PFF - Pennock's Fiero Forum, PDA Edition

87 GT died while cruising then finally came back to life (Page 1/3)

MattK

JUL 11, 09:50 PM

Hi all, recently I was cruising around in my 87 GT. Car was running great with no issues. After about 15 minutes of driving I noticed the voltage gauge hopping around momentarily. After a couple seconds it returned to normal. I continued driving about a mile down the road and suddenly my radio shut off. I quickly looked over and saw the voltage gauge and oil pressure gauge at zero, saw the CEL flash on and then immediately back off. My radio turned back on and gauges returned to normal. It happened so fast I didn't have time to register if the engine also died because it happened in a second. I immediately tried to pull off the road and park and just as I came up to an intersection 100 to 200 feet from where the first experience happened everything died again, engine included this time. At first I thought it was yet another failed ignition control module but I tried cranking the ignition and the engine actually turned over and revved up to 1000 rpm before dying after 1 second. I tried it again to the same affect. After about 10-15 attempts the engine turned over and remained running. I was able to drive through the intersection and into a gas station. There I topped off fuel since I knew I was lower but the tank only filled up 8 gallons (fuel gauge doesn't read correctly past half tank so I didn't know how low it was.) After filling up it started but when I put it in drive (auto) the rpms dropped lower than normal. After putting it back into park and letting it sit a minute I shifted back into drive with a much smoother transition. I proceeded to drive the car back home about 3 miles with no issues. Oil and voltage gauges were perfectly steady, engine ran smooth the whole way. When I got home I did check the battery and found the positive connector was about a quarter turn loose but that was it.

After having two ignition modules fail on me last year, resulting in needing the car towed to my mechanic, I'd be lying if I said I didn't get nervous every time I drive the car now. Of course now I know how to replace ICMs myself but the worry of breaking down on a busy road is always with me when I drive it, especially now with this new issue. I'm not all too mechanically savvy, but if anyone has any suggestions I'd be happy to hear it so I can do further research to see if it falls within my skill level to investigate further or not. I wasn't sure if it could be fuel filter or pump related. I believe those two were last replaced 15 years ago by my dad.

Patrick

JUL 11, 10:12 PM

quote

Originally posted by MattK:

I wasn't sure if it could be fuel filter or pump related. I believe those two were last replaced 15 years ago by my dad.

That's one of the easier things to check... with a fuel pressure tester.

I'd be more concerned with this...

quote

Originally posted by MattK:

After having two ignition modules fail on me last year...

And now it's potentially a third one that's failed within a year? To give some context, I installed the ICM that I'm currently using 14 years ago... and it was a used one to boot!

Are all the heat shields in place on and around the exhaust crossover pipe and EGR valve?

Did you put a very thin layer of thermal compound (not dielectric grease) between the ICM and the base of your distributor? If so, I suspect there's something else in your ignition system that causing your ICMs to fail, like maybe a bad pick up coil.

The Ogre should be by shortly to to give you links to his site regarding ignition components. [EDIT] Have a look at This recent ICM thread... Ogre's link is there.

[This message has been edited by Patrick (edited 07-11-2022).]

MattK

JUL 11, 11:45 PM

quote

Originally posted by Patrick:

And now it's potentially a third one that's failed within a year? To give some context, I installed the ICM that I'm currently using 14 years ago... and it was a used one to boot!

Are all the heat shields in place on and around the exhaust crossover pipe and EGR valve?

Did you put a very thin layer of thermal compound (not dielectric grease) between the ICM and the base of your distributor? If so, I suspect there's something else in your ignition system that causing your ICMs to fail, like maybe a bad pick up coil.

The Ogre should be by shortly to to give you links to his site regarding ignition components. [EDIT] Have a look at This recent ICM thread... Ogre's link is there.

Since this was my first experience with the ignition avidly turning over repeatedly I kind of ruled out the ICM. Last two times car died and had nothing left in the ignition. I read the thread you attached and yeah definitely not ruling it out anymore, though I agree something has to be killing these ICMs. Prior to these last 3 incidents over the course of 1 and a half years and less than 500 miles driven we never had any ICM issues and the car has been in the family for over 20 years.

