Hey all,

Brand new here. I just bought my 1988 IROC Z 350 TPI a few weeks ago. 57k miles, excellent condition. Since I've had it, I've had these seemingly random issues with starting and idling, where the engine will crank and die almost immediately, and the SES will light up. If I continue trying to start it up, eventually it will stay running, but it'll idle very high, around 1500 rpm. When I put any strain on the engine at all, like putting the AC on, or putting it in gear or giving it gas, the engine will bog down and eventually stall. Once it warms, the symptoms tend to lessen. Sometimes the car will "correct" itself and the light will go off and the idle will immediately return to normal, around 700, and it drives fine, but sometimes it doesn't. Often the behavior isn't present at all, and it'll start right up and drive like nothing is wrong, no SES light, and it'll drive like a champ for miles, and then sometimes when I go to start it the next day after driving it, the same behavior will happen out of nowhere. There also seems to be a faint burning smell coming from the car when running.

Any help would be really appreciated as it's driving me nuts. Seems to happen at random. I've had two mechanics look at it and so far we've replaced the fuel filter, IAC, distributor cap and rotor, and I cleaned the MAF with MAF cleaner. Nothing seems to have solved it. The next thing I'm trying is the ignition control module, but I'm not sure this is going to solve the problem. It seems like it's an engine control problem with the ignition system, like a sensor, relay or something with the ECM due to it's seemingly random nature, but I'm not sure.

Thanks in advance for any input! I'm running out of ideas and don't just want to keep replacing things and spending tons of money without solving the problem.

 

Have you checked the code(s) from the SES light?

 

I had a similar issue with my bird several years ago. Bad ECM. Got a re manufactured one, pulled the chip out of the original, swapped it and never an issue since.

 

I will second Hawkeye on this, my 88’ GTA had an intermittent stall only at cold start up. It wasn’t every time but at least almost every other time I started it cold. On a chance I found a new AC delco ECM on eBay and installed it and it hasn’t happened since. I read an old hot rod article about how these ECMs are prone to failure and doesn’t seem rare for them to die. Also had a MAF that would heat soak and cause all kinds of issues, the MAF is very important and sensitive on these cars. They also seem to work best with Bosch maf sensors and aftermarket ones can cause fits.

However, if you want to be sure get some live data when this is happening and that should help you a lot. You can get into a Bluetooth style ALDL adapter that pairs with an old android phone/tablet with aldldroid or aldl scan app and have live data for under a $100.

 

Thank you sir for your input!

I will tell you the cheap way I tested my bad ECM. My car would start but run horrible and drive like yours did when the check engine light came on. I was told, take the ECM and put it on the passenger side seat. Leave it plugged in. Get the car running right, no light, idle good, running good. Then wrap on the ECM with your knuckle hand as a fist., knock on it like you would a front door to a house. If the engine light comes on and the problems start as you stated. Bad ECM.

 

Thanks everyone for your input. To answer TTOP350, I haven't been able to get a code out of it. I tried the paperclip trick in the ALDL connector, and the light just stays solid. Tried a few different paperclips and was not able to get it to blink the codes. I've been suspecting a bad ECM but wasn't sure. Do the ECM's need programming in these cars? Cause I would have no idea how to do that lol.

 

When you put the paper clip into the right spot , top right and the one next to it (AB connector) you should hear the fans kick on and then flash code 12 three times which means the ECM is working and in diagnostic mode. Sounds like a bad ECM or wiring to it.

No reprogram if you get a new one, all you need to do is carefully remove the PROM chip from the old one and transfer to the new one.

 

Lack of ecm communication is a sign of a bad ecm. Do you have a scanner or datalog cable to confirm?

 

You need one that matches your car. As I recall I had to give my VIN number to the seller. They aren't as sophisticated as the ECM/PCM are today.

 

It’s a 1227165 service number or superseded same for 86-89 Tpi

 

So update: I bought a reman ECM from Cardone and I swapped it out and transferred the PROM, and now I’m able to get code 12 out of the ALDL and so far no issues. So fingers crossed! I want to put a decent amount of miles on it before I can confirm it’s fixed.