I figured my words aren't effective enough to convey this problem I'm having with my throttle.
This problem only happens when stopped or creeping right on take off. the car wants to stall, and sometimes does with even the slightest bit of throttle input.
there is no issue at any engine speeds above 2k. I'm thinking its the tps being mal-adjusted, but no matter what I do; Even with new and known good-used tps' I put on, the car has this issue. (maybe injectors... MAYBE)
UPDATE: I finally went and tested ALL of the TPS sensors I have!
each one went from .04-5.04 volts exept for one (which was .11-4.89) over the full sweep of the sensor. they all tested consistent over the sweep test.
now when installed onto the throttle body the full sweep range cant be made. voltage test with the adjustment tab set neutrally at the manufacturer's setting yields a .83 at closed. and it shows 3.83 at full throttle.
is something wrong with this?
millivolts test to the ground wire shows signal. 0.00 key off. key on it spikes to 0.03 and then rests at 0.02 and is consistent. and signal wire shows 5.04V like it should.
I don't know what the problem could be.
[This message has been edited by AL87 (edited 11-23-2013).]
Could be off base here but ---- another forum member I know was having a similar issue - He found that his cruise control cable had a cracked mounting tab (It secured the cable firmly in place) and was affecting idle and drivability and sounded just like yours! We replace the cable and the problem was fixed.
I modified and regapped the plugs at .050 because I'm running an MSD 6AL ignition control box.
How long does the fuel pressure stay at 40 AFTER you turn the engine off? If you can see the gauge pressure bleeding off, you have a fuel pressure problem.
I've read lots of threads where people add aftermarket ignition stuff and it doesn't work right. Try getting rid of the MSD and going back to stock.
can anybody provide some sort of speculation as to what is going on here? I have this problem on my 87 GT as well.
I really don't know where to check. all I know is when I adjust the tps tab to where its not contacting the throttle body finger, and has some space, the engine's throttle response is as crisp as can be. exept that I sacrifice the torque convertor lockup.
the only code I'm getting is a 32, and that is because I deleted it. I've got all my grounds covered (with extra too) and nothing is blown, and everything works.
If you installed the MSD box with the GM wiring kit it is pretty easy to unplug the box from the coil and see if it that is the problem. I've done this a few times on my car to check the box.
When I had that problem, it was because my timing chain was loose and the chain guide had been destroyed... it would always jingle coming down to idle and it would hesitate off idle to the point that pulling out into traffic was scary.
Not easy to check and we had done everything else at that point... had no codes. We determined the with the chain in the condition it was in and resetting the timing afterwards, the cam was retarded by 8* due to the slack. The ignition timing was obviously subject to the cam timing. It all combined into horrible drivability, but it went like a raped ape on the freeway.
I've found a lack of response issue that bad is usually a MAP sensor issue. The ecm doesn't get the load change info, and so it runs like crap.
Do you have a winaldl setup or other?
Perhaps tap into the wiring to check volts vs kpa if you don't have a data reader. Look for near 5V with key on engine off (100kpa or so), and like 1-2 volts at idle (20-30 kpa typical).
If you installed the MSD box with the GM wiring kit it is pretty easy to unplug the box from the coil and see if it that is the problem. I've done this a few times on my car to check the box.
I've tried this. already with the msd, that is surely not the problem.
I'm also on a rebuilt motor, it only has about 15k on it right now.
I will try to test the map sensor, but how do I test it? with the diagnostic program? is there another way? or can I use a voltage tester
EDIT: swapped out the map from a vehicle that doesn't have this problem, and the issue still exists.
[This message has been edited by AL87 (edited 11-27-2013).]
1) Check the vacuum line going to the MAP for leaks. The MAP itself may be fine, but the source faulty. If you have a vacuum guage, place it where the map would go and idle your engine. you should see about -20 or so.
2) If the vaccuum is ok, then try a spare MAP sensor if you have one
3) If that doesn't work, remove the map sensor connector and test for voltage. There are 3 pins. With the key on, engine off, there will be 5v on on pin C (Grey), 0 volts on pin A (Check by placing red voltmeter lead on your + battery post and connect the black voltmeter lead to pinA, look for 12V)(Black/red), and pin B is open circuit (Lt gn); it's the signal sent to the computer by the MAP sensor.
