described) is that the injectors are probably gummed up. Fuel injector cleaner might help a lot but you might also be looking at injectors. If you have a scan tool go in and see what the “BLM” is at. It should be close to 128 meaning that the ECM isn’t having to compensate for a rich or lean condition. When the engine is cold and in open loop, the ECM can’t, except on a limited basis, compensate for much (like dirty injectors). When it warms up and goes into closed loop then the ECM can deal with a rich or lean condition thus it starts running better. If the BLM is above 128 the ECM is adding fuel (I’m guessing this is what you’ll find) and if it’s less than 128 it’s taking fuel away. When you’re dealing with a car that has been sitting for a long time this is always a good test to run just to get an idea where the ECM is when it’s in closed loop. Also, when injectors sit for a long time the fuel that’s in them will caramelize (not really but it’s the same effect) and plug up the orifices causing a bad spray pattern. Do replace the fuel filter. It’s full of gunk as well.
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Super Duty Critter
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Report this Post06-17-2012 09:01 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
I don't have a scanner but was looking at the WinALDL stuff last week. I'm guessing that the cable and my laptop my give me information needed. But that has to be low on the priority list right now. Replacing my stolen truck, trailer and buying the new Fiero have but a serious bite on the bank account. But it is most certainly on the list.

I sure see what you're saying about injectors though. When I replaced the filter I noticed that there was some gunk. Could very well be it. The O2 sensor is easy, so I'll do it first. Probably couldn't hurt to replace it anyway. Then I'll move on to trying your suggestion. I know a guy who might have a scanner I can borrow.
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Report this Post06-18-2012 04:31 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
there is gonna be quite a few seperate issues you need to take care of.
Techron is a great fuel additive to help clean the system, but, likely wont be enough
there is also the likely crusted over temprature sensors
dried out ignition wires
crusty distributer cap

one thing at a time.
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Report this Post06-18-2012 05:11 PM Click Here to See the Profile for 86gtblakjakSend a Private Message to 86gtblakjakEdit/Delete MessageReply w/QuoteDirect Link to This Post
Try putting 5.3oz of Seafoam through the vacuum line on the brake booster. It worked for me. Here is a video for how to do it not me just an example. http://www.youtube.com/watch?v=q6bzb4FHqds
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Super Duty Critter
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Report this Post06-18-2012 09:35 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
I agree. Mulitple issues are what I'm facing. So far I've replaced the MAT, CTS and O2 sensors along with cleaning the IAC and throttle body. Every time it gets a little better. Tonight I'm going to go out after dark and fire it up to see if it see I spark show on the engine. I'm betting the plugs and wires are original.

I've put 2 bottles of SeaFoam through the gas tank and now changed the filter. I might try the booster trick but for now I'm chasing the stumble in a more traditional way.
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Report this Post06-18-2012 10:29 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
No spark show so I'll check fuel pressure next.
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Super Duty Critter
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Report this Post06-19-2012 07:08 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
The new O2 sensor really seems to have helped. It still stumbles when cold but isn't doing the small backfire nearly as often. It also seems to warm up faster and smooth out sooner.
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Report this Post06-20-2012 05:46 AM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonEdit/Delete MessageReply w/QuoteDirect Link to This Post
I didn't see any mention of spark plugs being replaced or checked, if they are the originals after all these years it's a good place to check also. Rough idle on startup that smooths out as the car warms to operating temp could possibly be clogged injectors as the motor maybe a little on the lean side at startup smoothing out as inlet air temp increases becoming less dense and easier to reach the commanded air fuel ratio.

I experience it everyday since I haven't experimented with my tune enough to sort it out. I can watch the initial startup AFR on the data dash around 15:1 start to decay out after startup and the engine smooth out as it approaches about 12.5:1 where the roughness disappears.

Check your timing also as cold to warm startup usually has more advance programmed in until operating range temperature is reached which is pulled as the engine temp starts to increase toward operating range. If the base timing is too far advanced the additional startup advance maybe too much and that will cause an initial rough running engine until the cold/warm start timing is pulled.
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Super Duty Critter
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Report this Post06-20-2012 09:21 AM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
No, I've not looked at the plugs yet, but I guess I will this evening after work. I went out this morning and it wouldn't start. Ran like a champ yesterday on the drive home so I parked it and walked away thinking I'd let it be until the weekend. I guess she didn't like not getting any attention last night.

