I have a 1994 z28 automatic transmission camaro with the dreaded Stalling issue. I was hoping to get some feedback from someone that can translate Scan9495 logs (version 2.6.2). I want to start out by saying that I rarely drive the car, I have owned it for about 3 years. I drove a few times in the past month and I noticed it was starting to surge when driving the car, i didn't notice any surge in idle. About two weeks ago, it stalled on me and now as soon as it seems to warm up, it stalls. I went ahead and did the Cooling mod to the ICM and Coil, but it still stalled, I then decided to replace the ICM with a new ACDelco one from Rockauto but it continues to stall as soon as it warms up. From everything I am reading, most comments point to the dreaded Optispark. The water pump doesn't appear to be leaking any fluid and I am not losing any coolant.

The log file attached includes me starting the car in park for 4 minutes and then going on a 8 minute drive and captures it stalling while driving. The car wouldn't start right back up but did within 5 minutes and ran awful for the last 2 miles to get it home. I wasn't able to capture that part in the log. If there is anything else you need me to provide, let me know and I will be happy to do so.

 

I downloaded the file and started setting it up.

I edited (bold) your post to insure I picked up the problem you are trying to solve. When during the "warming up" did it stall? I scrolled through 3,350 lines of data, and the RPM never dropped below 765 from the time you started the engine.

Is the engine and PCM program totally stock? If not, what modifications have been made to the engine, and who tuned it for those changes?

 

Thanks for looking at the attached log and trying to figure this out. As far as I know, the car is completely stock, it even has the original style rectangular tailpipes. I see no modifications to the engine at all. I am not sure if it was ever retuned but from the looks of it, no mods were ever made. It even had the original tape deck.

It seems to stall soon after it warms up. I started the car and let it run for 4 minutes and then was going on a 10 minute drive, 8 minutes into the drive is when it stalled. It wouldn't start back up right away, But after a few minutes, I was able to get it started and drive it back home, So when the data stream stops is when it stalled out and shut down.

I have been able to drive it for a short 2 mile drive and back and then while leaving the car run in park after a few minutes it will just shut off. Sometimes it starts back up, sometimes not.

 

I don't want to jinx this..... but I have witnessed several instances of the Opti-spark failing upon warmup. As it gets warmer, the internal parts expand and connections between them fail if they are not secure. Hope I am wrong. Fred is usually right.

 

I just realized I have 5 different people I'm simultaneously trying to help (4 here, 1 on another LT1 site) with data logs at the same time. Please be patient if I don't get back to you right away. These can be very time consuming.

 

absolutely, no problem. I appreciate you taking a look.

 

Actually, yours seems to be straight forward. Mainly need to look at the frame before and after it shut off. Unfortunately, the cause is not clear.

Everything is going along fine for 12.6 minutes, and yep... instantaneous shutoff. Possible causes:

- PCM continues to function, but some data fields go to "0". I don't know if there was a total loss of switched ignition power to the PCM, whether some parts of the PCM continue to function on the direct ("PCM BAT") power from the battery. GaryDoug has a complete LT1 simulator setup, with the PCM, Opti, sensors, etc. I'll ask if he can determine what happens when there is a loss of ignition power, but PCM BAT power holds. When it stalled, did you try to restart, and did the normal dash light check occur when you turned the key to "run"?

- Loss of fuel. In the last frame where the engine was still running, both left and right O2 sensors drop to 0.004 volts. Fuel pump can be subject to heat soak issues. Injector pulse width is still shown as 6+ milliseconds after the O2 sensor volts drop.

- The Opti is always a suspect. RPM drops to "0" immediately. RPM comes from the low resolution signal from the Opti optical cam position sensor. Loss of low res pulse shuts off the fuel system. Could explain O2 volts dropping, and the injector pulse width in the "stall" frame is "0"

Doesn't really clear the problem up.... but maybe points to some things to look at. Immediately after the engine stalls you need to watch the dash for signs of loss of switched ignition power, check the fuel pressure while it still won't start, check for Opti signals (does the tach move up ~200 RPM when the engine is cranking?, check voltage on white wire to ICM with engine cranking).

 

Thanks for the info! I was able to replicate the stalling tonight by just letting the car run in park for about 10-15 minutes. I linked to a video of it stalling and what is displayed on the dash, I did notice after it stalls the battery level gets really low.

 

For anyone interested, I was able to resolve the issue by replacing the Opti.