If the +5, and common are there, re-plug your map in. Strip a short chunk of insulation off the B wire (lt gn), and connect a voltmeter; red to B wire, black to battery -. Go key on engine off. The signal should be near +5V. Start the car. The signal should be about 30kpa/100kpa*5v = 1.5Volts at idle. When you open the throttle, the voltage should spike close to 5V then back down as the engine speeds up, then to a really low value when you release the throttle (Briefly lower than the idle value), then move up to the idle value as the rpms come down.
You could still have a wire break between the map signal output and the ecm (C11 and C12). If accessible you could measure there without having to strip the B wire insulation. Or, just get a data computer and read the actual values and avoid all that hassle. Plus, check all your other sensors while you are at it!!
Chay
[This message has been edited by Slowbuild (edited 11-27-2013).]
Sounds like it could be a timing issue, as the engine doesn't run that smooth at idle either, and it sounds like combustion is still happening in the exhaust (timing not advanced enough). The balancer ring could have slipped, so when you timed it, you timed it to a bad mark.
The quick check is advance the timing 5* followed by 10* to see if it improves. The more accurate approach is to get a piston stop that threads into the spark plug hole. Then BY HAND bar the engine over until the piston stop makes contact with the piston (if you use the starter, it WILL put a hole in your piston). Scribe the balancer at the 0 mark. Then bar it over in the opposite direction until it makes contact again, then scribe the balancer at 0 again. Now you have 2 scribe marks and the true TDC is the midpoint between them. Make a new mark with some white out (or other highly visible liquid) at the true TDC location. Remove the piston stop, install spark plug, start the engine and check the timing to this new point.
A stumble at throttle tip in is almost always a lean condition issue (if its not timing). Bad TPS (controls A/E enrichment), bad MAP (controls fueling), or vacuum leaks are all likely suspects.
The engine coolant temp sensor controls cold start fueling, so unplugging it and adding a large resistor between the terminals will make the ECM think its really cold (25K = 0* F, 50K = -20* F) and dump more fuel. With a higher base fueling the stumble might be reduced and indicate it is a lean tip in issue.
I'll have to check and see if the harmonic balancer is off.
when I originally timed it, it was at 12*btdc. and then I moved it back to 10~9* btdc and now almost always does this thing just fire right up.
could I advance the timing even more to get a lower idle rpm? because this thing never wants to idle correctly any lower than about 1150 in gear. (A/T)
EDIT: It seems to be running just a tad rich at idle.
[This message has been edited by AL87 (edited 11-27-2013).]
It sound like the timing is way off. Is the harmonic balancer good in that the two rings, the inner and outer, are still solidly connected by the rubber isolator. The rubber can deteriorate and let the outer ring move in relation to the inner. I suspect the effect would be worse at low revs when each ignition pulse imparts a bigger 'thump' relative to the existing motion. At higher RPM it would all smooth out. Just a thought.
------------------ Anything I might say is probably worth what you paid for it, so treat it accordingly!
the rubber was fine, but I still think this may have taken another turn.
is it possible for the oxygen sensor to be out of calibration enough to tell the ecm the engine needs more fuel, without throwing a code?
I can see soot just coming out of the exhaust at idle. so I believe that any throttle input dumps an excessive amount of fuel into the combustion chamber... thus almost flooding the engine.
Sounds like it could be a timing issue, as the engine doesn't run that smooth at idle either, and it sounds like combustion is still happening in the exhaust (timing not advanced enough). The balancer ring could have slipped, so when you timed it, you timed it to a bad mark.
The quick check is advance the timing 5* followed by 10* to see if it improves. The more accurate approach is to get a piston stop that threads into the spark plug hole. Then BY HAND bar the engine over until the piston stop makes contact with the piston (if you use the starter, it WILL put a hole in your piston). Scribe the balancer at the 0 mark. Then bar it over in the opposite direction until it makes contact again, then scribe the balancer at 0 again. Now you have 2 scribe marks and the true TDC is the midpoint between them. Make a new mark with some white out (or other highly visible liquid) at the true TDC location. Remove the piston stop, install spark plug, start the engine and check the timing to this new point.
A stumble at throttle tip in is almost always a lean condition issue (if its not timing). Bad TPS (controls A/E enrichment), bad MAP (controls fueling), or vacuum leaks are all likely suspects.
The engine coolant temp sensor controls cold start fueling, so unplugging it and adding a large resistor between the terminals will make the ECM think its really cold (25K = 0* F, 50K = -20* F) and dump more fuel. With a higher base fueling the stumble might be reduced and indicate it is a lean tip in issue.
finally got back around to testing here, I haven't done a true tdc marking procedure yet, but the ring looks good and comparable to another one sitting here.