Symptoms are, it cranks, no movement on the tach, never fires. I didn't have time to start trouble shooting this morning. I know it takes fuel, air and spark so I'll start with spark tonight. Might be an ICM?
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Report this Post06-20-2012 09:41 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
Had the wife crank it to check for spark. Fired right up on five cylinders and ran like a champ. WTH?

And as quickly as it miraculously healed itself, it died again. More testing pointed to the ICM so I yanked it and went to the parts store. It failed 4 out of five tests. Jammed a new one in, started right up and I drove it around for a while to be sure. It restarted after it was hot so that's a good sign. FInal proof will be in the morning when I crank it up to go to work.
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Report this Post06-20-2012 10:04 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
ICM.....

did you get the right goop to put under it? or did they sell you the clear stuff?

[This message has been edited by Gall757 (edited 06-20-2012).]

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Super Duty Critter
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Report this Post06-20-2012 10:26 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm an IT guy by trade these days. We use thermal paste on heat sinks for processors in the computers we support. The best stuff I've found comes from Radio Shack. That's what went under it. If somebody want's the made in China stuff that came with it I'll mail it to them.
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Super Duty Critter
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Report this Post06-21-2012 09:30 AM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
Cranked right up this morning and made the 15 mile drive in to work.

While I was puttering around with it last night I did the "prime it, press the Schrader valve" fuel test. Got a healthy stream so I don't think I have a fuel pressure problem. The hesitation is still there, but not as bad as it was when I started this thread. The biggest change was the new O2 sensor. I'm running out of ideas. I still need to check the timing. What about a weak coil or bad TPS?

[This message has been edited by Super Duty Critter (edited 06-21-2012).]

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Gall757
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Report this Post06-21-2012 09:38 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Have you changed the spark plug wires? They should be shot from all that sitting, and they may have been a reason for the bad ICM.
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Report this Post06-21-2012 09:49 AM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
Not yet. I'm trying to do one thing at a time to see what fixes it. But it's on the list. I pulled a plug to check for spark last night and noticed it has Bosch Platinum plugs. I seem to remember reading somewhere in the archives that this was a bad choice for the V6 Fiero. The plugs look brand new but I'll change them if folks think that might be a problem.
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Report this Post06-21-2012 10:01 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Yes...a bad choice.

Most people can tell the difference immediately when they switch back to stock plugs.
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Report this Post06-21-2012 09:24 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
Ran like a sewing machine on the way home from work. Just the tiniest stumble when I started it. But the temps were in in the mid-90's here today. It's weird. If the air temp is in the 90's it seems to smooth out.

And I have to say, I do love driving a Fiero. They're unique and handle well in traffic. It's just more fun than driving one of those foreign built cars where they all look like they came from the same mold.
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Report this Post07-04-2012 08:26 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
I've let this drop for a bit since I was working on the air conditioning. Got that resolved today but it's running worse than ever so I'm back to this.

To update, while I was doing the AC I removed the catalytic converter. It was shot. I replaced it with a straight pipe that welded in place. AC was a new compressor, accumulator, orifice tube and charge.

I just came if from doing a fuel pressure test. I had 40psi only priming it. It hung around 36psi at idle and would spike up to about 40 or so when I'd apply throttle. Of course it wouldn't break up for me because it was warm from driving it around doing the AC testing. But I did get one really bad stumble and I noticed the fuel pressure went up to 45psi when that happened.

All of this stumbling happens with part throttle application. If I get aggressive it downshifts and pulls right through it.

So I'm thinking I should test the TPS and MAP sensors next? Does that sound like a good idea?
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Report this Post07-05-2012 07:08 AM Click Here to See the Profile for PhirewireClick Here to Email PhirewireSend a Private Message to PhirewireEdit/Delete MessageReply w/QuoteDirect Link to This Post
From my experience of gas issues, when you buy a sitting car, don't run it with bad gas drain it. Its been sitting, eating at tank, going "stale". Drain it, check it put in fresh (higher octain than standard). If it hasn't been sitting long put in octain booster or just mix with a higher octain.


