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.

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).]

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.

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

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.

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?

⚠️ 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

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.

There appears to be a lot of focus on the voltage fluctuation causing the stall. I suspect it's possibly the other way around... the engine stall is causing the voltage fluctuations.

When an engine stalls, the needle on the voltage gauge is going to move... and in the excitement of it all, it's probably pretty easy to not be be observing exactly (and/or correctly) what's going on with the voltage gauge needle in relation to the stalling engine.

Everything turned off?! Maybe the ignition switch has moved out of it's proper position?

Radio and gauges shutting off indicates a powersupply issue, either alternator/batt or a bad (ground) connection. Is there a difference in behaviour when the car is warmed up or cold?

quote Originally posted by MattK: After about 10-15 attempts the engine turned over and remained running.

What does that actually mean?

An engine "turning over"... is simply an engine being turned over by the starter. It doesn't mean the engine is starting/running.

So when you stated "After about 10-15 attempts the engine turned over", are you saying that you turned the key to the Start position 10-15 times and nothing initially happened... or that the engine turned over but wouldn't start?

quote Originally posted by Patrick: There appears to be a lot of focus on the voltage fluctuation causing the stall. I suspect it's possibly the other way around... the engine stall is causing the voltage fluctuations. When an engine stalls, the needle on the voltage gauge is going to move... and in the excitement of it all, it's probably pretty easy to not be be observing exactly (and/or correctly) what's going on with the voltage gauge needle in relation to the stalling engine.

Engine Stalling will not make Volts Meter to drop to 9 to 10 volts as MattK claimed.

Stall shuts off the Alternator and dash gauge should read 12 to 13v for a charge battery allowing some dash gauge problems.

This is why you check the alt and rest of wiring First.
Then check ICM or whatever that can "go nuke" and not start when hot.

quote Originally posted by theogre: Engine Stalling will not make Volts Meter to drop to 9 to 10 volts as MattK claimed. Stall shuts off the Alternator and dash gauge should read 12 to 13v for a charge battery allowing some dash gauge problems.

I don't disagree.

quote Originally posted by Patrick: When an engine stalls, the needle on the voltage gauge is going to move... and in the excitement of it all, it's probably pretty easy to not be be observing exactly (and/or correctly) what's going on with the voltage gauge needle in relation to the stalling engine.

I had a total charging failure while I was driving my Formula home in May of last last year. I initially noticed the glowing red charging light, and then I noticed the reduced voltage (from 14 to 12)... and then I noticed the voltage was getting lower as I continued to drive. At first I thought the belt must've broken, but it was fine. I made it home, immediately ordered a replacement CS alternator... and then discovered the next time I started the engine (after charging the battery)... that the old alternator was charging fine... and continues to do so 14 months later. I can't explain what happened there. However, I have a nice newly re-manufactured 105 amp ACDelco alternator sitting here in its box should the need arise.

[This message has been edited by Patrick (edited 07-12-2022).]

quote Originally posted by Patrick: I had a total charging failure while I was driving my Formula home in May of last last year. I initially noticed the glowing red charging light, and then I noticed the reduced voltage (from 14 to 12)... and then I noticed the voltage was getting lower as I continued to drive. At first I thought the belt must've broken, but it was fine. I made it home, immediately ordered a replacement CS alternator... and then discovered the next time I started the engine (after charging the battery)... that the old alternator was charging fine... and continues to do so 14 months later. I can't explain what happened there. However, I have a nice newly re-manufactured 105 amp ACDelco alternator sitting here in its box should the need arise.

That isn't = to a stalled engine.
When alt is off/dead for any reason and you keep driving then Battery will get lower and lower then die too.

When the battery dies depend how much power car uses, condition of battery, and in US a spec call Reserve Time. (Cave, Battery)
If drive at night then have HL and other lights draining the battery vs day time when engine is main load. AC On then add that load to either sucking down the battery.
Cheap battery often have a lot less RT vs good Wet or AGM batteries. But caution, While longer RT is good on paper you don't what to push the spec because every time a starting battery is < 11.7v can shorten the lifetime at minimum. But having a good battery w/ long RT Is good when your on limited access road and maybe drive to next exit or home anywhere near there to avoid a tow bill.

But That's ignoring 12SI Alt he should have like to barf up a Diode Trio and when true that can kill the battery by itself. (Only 87-88 L4 and 88 V6 Fiero have factory installed CS130.) If any SI is "dead," get to a safe spot to park fast and disconnect the battery in case the alt is draining because that try to drain the battery to 0volt and destroy a good battery. Iffy Gen 1 HL motors and some others can do same w/ I-key Off.

quote Originally posted by Patrick: ...the old alternator was charging fine... and continues to do so 14 months later. I can't explain what happened there.

Okay, this is really weird. I posted a few hours ago that my alternator has been working fine the last 14 months after a single episode of the alternator not charging. Two hours after I posted that, I got in my Formula, turned the key, the engine snapped to life... but the charging light was glowing red and the alternator wasn't charging. Wow, talk about jinxing oneself!

Obviously, I did not continue on my way in the Formula. That is really really weird.