ONE thing though that is extremely noticeable... the car runs rich, at least enough to make the exhaust really sooty...
there cannot be any vacuum leaks, I triple checked... and the tps seems to be alright... so I'll have to check the map now.
I overhauled an engine, and put it in, and used the same harness, the car ran right for the initial test drive, and 30--45 minutes later the icm popped... I put a backup in for now, but a little before the icm popped it was starting to stumble. again...
it's been a while since I worked on a 2.8L... But have you checked your EGR? it's idling high and running like crap, sounds like the EGR may be stuck open... or the problematic EGR tube..
Also, what mods do you have to this engine? From your video, I had to double check your post and make sure it was a 2.8L because it idles like a cammed v8....
it's been a while since I worked on a 2.8L... But have you checked your EGR? it's idling high and running like crap, sounds like the EGR may be stuck open... or the problematic EGR tube..
Also, what mods do you have to this engine? From your video, I had to double check your post and make sure it was a 2.8L because it idles like a cammed v8....
Originally posted by AL87: somewhere in the wiring... or in the ecm...
JUST for the laughs and giggles... I put in a spare ecm from another v6, and guess what? it runs just fine, I'm going to proceed with further testing and adjustment.
JUST for the laughs and giggles... I put in a spare ecm from another v6, and guess what? it runs just fine, I'm going to proceed with further testing and adjustment.
So replacing the ECM fixed the issue in the video while everything else failed? Have you tried reseating the connections of the old ECM and visually inspecting how the pins look? Maybe the connecting traces are corroded or worn out?
Cause I've got the same problem. Replaced pretty much everything, cleaned everything and have no clue what's left. Didn't touch the ECM though... But spending over $150 plus shipping to my place to "just see" if the ECM is the problem is kind of big money. Is there any way to test a defective ECM in this kind of situation?
Cause I've got the same problem. Replaced pretty much everything, cleaned everything and have no clue what's left. Didn't touch the ECM though... But spending over $150 plus shipping to my place to "just see" if the ECM is the problem is kind of big money. Is there any way to test a defective ECM in this kind of situation?
my question (at this point) exactly^^^
Im lucky I have spares... it would be a whole lot easier for me to have them all tested... I've got so many spare parts just laying here...
Upgrade to a 7730. Bound to be a bin code that will be a base start for your combo. And probably still run better than the poor original ECM trying to run an engine that has altered flow, higher max flow and therefore different timing and fuel curve requirements. Can't imagine trying to get a stock ECM to run such a modified 2.8. Are you planning on getting tuning equipment or sending a readout to somebody to do a custom tune? Above you mentioned getting a read using a laptop.
Upgrade to a 7730. Bound to be a bin code that will be a base start for your combo. And probably still run better than the poor original ECM trying to run an engine that has altered flow, higher max flow and therefore different timing and fuel curve requirements. Can't imagine trying to get a stock ECM to run such a modified 2.8. Are you planning on getting tuning equipment or sending a readout to somebody to do a custom tune? Above you mentioned getting a read using a laptop.
eventually, for about 200 bucks I could have a complete setup; 75 for a workhorse laptop, another 65 for the software/cable. and about 60 for the flashing/writing equipment.
Upgrade to a 7730. Bound to be a bin code that will be a base start for your combo. And probably still run better than the poor original ECM trying to run an engine that has altered flow, higher max flow and therefore different timing and fuel curve requirements. Can't imagine trying to get a stock ECM to run such a modified 2.8. Are you planning on getting tuning equipment or sending a readout to somebody to do a custom tune? Above you mentioned getting a read using a laptop.
But he did replace the ECM and fixed it all. Anybody has any ideas concerning the ECM testing? Don't want to throw $200+ bucks just for the sake of checking if it'll change anything or no.
My 4 cyl car had similar symptoms and it was the new EGR, it apparently worked too well. While it was installed I got excellent mpgs but at the price of the symptoms described. Replaced it again and no issues.(However I'm not sure if 2.8 EGRs work quite the same.)
My 4 cyl car had similar symptoms and it was the new EGR, it apparently worked too well. While it was installed I got excellent mpgs but at the price of the symptoms described. Replaced it again and no issues.(However I'm not sure if 2.8 EGRs work quite the same.)
mine was completely deleted... and the wiring for the solenoid was jumped so it wouldnt throw a code.