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Report this Post07-05-2012 09:15 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 Super Duty Critter:
I just came if from doing a fuel pressure test. I had 40psi only priming it. It hung around 36psi at idle and would spike up to about 40 or so when I'd apply throttle. Of course it wouldn't break up for me because it was warm from driving it around doing the AC testing. But I did get one really bad stumble and I noticed the fuel pressure went up to 45psi when that happened.

Your fuel pressure sounds normal to me. The fuel pressure regulator maintains consistent fuel pressure relative to the manifold air pressure. When you open the throttle the manifold air pressure increases so fuel pressure will go up as well. When it had the bad stumble, the engine wasn't pumping air as effectively, so pressure built up in the manifold and fuel pressure went up in proportion.

If you haven't replaced those spark plugs yet, that would be the next thing I'd buy before anything else. The basic ACDelco R42TS copper plugs are best and cheap. The Bosch Platinum are controversial for causing people problems sometimes, and not only on this car.
The TPS is pretty straightforward to test, but the MAP sensor is hard to do much with. If you unplug the MAP and the car runs much better, then that's an indicator.
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Super Duty Critter
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Report this Post07-05-2012 09:19 AM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
I do have six brand new AC Delco plugs on the bench, ready to go in this weekend. I was planning to back probe the TPS and MAP sensors tonight. I have a digital meter and and vacuum pump so I figured I'd do that, then swap plugs this weekend.

Thanks to everyone here for all the suggestions. It really helps to have folks with a breadth of knowledge to ask for help.
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Report this Post07-05-2012 08:42 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
Tested the TPS and MAP sensors. Both passed. I moved on to changing plugs. I decided to test wires for resistance while I was rolling along. Everything was showing 6-7 ohms. Then I got to #6 plug wire. Nada. Not a thing. Maybe that's a problem? LOL.
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Report this Post07-05-2012 09:26 PM Click Here to See the Profile for RWDPLZClick Here to visit RWDPLZ's HomePageSend a Private Message to RWDPLZEdit/Delete MessageReply w/QuoteDirect Link to This Post
Could be. Those are REALLY low resistances for plug wires, are they MSD's or something?
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Super Duty Critter
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Report this Post07-05-2012 10:00 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm not sure what brand they are. The stuff printed on the side says "7MM Double Silicone Heat Resistant - Made In The USA". Gay in color with black boots.
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Report this Post07-06-2012 09:24 PM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
I changed all the plugs and wires tonight. To the fellow who put in five Bosch plugs and left that one original AC plug on number 2 may you rot in hell for your shoddy work.

The car started much better but as soon as I hit the throttle i had the old stumbling and backfiring through the exhaust. I really paid attention tonight while I ran it around the neighborhood. This problem is manifesting itself at 1200 rpm by the TAC in the car. It stumbles, backfires and then catches itself up and goes on. If I go wide open throttle I don't see it. If I go half throttle I dont see it.

Even though it tested OK with the volt meter I wonder if this is a TPS? Opinions?

[This message has been edited by Super Duty Critter (edited 07-06-2012).]

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Super Duty Critter
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Report this Post07-07-2012 10:13 AM Click Here to See the Profile for Super Duty CritterClick Here to visit Super Duty Critter's HomePageSend a Private Message to Super Duty CritterEdit/Delete MessageReply w/QuoteDirect Link to This Post
So far I have run 2 cans of SeaFoam through the fuel system, replaced the fuel filter, replaced the air filter and the MAT, CTS, Oxygen sensors. I cleaned the IAC and throttle body I've tested the TPS and the MAP sensors. I've replaced the ICM and all plugs and plug wires. I also hooked up a vacuum pump to the EGR to be sure it's moving the pintle in and out.

This morning I ordered an ALDL cable and will move on to hooking up a laptop. Maybe that will help point me. I'm running out of ideas. All suggestions are welcome.
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