My pesky 86 GT V6 has been giving me fits. It runs smoothly when first started and idling in open loop mode. However, once it hits closed loop mode, it starts to run rough and will stall without warning, especially when the idle is below ~1,500 r.p.m. or so. I've noticed it tends to idle a bit better in test mode with 1 & 2 bridged on the ALDL, which may point to timing. However, here's what I have noticed. Sometimes after it stalls, it will be quite difficult to start, much like the battery is dying. However, the car can run for quite some time without stalling, and the battery tested 100% at O'Reilly Auto Parts when I removed it from the car and had it tested. I feel fairly sure there is some sort of ignition or electrical issue causing the stalling.
I think it's worth noting that I was replacing the exhaust manifold gasket on the trunk side, and the issue didn't exist before this. After replacing the gasket, the issue appeared, even though the gasket install went fine and suppressed some of the exhaust noise.
I've also noticed hesitation, stumbling, and even no acceleration at full throttle with this issue. It also won't rev any higher than about 3,500 - 4,000 r.p.m.
Here is everything I can think of that I've done to the car to work on the problem to this point:
* Replaced idle control module with the pintle at the throttle body and cleaned housing * Replaced broken plug connector at the MAP sensor on the intake manifold * Set timing * Checked for vacuum leaks three times with fogger, propane tests * Tested ignition module under heat at O'Reilly Auto, tested fine (I put heat sink compound on it when I reinstalled) * Quick tested EGR valve by pressing up on it during idle. It stalled the car when pressed upward. * Alternator seems to be working since the car can idle indefinitely sometimes. Could be a charging issue though. * Checked voltage at injector rails. Shows ~1.5 volts on two connectors, ~12 volts on the third. * Fuel pump turns on for ~2 seconds when the key is first turned to run mode.
I've also replaced the rotor button, distributor cap, spark plug wires, and plugs, air filter, cleaned air filter housing, cleaned throttle body and associated ducts, but did those things before this issue started.
When cranking does it start to crank, and then stop and then start cranking again? If so that indicates you have too much initial advance. Turning the distributor clockwise will retard it. Do it just a little.
What is happening is when a cylinder fires it is still way too far before TDC. The firing cylinder tries to turn the engine backwards and fights the starter. When the engine is cold the firing cylinder produces not as much power. Warmed up the firing cylinder produces more power.
The fact that it runs better with A-B jumpered also indicates too much advance.
You should set the timing with a timing light but just bumping it back should take care of this immediate problem.
Note also - It is possible for the outside of the balancer to slide vs the inside of the balancer. If it does that your timing marks will be off. If the ring looks like it is separating that can cause the mark locations to be for crap.
[This message has been edited by phonedawgz (edited 03-15-2014).]
What bothers me is your statement about the voltage on the injector plugs. If you where measuring on the connectors that go to the injectors you should see 12V on one of the pins to a ground on all plugs. The other pin should be a ground provided by the ecm while it's running. So checking the ecm pin the reading could vary. The Fiero uses bank fire of injectors so all the even injectors fire at the same time and all the odd fire at the same time. (only 2 ecm putouts for fuel.even/odd) I.E. All the even plugs should have 12V on one pin. The other pin should measure a connection between all the like pins with all three going to one output of the ECM. Same with the odd side.
So while it could be timing it can also be other things. Once your in closed loop all the sensors are used for engine running. A bad reading from the TPS or CTS can also cause problems. If you can get your hands on a scanner you could check out the sensors.
[This message has been edited by Dodgerunner (edited 03-15-2014).]
Phonedawgs, it does indeed sometimes start to crank, stop cranking, them start cranking again. I bumped the timing back, but it still cuts off once it starts getting warm. I noticed today that it cut off in about two minutes of operation from a cold start. I've got a timing light, and I'll be sure to check it for 10 degrees BTDC.
I got the fun code 35 due to the poor idle. I've already replaced the idle air control valve, and I don't suspect the EGR (yet) since it isn't supposed to be commanded on by the ECU when idling in park.
