Hello,

I have a 1987 trans am gta 350 TPI. The motor is only about 4 years old. When I did the swap I replaced countless parts along the way, keeping things stock other than headers and getting rid of the egr valve and smog pump. I have put a couple thousand miles on the new motor.

Starting last year, the car would randomly shut off while I was driving to work. It didn't spit and sputter or act up first, just shut off. my radio and dash lights all stay on. Once I coast to a stop, I put it in park and the car fires back up like nothing ever happened. I would make it to work and back home without a repeat problem.

This has happened a hand full of times. The other night, it shut off twice in about a 5 minute period while moving stuff around in the shop. Once while idling in park, and once when I starting moving in drive.

Parts that I replaced in the last couple years include injectors, fuel pump, fuel filter, fuel pressure regulator, distributor asm (not including the coil), plugs and wires, ecm and prom, coolant sensors, oil pressure sensor and sending unit, fuel pump relay, maf relay and the 3rd relay which I can't think of. The maf itself and probably more I haven't listed.

If anyone has any suggestions please let me know!
P.S. the parts listed above were all done previous to this problem I'm having. Thanks in advance!
Nick

 

Only on initial start up I had a intermittent start and after about 5 seconds engine would die that took forever to diagnose and fix but it turned out to be the wiring/pigtail for the fuel pump relay was bad and after replacing it no more intermittent start and die. I would check your wiring there and on the ground on the back of the heads.

I only found the wiring issue as I was lucky enough to have live data hooked up at the time, if not I would likely still be chasing my tail. A scanner tool is really needed for these cars to help diagnose.

 

Thanks I will check that.

What kind of scanner tool do you recommend for in depth obd1?

 

You can't go wrong with the old Snap On MT2500 or the brick as it was known but they are older now and not exactly inexpensive and you need to be sure you have the right keys for your car.

I actually use the 1320 electronics Bluetooth scan tool which was recommended to me by another member. You need an old Android phone and other than that I picked up a cigarette lighter type power adapter to connect to the car's battery terminals to power it. I can't remember the app I used to but I want to say it was ALDL Droid. It has proven to be very handy when working on my car and for around $100 all in I am happy. The initial set up is a bit tricky, basically selecting your year/engine set up etc, but I'm also not a huge tech person and I got it to work.

Here is the link:

http://www.1320electronics.com/12pin_ALDL_BT_MK2.html

 

I went to the website and unfortunately they are all out of stock. I hope they didn't quick making them. Maybe I will search for an old snap on brick.

Also, my car doesn't typically set a check engine code when it shuts off. It just immediately fires back up and may not repeat for a day or so.
Thank you

 

Mine never threw a code either, I actually caught it when I reviewed the recorded live steam and saw an anomaly when the fuel pump voltage dipped and the car stalled out.

That’s unfortunate he’s been out of stock since COVID likely because of the chip shortage. There are plenty of the snap ons on eBay.

 

Do you happen to know, or have a diagram on where all the grounds are in the engine bay? I've felt on the back of the head, and they all feel tight. I just want to make sure I'm checking them all.

I will double check my pigtails tonight, but when I did the fuel pump relay, the maf power and maf burn off relays, I also replaced the pigtails for each one becuause I didn't like how sloppy the original ones were.

The time it shut off the other night, I was going slow enough that I heard the fuel pump do its little 3 second prime cycle like I had just turned the key back on.

The other weird thing that happens, is sometimes when I'm inside the car, and the key is in accessory, my radiator fans will come on sometimes. And I don't think they should unless it's running or at operating temp. Please correct me if I'm wrong.

I've replaced so many things that people suggest could be issues, that it makes me wonder if I have a ground issue somewhere.

 

[QUOTE=nickalope24;6502694]Do you happen to know, or have a diagram on where all the grounds are in the engine bay? I've felt on the back of the head, and they all feel tight. I just want to make sure I'm checking them all.

I will double check my pigtails tonight, but when I did the fuel pump relay, the maf power and maf burn off relays, I also replaced the pigtails for each one becuause I didn't like how sloppy the original ones were.

The time it shut off the other night, I was going slow enough that I heard the fuel pump do its little 3 second prime cycle like I had just turned the key back on.

The other weird thing that happens, is sometimes when I'm inside the car, and the key is in accessory, my radiator fans will come on sometimes. And I don't think they should unless it's running or at operating temp. Please correct me if I'm wrong.

I've replaced so many things that people suggest could be issues, that it makes me wonder if I have a ground issue somewhere.[/QUOTE

Something is up with your electrical system or ECM it seems to me, I don’t think the fan should come on unless temp is high enough, AC on, or you are in diagnostic mode (a paper clip in the 2 ports for the ECM or scan tool).

Here is a quick thing to try, make a paper clip into a U shape and place each end it in the final 2 on the top right. Once the clip ends are inserted turn the key to on position. The check engine light will flash 12, as in one flash, pause then 2 flashes three times to let you know ECM is functioning and connected. Any codes stored will show after 12.



Use the top picture for reference.


Have you checked your connections at the ECM? Next I would wonder if the ECM is the problem but I wouldn’t want to just keep throwing parts at it.
Without live data I would try to find a shop that knows OBD1 cars and have them look to at least diagnose but finding anyone who knows these cars is getting tough, I’m lucky I have a shop local that can do that.

 

The fans coming on occasionally with koeo sounds like a faulty ecm or memcal not seated properly.

 

Yeah something weird has been going on basically since the new motor. I had a really choppy idle, like it had a fat cam in it that I was chasing for like 2 years. It drove perfect but idled terribly. I don't think it ever died on me though.

The ecm was one of the many parts I threw at it trying to fix my idle.

The idle issue ended up being the prom, or memcal. I replaced it in February 2022 and it's idled great since. But that's also when I believe my intermittent shut off issue started. I was pretty sure the memcal was seated properly but maybe I need to get back in there and recheck it and the connection going to the ecm.

The only other time the car died was a couple years ago it shut off on me on the highway, then I was able to fire it back up, and I had thought it was the fuel pump, so I replaced it. Then the car didn't die until last summer.

Do you think I could have a faulty memcal? That's the last thing I did to it before I noticed this issue.

Thank you guys for responding so promptly. You don't know how much I appreciate it!

 

Memcals rarely go bad, when they do you get a rapid blinking check engine light.
or you might get a code 41 or 51 .

 

UPDATE

I ended up getting a replacement memcal, and while I was in the dash, I used dielectric grease on the new memcal, the ecm plugs and every single other connection I could find in that area.

I also took down the lower dash panel on the driver's side under the steering wheel and the kick panel. I aplied dielectric grease to every plug there as well. Including the plugs on the bottom of the steering column I believe to be for the ignition.

I'm not sure if it was one of the connections, or the memcal, or a combination but this was done last Sunday and I was able to drive the car to work a couple times this week, and let it idle for probably over an hour throughout the week, and so far I haven't had any sort of issues!

Just thought I'd share my findings. Hopefully this can help somebody else if they are experiencing a similar issue.

Now on to figure out my code 36 for the maf system haha. Thanks for all the helpful comments.