Car is a stock '88 Iroc 305 TPI with manual trans. Idles erratically and stalls when I try to take off most of the time. SES comes on after it runs for 5 to 20 seconds and stays on. I jump pins 5 and 6 and get code 12. That's it. It'll flash 12 for and hour if I let it. Anybody seen this before? I just want the ECM to point me in the right direction before I get the meter out and search the Haynes manual for procedures on checking every damned wire in the car. Any input is greatly appreciated. By the way I searched the forum for two and half hours and never found a solution for anything like this. I'm guessing it's "one of those" problems.

 

Have you started with mechanical condition, good compression. Correct ignition timing. this could be a bad iac, tps, plugs, wires. Injectors. Or even a bad ecm. You can Allways tap on the ecm case and see if it changes the running.

 

That was fast. Thanks! I have checked the obvious (my obvious, anyways.) Compression on all 8 cylinders was perfect. Base timing was dead on, 6 degrees BTDC. Plugs and wires passed the eye test anyways. They sparked bright. I did not install them; but the MAF is new and the TPS is new but I have yet to do .57 to 5v test with a meter to make sure it's good and adjusted properly. The IAC clicks in diag mode with engine off. The injectors all tick the same with a stethoscope on them but I need to ohm them. I didn't know about the ECM tap test so you've already helped. I'll do that and couple more things as soon as I get off work tomorrow and post my findings. Thanks again!!

 

I had limited time this afternoon. I started the car and tapped the on the ECM case and nothing changed that I was able to notice. I didn't let the car warm up very long though. I don't know if that matters or not. I also unplugged the MAF and TPS sensors and started the car and it ran much better if that tells anybody anything. I guess the next step is finding out how to test the ECM once I get a hold of a good meter.

 

Do you have a scanner to view the tps signal and the maf GPS ?

 

I do not have a laptop right now to pull any data from the ecm. I'm guessing I'm just shooting in the dark 'til I can find something to pull data with huh?

 

I'm really not sure what direction to point you in right now. Tuner pro rt is free, you will need the $6E definition adx file as well to connect. Connection needs to be made in 10k mode.

 

A little update... Laptop is still not fixed. I haven't had much time to mess with the car. I do have a couple of questions though. Can I pull useful data with car idling in the driveway? My driveway is on a the side of hill and I can go up and over the hill but whatever is going on with it causes it lose "drive-ability" and it's very hard to get her back sometimes. Next question is, will an OBD1 compatible handheld give me any useful data for solving this problem? Also, this is the most difficult vehicle that I've ever diagnosed. I've owned LS1s LT1s and several Vortec motors in trucks and a cheap scan tool and a meter was all I needed to figure out any problem. Am I alone with that opinion?

 

Since this is happening at idle yes you can get useful Information in the driveway. While warm log with tuner pro rt $6e adx.