Any other thoughts as to what might be happening? This has been so frustrating; I'm almost ready to start driving it again, but can't until this shut off business is fixed.
When it stalls does the SES light come on before the engine stops turning? If so I'd say try replacing the ECM. You can try advertising for one on the Forum for one close by. I'd be willing to sell one for $40 + 5 shipping.
When it dies it dies like it's an electrical problem. No coughing. When you swung the camera over the check engine light was on. It should be if the key is on, but the engine isn't running. Since we watched the tach drop to zero the film shows a normal operation. I suspected perhaps the ECM was loosing power to it but then the SES light wouldn't be on, so that seems to be eliminated.
Since it dies so nice it might be worth it to buy one of my scan cables and watch carefully when it dies. You can set TunerPro RT to record so you then can drill back and see which if anything wacks out first on the scan data
Normally, the CEL doesn't come on. It'll be running ok, then suddenly and abruptly cut off during idle. I'm also convinced that something electrical is at fault, especially with the trouble with restarting.
It's really kickin' my ass. I'll dig into the timing again tomorrow to see getting the timing fine tunes helps. This problem only manifested itself when I was working on the manifolds, but I suspect it really started when the distribution got rotated when the hold down bolt was left unsecured by the previous owner.
Thanks to everyone that had contributed ideas so far! Please keep 'em coming until we get this Fiero back on the road!
If you leave AB jumped while it's running and warned up does it stay running? Doing that changed some parameters othe then timing. I'm also wondering if once it goes into closed loop and timing control takes over if it's jumping to a point where it can't run. Just spit balling ideas. Like if you base timing is advanced so far (maybe TDC being off) it runs in open loop but once in closed it jumps so advanced that it can't run anymore. You mentioned it won't rev above 4K. That is also a symptom of timing too advanced. ( I think)
You guys are great, thanks for keeping up with this with me!
I've figured out that I can't turn the distributor enough to get the timing to calm down. I've had to turn it so far counterclockwise that I've run out of turning room. The ICM is pressed against the intake manifold, blocking me from turning it any further. I'm guessing I've got something misaligned with TDC and the rotor pointing toward #1, but can't figure it out. What am I missing here? Will I need to remove the distributor to reset all of this mess?
I've also noticed that sometimes the chime for the headlights being left on or the key in the ignition will be strangely weak sounding and quiet. It sounds like what I would expect it to sound like if it wasn't getting enough voltage. I wonder if it is a symptom of the same issue that is causing the car to abruptly cut off.
Sounds like your off one tooth on the Dist. Are you rotated all the way CW or CCW hitting the Manifold. If your all the way CW (plugs pointing to the left side of the car) then you need to pull the dist out and move the shaft one tooth CCW that should allow you to put your ICM plugs toward the left rear tail light.
You might measure the voltage on the ALDL plug and see what it does while running. Measure from the A pin to the G pin. That will be voltage going to the fuel pump. Will do 2 things for you. Can see if the 12V stays around 12V or more and see that your fuel pump continues to get voltage when it dies.
Thanks Dodgerunner. I can live without the blue dingy, but sure can't have much fun without the car being able to pull out of the driveway on its own power. Any other ideas about why it keeps cutting off? Bad grounds? Bad timing still? Something else electrical? Thanks for keeping up with this thread, it really helps.
You need to start troubleshooting. Guessing at ideas is a very inefficient way to solve problems.
1 - Hook up your timing light and run the engine till the trouble occurs. When it does, does the timing light stop flashing when the cutout starts? Yep it's going to take some time and concentration. You might try video recording it in case you miss the event. If the light stops at the start of the event then look at ignition. If not look at injection. Yes the light will stop flashing once the engine stops. The question is does the light stop at the start of the problem and stays out while then engine is spinning to a stop.
