GREMLIN CONTINUES TO BE PRESENT MAKING DRIVING UNSAFE

[Hunter Dog]

My 87 GN which I bought in 87 continues to have a gremlin that seems impossible to find. The car is not a modified car, is stock and has 115,000 miles on it. It is a show car and has been garage kept and basically been babied it's entire life. It is only driven to car shows and out for a short drive here and there. I am the one and only owner of this car. It has never been wrecked but will be in an accident if we do not find the issue at hand which is very scary.

Starting about 6 to 8 years ago and out of nowhere the car simply died when driving home from a local car show. This continues to happen on average of maybe two times per calendar year. I put an average of 2,500 miles a year on it over the last ten years. The car has never done this upon acceleration, only when braking or turning.. I have gone over every case and this is the only pattern we can find.

The car has quit in 70 degree and 90 degree weather and when the car has been driven 15 minutes or over an hour on a longer trip. It has quit at a stop light or simply making a normal turn. It has quit under normal breaking or hard braking with no turning involved.

At the first local car show of the year last week it quit on the way home under normal breaking conditions and this was the first time in almost a year it has done it. What took place this time was the service engine soon light and several lights on the left side all came on at the same time before I realized the car was not running. I was in heavy traffic and was lucky no one was in the right lane so I was able to get in the right lane and coast off the road. I have no power brakes or power steering when this happens. Because of the heavy traffic I was not able to look closely at the lights on the left side to see which one(s) were on.

We have been very, very close to being rear ended on a highway several times. Each time when I have been lucky enough to pull off the road, the car has started back up every time after several minutes. Sometimes I have to try several times. It seems the longer I sit there, the more likely it is to start. I have never been completely stranded and I think the longest it has taken to restart is maybe 15 -20 minutes.

I do own a powerlogger and my thinking is I need to have it recording all the time every time I drive it to see if the incident will occur and see if it picks up anything. I also now own a BlueDriver scan tool that I have been using on some other family vehicles with some good results so I am thinking of keeping this with me and plugging that in right away the next time it happens.

Over the last five years I have changed the ignition module/coil pack several times thinking maybe that was it, but over three of them it continues. I have put in a new battery every 3-4 years, an AC Delco each time. This car runs on 93 octane. It has the original motor and wiring harness and ecm. This problem never happened prior to 2016 or 2017.

Please give this some thought and thank you in advance for your opinions. I hope no one else is experiencing this kind of thing but if perhaps someone did in the past 35 years and they found the smoking gun I would appreciate this feedback as to where to look.

 

[1986 Buick GX1]

It almost sounds like the braking are the common denominator.
Does it have the factory power master brake system or has it been converted to vacuum brakes?

 

[Hunter Dog]

Converted to vacuum brakes around 2010 well before the issue started. Anything is possible. I would add that my foot is not always on the brake when this has happened..I can just say for sure I have not been accelerating.

 

[turbohh]

I had a similar issue once a while ago in my 87 GN ... Car died while driving on the highway ... It turned out I had an intermittent open in one of the fusible links in the wiring down by the starter ... I think when this happened I had no power to anything though. But there are two or three of the fusible links in the harness going to the starter, so some may be more important than others ... They are prone to being glitchy as they get old and heat-embrittled ... Just a thought to consider ...
John A

 

[Ktbregal]

Have you pulled the ecm out and tapped on it while driving or sitting?

 

[dynoman]

I had an issue with my car very similar to yours , where the car would shut off for no apparent reason while driving . I first noticed it at the track as a very quick loss of a Powerlogger log , just a blip of no data . It later morphed into shutting off completely . It turned out to be a bad wiring harness connection to the ECU and I ended up replacing the 2 connectors with Caspers pigtails .
I would check the ECU connectors , unplug them , check for corrosion and spray with contact cleaner and if that doesn't work replace them .

 

[scgnx2]

Use your scan tool and post the numbers at warm idle. MAF, BLM, INT, BAT, etc. A Powelogger file would be very helpful otherwise it’s a guessing game.

 

[John Larkin]

Try to tighten the harmonic balancer. This happened to me several times years ago. It walks forward and loses contact with the crank sensor. Clamp some vice grips really tight on the flywheel, then get a torque wrench and tighten the balancer, I think it is 235 lb ft but double check the spec first. It fixed my problem.

 

[TireFryer]

When mine would die it turned out to be a worn can sensor along with a cheap sensor cap. I’d check that and the crank sensor.

 

[salvageV6]

Look for this connector behind the glove box covered in gray foam. Pink wire you see I bypassed the connector with a splice provides power to the ECM.
That's where my intermittent car dying while driving problem was.
All I had to do was idle the car in the driveway and wiggle each wire at each end and easily found that was the issue as it died every time.
Took about 2 years to find it on a daily driver.

 

[WE2Regal]

I had a GN with an intermittant stalling problem after driving a while that turned out to be a bad fuel pump relay. It would shut off like you turned the key off with no sputtering. Once it stalled, it would take several minutes to refire (I assume because the relay had to cool down). You need to pull over and have somebody crank the engine and determine if you have a spark or fuel issue. I knew it was easy enough to test for spark by removing a plug wire. I had a fuel pressure gauge hooked up and never lost fuel pressure. I finally bought a noid light and removed an injector clip so I could quickly pull over and plug it into that injector wire. Sure enough, no injector pulse. Had to study a wiring diagram to see why.

 

[Hunter Dog]

Have you pulled the ecm out and tapped on it while driving or sitting?

No. Do you mean in an effort to see if the car shuts down? I could probably try this on a country road with no traffic to see. May be worth a try. Thank you for your reply, much appreciated.

 

[Hunter Dog]

Look for this connector behind the glove box covered in gray foam. Pink wire you see I bypassed the connector with a splice provides power to the ECM.
That's where my intermittent car dying while driving problem was.
All I had to do was idle the car in the driveway and wiggle each wire at each end and easily found that was the issue as it died every time.
Took about 2 years to find it on a daily driver.
View attachment 398713

I can do this at home vs trying something while driving it. I am watching all the replies (thank you by the way) to see the list and start going down the list with easiest to hardest to do if I have not already tried it. I have not looked at what you are suggesting on this car although we did look in this part of the car on an old Firebird we had as the radio kept going out and we found it the same way as it was the wires on the way to the BCM in that case. Thank you for your reply. Much appreciated.

 

[THensley]

Post #10 that pink wire is key. Your first and free ,place to start ,sitting in the driveway its time to give all key connection the wiggle test.
ECU plug ,fusible link ,Pink wire behind the glove box the purple wire over buy the break booster.
Its ugly and not really ideal but a fuel pressure gage stock under the wiper just to confer fuel pressure when it dose happen

 

[Hunter Dog]

Post #10 that pink wire is key. Your first and free ,place to start ,sitting in the driveway its time to give all key connection the wiggle test.
ECU plug ,fusible link ,Pink wire behind the glove box the purple wire over buy the break booster.
Its ugly and not really ideal but a fuel pressure gage stock under the wiper just to confer fuel pressure when it dose happen

Thank you very much for the post. I will keep this along with the notes and other comments and start the process. Like you said, this one is the safest to do while in the driveway and no cost, only labor so glad there is something we can try like this right off the bat.

 

[MikeS]

In line with post #10- trace the ecm power wire from the battery along the inner fender and wiggle it around with the car idling in the driveway. My intermittent “car shuts off for no reason” ended up being a break in this wire, which was still held together by the wire covering. I caught it by chance as it arc’ed while I was staring at the engine.