I'm pretty sure all the shields are still intact around the exhaust. And yes I did apply a layer of thermal compound before installing the current AC Delco ICM. Sounds like it might be worth a shot to look further into pickup coils.

greenturnedblue

JUL 11, 11:58 PM

Any more detail about the voltage gauge jumping around? If the Alternator's voltage regulator is on the way out and the alternator is sending out erratic high/low voltage it could cause the ecm to go haywire and could lead to fried ICMs. The ECM will also shut off if voltage drops below 10v, which may explain losing power on the road

MattK

JUL 12, 12:04 AM

quote

Originally posted by greenturnedblue:

Any more detail about the voltage gauge jumping around? If the Alternator's voltage regulator is on the way out and the alternator is sending out erratic high/low voltage it could cause the ecm to go haywire and could lead to fried ICMs. The ECM will also shut off if voltage drops below 10v, which may explain losing power on the road

I have noticed that the voltage meter ticks back and forth between 12 and about 9 or 10. This usually happens either when I have the blinker on and it ticks with the blinker, or when my small subwoofer is on. But it will always only tick, like it's never more erratic than that. And it's been doing that for a very long time and never progressed worse.

MattK

JUL 12, 12:07 AM

quote

I can turn the car on tomorrow to try to get more precise readings for how far down the gauge drops. It might not be 9 or 10.

greenturnedblue

JUL 12, 01:54 AM

Let's just say the erratic voltage is the cause not a symptom. Too high voltage = fried ICMs and too low voltage = ECM shuts off. Seems to explain your issues? I would look into the alternator further and get it bench tested at an alternator shop. Is it still the original one?

theogre

JUL 12, 08:39 AM

⚠️ Warning: Iffy Alternator or Batteries can cause huge problems that can Burn a car down or you while working on them.
Don't drive the Car.

Don't trust volt and other dash gauges. Get a cheap meter to check volts across battery etc.

Iffy volts can make ECM to set "Codes" for High (53) or maybe Low Volts and flash or turn on MIL/CEL.
Also ECM can see weird volts and cause "Hunting Idle" or in case of low volts, High Idle sim to Vac Leaks.

Iffy Volts could be "bad" alt or several other things like side plug on the alt is bad or have crap wire(s) to it.
See my Cave, Alternator Sense for what the plug does...

Could have crap battery, bat cables or other wiring.
See my Cave, Wire Service

Check Battery. Charge the battery if under ~ 12.5v. But If < 11 volts battery is likely bad and Do Not charge. Take to auto part store Wmart etc for computer testing that test low battery for dead cell etc that can cause very dangerous problems if you try to charge.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

MattK

JUL 12, 04:06 PM

quote

Originally posted by theogre:

⚠️ Warning: Iffy Alternator or Batteries can cause huge problems that can Burn a car down or you while working on them.
Don't drive the Car.

Don't trust volt and other dash gauges. Get a cheap meter to check volts across battery etc.

Iffy volts can make ECM to set "Codes" for High (53) or maybe Low Volts and flash or turn on MIL/CEL.
Also ECM can see weird volts and cause "Hunting Idle" or in case of low volts, High Idle sim to Vac Leaks.

Iffy Volts could be "bad" alt or several other things like side plug on the alt is bad or have crap wire(s) to it.
See my Cave, Alternator Sense for what the plug does...

Could have crap battery, bat cables or other wiring.
See my Cave, Wire Service

Check Battery. Charge the battery if under ~ 12.5v. But If < 11 volts battery is likely bad and Do Not charge. Take to auto part store Wmart etc for computer testing that test low battery for dead cell etc that can cause very dangerous problems if you try to charge.

MattK

JUL 12, 04:07 PM

quote

That's a lot of helpful info. I'll definitely look into the battery and alternator and find out from my dad when either were replaced last when he was still driving it.