2 - If the ignition isn't failing then test the injection system. Purchase one of these http://www.harborfreight.co...09.html#.UyiHVahdUrc - Computer Safe Automotive Logic Probe. It must be a powered test light light this with two leads for the battery and a probe. It is sensitive enough to see the injector pulses. Get a set of alligator clip wires also so you can connect this up without having to hold it in place. Then stick a pin into the 6 pin injector harness - engine harness connector - Connect it to either the Lt. Blue or Lt. Green wire. One is each bank of injectors.
Connect both the red and black of the powered logic probe to the battery. Then using the alligator clip wire connect the probe tip to the pin you stuck into the connector. The probe should flash one light each time it fires the injector. The other light will be on when the injector is not being fired. If you don't see this play with the inserted pin until you get it in far enough in and touching the metal inside so you can watch the injector pulses. Again watch/record and watch for the failure. Does the light stop flashing injector pulses at the start of the problem while the engine is still rotating?
Note - You need to do the ignition test before the injector pulse test. The ECM senses ignition pulses to fire the injectors. So if the ignition is what is failing, you will also get a fail on the injector test. Thus you need to confirm it is not the ignition before proceeding to testing the injection system.
I watched the timing light for issues when the problem starts. It certainly seemed to me that there was a momentary loss of flash on the timing light at #1 when the event started. I made some timing adjustments with the distributor, and the problem generally, but not completely, seemed to go away. It did surface once more, IIRC, but the last time I ran the car for the night, it idled for 20 minutes straight without cutting off.
I went to test it again and to quickly see what the FI pulses looked like with the probe. Naturally, they looked fine since the car was idling, mostly correctly.
I still notice some occasional slow cranking issues once the car is warm, even though the battery charger/tester says the battery is charged up and O'Reilly Auto said it tested to 100%. Interistingly, the blue dingy thingy seems to be happier when the car starts quickly, and vice versa. I'll pay close attention to this tomorrow so I'll know if the sound issues with the BDT are related to the slow crank issue, possibly indicating a global electrical issue in the car rather than a localized one. I ran a new ground from the body to the block just to add a bit of strength to the ground system. No change yet.
I went to put the car in gear to test things under load, but regrettably, the A/T shift cable seems to have either broken or become disconnected. A whole new bag of fun with this car. I'll do some research to look up the "zip tie" repair, hoping that it is that simple. Otherwise, it might be new cable time, which I understand is quite the bag of hurt.
I'll run the tests again tomorrow to see if the idle remains stable. One day, one day, I will drive this car again.
Made a quick edit to add that I see some white smoke coming from the firewall side of the engine on occasion. It a light amount, but it's being expelled with force, so it seems clear it's exhaust related.
Thanks again for everyone that has been helping me out. I'll post back soon with any new updates on the issue.
[This message has been edited by blainelocklair (edited 03-20-2014).]
More testing tonight on the ignition side. Here's a video of the timing light flashing on the carpet. It goes into slo-mo 120fps at around the 12 second mark, and around 30 seconds the car starts to cut off on its own. Note the flashes at that time, and see what you think.
Also, on an aside, I fixed the tranny cable. It had come loose in the engine bay where it meets the shift lever.
It looks to me like it's still trying to spark as the engine starts to die. However, as it idles down, it's not sparking on the way out. Any other opinions or thoughts on this?
While I have never used a noid light I don't know what the pulse flicker should look like. However you have to remember the ecm is changing the pulse duration and frequency all the time. So unless you can compare to another engine I'd not jump to conclusions. Unless someone else knows for sure. Can't remember have you tried a different ecm yet?
I noticed that you had the module checked, and it according to the test at the auto parts store, it was good so you put it back in.
I do not have any experience with the 2.8 ignition module (my Fiero has the SC3800II) but over the years I've read that others had the same test show good at auto stores, only to replace the module later and find their issues resolved.
I do not normally advocate blindly replacing parts, but in this instance, I think I'd set my mind at ease and spring fro a new GM ignition module.
