Hi!

I have a 91 Z28 305 Auto that doesn't like to stay running. Today I replaced the Coil/Cap/Rotor/Wires/Ignition Module with all new ACDelco parts. Problem/symptoms remain the same.

Car will idle all day long but when you try and drive it (or rev it) it just dies. No mis-fire, no sputtering. Just dead. After it dies you can start it back up and repeat the whole process. Was really thinking it was the ICM so I'm pretty bummed that didnt fix it. Could it be the ECM?

I believe this problem has gotten progressively worse. A few months ago the car used to run like a top and then randomly have this horrible misfire. You could keep your foot in the gas and it would stay running, but it would sound like a top fuel dragster idling. And then just as quickly as the problem started, it would run fine again.

This current problem seemed to start after I took the car on a "spirited" drive on the highway to dry it off I kept my foot in it until I hit about 110 (which takes awhile in this car) and thats when it first died. It felt like the speed limiter kicked in, but it never recovered. After about 5 seconds of it coasting it started to pull again. 5 seconds later it died. 5 seconds later it pulled. It did this about 5 times before I made it to the next exit ramp. It just got worse and worse. Eventually I limped the car home at about 20 mph trying to keep the RPMs under 2k.

Fuel pressure seems fine.

You will see a SES code in the video. The only code I can pull is "15" which I believe is "Low engine temp reported to ECM" or something. Related?


(View Of Tach)

(Different Video. View of fuel pressure gauge)

 

UPDATE :

Fixed the SES (Code 15). The connector for the coolant temp sensor was corroded. SES light no longer comes on while the engine is running, but it still runs/dies just the same.

Side question : How do you remove stored codes from the ECM? I removed the ECM fuse for about 30 seconds, but that didn't seem to do it.

 

If the original factory Multec injectors are still in the engine, replace them.

As for the code, find the inline fuse that is under the hood and pull it out for at least 10 minutes. Or wait for 50 start ups with no further malfunction codes and the ECM will erase the code(s).

RBob.

 

Thanks for the reply. I'm not sure if they are original. Is there a way to tell without pulling them? If I do have a bad injector could it fail in such a way that it effects all the other injectors?

 

The Multec injectors fail by the coil shorting out. Once there is enough of them with the coils shorting none of the injectors get fired. There is only one driver in the ECM for the injectors.

Multec injectors have a smooth straight body that are two tone in color.

RBob.

 

RBob,
You are the man!! You hit the nail right on the head the first time

Injector #2 is the culprit. Before testing the injectors I did a test to see if the car was losing spark or fuel when it died. Judging from the video it's pretty clear it's still getting spark so that ruled out pretty much all the ignition stuff :

Running on 7 cylinders

Based on RBob's suggestion of a bad fuel injector, I started pulling the connectors off one injector at a time. 1, 3, 5, 7, 8, 6, 4 and wouldn't you know the last one I pulled (2) was the bad one. Car ran on 7 cylinders but I could not get it to die. Plugged injector 2 back in and it failed quickly after.

Injector #2 test

I just want to say thanks so much for saving me a lot of time swapping parts. The ECM was going to be next.

 

Ok I'm having the same problem when it runs fine but when I drink e it a lil it wants to stall out every time I give it gas blows black smoke and iv tryed everything really needing some help before I blow the Damn thing up replaced the air idle control sensor and all still nothing help

 

And I have a 86 350 tpi