Check the connections and wires themselves, at the terminal strip next to the battery, under the C500 connector. That's the power distribution point for the entire car.
There is one wire that feeds, essentially, the entire front half of the car (including the fuse box). If that wire breaks - or the fusible link at the terminal burns out - it will make everything blank out. Lights, radio, engine, everything.
My car had a bad splice, and did exactly what you described - including everything going out, while going down the road. Since the connection was intermittent, it recovered, and then died again.

quote Originally posted by Patrick: Okay, this is really weird. I posted a few hours ago that my alternator has been working fine the last 14 months after a single episode of the alternator not charging. Two hours after I posted that, I got in my Formula, turned the key, the engine snapped to life... but the charging light was glowing red and the alternator wasn't charging. ...That is really really weird.

[This message has been edited by Raydar (edited 07-13-2022).]

quote Originally posted by Raydar: Aliens.

I agree. That's the only explanation that makes sense.

quote Originally posted by Patrick: Okay, this is really weird. I posted a few hours ago that my alternator has been working fine the last 14 months after a single episode of the alternator not charging. Two hours after I posted that, I got in my Formula, turned the key, the engine snapped to life... but the charging light was glowing red and the alternator wasn't charging. Wow, talk about jinxing oneself! Obviously, I did not continue on my way in the Formula. That is really really weird.

hi Patrick, Intermittent charging from your alternator may be worn brushes sticking in their holder. With your skills, you might want to attempt repairing the alternator yourself, checking the bearings and replacing the brushes, before surrendering it as a core?

quote Originally posted by Rexgirl: Intermittent charging from your alternator may be worn brushes sticking in their holder.

That's exactly what I suspected when it first occurred (and started working again) 14 months ago. It's the only plausible explanation... well, other than aliens.

I have my Subie to drive until I rectify the situation, but I thought I might first just "gently" tap the alternator to see if I can persuade the brushes to un-stick again. If worse comes to worse, I have the new alternator sitting here that I bought last year.

[This message has been edited by Patrick (edited 07-13-2022).]

<X>The Truth Is Out There<X>

Edit - I used to have an 88 Firebird. Used essentially the same alternator.
It had a bad connection on the PC board, somewhere near where the connector plugged in. You could flex it, and then it would charge, and then it wouldn't.
This was before I had the knowledge/nerve to dive into an alternator and resolder connections.

[This message has been edited by Raydar (edited 07-13-2022).]

quote Originally posted by Patrick: What does that actually mean? An engine "turning over"... is simply an engine being turned over by the starter. It doesn't mean the engine is starting/running. So when you stated "After about 10-15 attempts the engine turned over", are you saying that you turned the key to the Start position 10-15 times and nothing initially happened... or that the engine turned over but wouldn't start?

The engine would turn on, rpms would reach 1000rpm and it would shut off again after about a second. I turned the key right after it died and again the engine would turn on, reach 1000 rpm and shut off after about a second. I did that about 10 -15 times until finally the engine stayed on and I drove off the street into a parking lot.

3-4 year battery can have problems more so if not driving to charge it often. Few days or months old battery can have same problems...
Lead Battery for starting a car work in a Narrow Window of Volts. run under < ~ 11.8 then life drops. way under life like < 10v drops Very fast.

Other batteries are similar. LiIon only last when operate 3 ish to 4.1 or 4.2 depend on how made. And these Hate Trickle Charge and other schemes Lead, NiCD, and NiMH uses to charge that can cause fires or worse on LiIon..

Alt gets nothing, runs 14month then nothing can be iffy side plug or anything internal. Dash light On then at least lamp works and side plug is good for L pin for CS. (B pin for all SI units.)

I've read about - and have experienced - secondary voltage loss. You can see evidence of this when your car is idling. Watch the RPM gauge. Will it suddenly jump, either lower or higher? It won't jump much.

When it's dark, open the deck lid, turn on the car, and watch. You may see occasional blue sparks from the wires. It causes the electrical system to work harder to compensate, frying your ICM over time.

The age of the wires is irrelevant - mine were brand new out of the box and there was a fairly regular jump from the wire to the engine block. Some dielectric grease solved that specific issue.

Ignition coils that have started to break down can also cause this. They'll be fine cold but once things warm up, not so much.

quote Originally posted by MattK: The engine would turn on, rpms would reach 1000rpm and it would shut off again after about a second. I turned the key right after it died and again the engine would turn on, reach 1000 rpm and shut off after about a second. I did that about 10 -15 times until finally the engine stayed on and I drove off the street into a parking lot.

As I mentioned way back Here, I still think you should check the fuel pressure... and if nothing else, at least eliminate one variable.

[This message has been edited by Patrick (edited 07-15-2022).]

We never did hear whether or not MattK resolved his issues... but my alternator mystery continues. Two months ago my Formula's alternator "healed" itself after not charging and it's been fine ever since, but today the same nonsense occurred again. I was almost home, and the charge warning light came on. When I pulled up beside my house, I left the engine running, and opened up the decklid so that I could tap the alternator (trying to dislodge potentially stuck brushes). Nothing happened, Charge warning light remained on. If there's no second miracle "recovery" overnight, I'll install the new alternator that's been sitting here for a year and a half. I'll then also take the old alternator apart to see if the brushes are indeed sticking.