Well, I think either the head gasket is blown or the block or head is cracked. I tested it with a combustion test kit, and didn't get a chemical change to yellow, but the engine has many signs of being blown.
First, it overheated on my trip home with it from NC to the point of coolant boiling. Second, it leaks white smoke from the firewall side of the engine bay. Third, it refuses to stay running, even with timing, ignition, and fuel verified. Fourth, it seems to be losing coolant, in spite of not dripping it out. Fifth, it overheated again in my garage, even with the thermostat out. Sixth, it makes a fancy puddle of oil underneath it. Not like a slow drip, like a puddle in a few days or less. Seventh, I can barely stand to look at the timing marks because the fumes from the engine bay burn my eyes and give me a headache. I'm pretty sure this is an exhaust leak from either the manifold or a crack in the engine somewhere.
Well, that's what everything I have that makes me suspect this poor running problem is related to a blown head gasket or a cracked engine. I'm open to any inputs y'all have.
I did the compression tests tonight. Here's what I came up with:
#1: 155 #2: 130 #3: 160 #4: 152 #5: 139 #6: 151
I also have pictures of the six brand new plugs. See below:
The plugs look rough for brand new plugs, don't they?
What does all of this tell me in terms of blown head gasket or cracked block/head? It overheated again Saturday night while idling in my garage, coolant boiling in the radiator again. Damn, this has been one helluva time trying to get this car back up to speed.
Plugs look like it's either running rich or maybe lean. If to lean it can not burn all the gas. But you mentioned it burning your eyes I think. I did a quick scan of the post. Didn't see unless I missed it. Have you ever checked the fuel pressure? That is one of the first things to do when trouble shooting.
Progress. I went to O'Reilly Auto and rented a fuel pressure test kit. I hooked it up to the Schrader valve, and checked pressure with the key in run, engine turned off. I started out with exactly 40 PSI:
Within less than two minutes, it was down to about 20 PSI:
I'm under the impression the fuel system should be able to hold pressure for significantly longer than a few seconds, and shouldn't be at half pressure in two minutes. I was not yet able to test the pressure while running because my plugs were still carbon fouled. I cleaned them and will put them back in tomorrow for a engine running pressure test.
Is the quick drop in pressure in run position with the engine off normal? If not, does this indicate the pump or pressure regulator is going bad?
Once the pump shuts off the pressure should hold for longer than 2 min. Can be regulator or could be leaking injectors. Looking at your plugs I'd guess the latter. But still would not explain why it dies once in closed loop. Did you watch the fuel pressure while running until it got to closed loop and see what happens?
Since my last post, I've verified that the fuel pressure stays well up into the 45 psi range after the car cuts off.
I've also had a master mechanic that works on government vehicles for a living come over to check on the Fiero. He quickly came to the conclusion that my catalytic converter was clogged. We separated the trunk-side exhaust header from the down pipe to confirm, and sure enough, the car pepped up.
Today, I removed the cat from the car. Imagine my surprise when I found this inside it:
That is one waterlogged, funked up cat! Here's how it looked inside:
I've replaced the cat with a test pipe for now to see how the car will respond. I have it in place, and I'm waiting for the 600 degree sealant to dry where I connected the test pipe with the exhaust clamps. Should be ready around noon or so. I will give it a go and will post again when I know how things work out.
Well, it seems like it might start running and stay running. I will need to set base timing again, and I really didn't get much time to look at the issue today. I was able to get it running and keep it running, but it's idling at almost 3k. I'm pretty sure this is a timing issue right now, so once I get that sorted, I'll update the thread again. No doubt of this though: the clogged cat being gone has helped already.
I still have work to do. It's still idling too high, and I'm still getting timing dialed in right. However, it is running and does not cut off until I turn it off. This is huge progress! It turns out, the clogged catalytic converter was pretty much the source of my woes.
So, after nearly a month, I believe this problem is solved. Thanks to everyone that has contributed to helping me get the car running again.