Hey all, I'm helping a neighbor with a 93 corsica 3.1l v6. I only know about older vw's (bosch stuff), so this is pretty foreign to me.

The car has sat for a few years, but has some fresh gas. It was parked because of the problem it's exhibiting now with fresh gas. I got a new battery and the car started right up.

I didn't get a chance to drive it since it's not registered yet. But I did play with it for an hour or so. The SES light isn't illuminated fulltime. Does that mean there's no codes? I did some searching and found that on these models, you can pull the codes by shorting A-B and checking SES blink sequences. Can someone point me to a post that lists the procedure and codes?

The owner drove it around the block a few times with me sitting passenger. There's no tachometer and all the motor mounts are blown. It does feel like it's running lean sometimes. I pulled the o2 sensor (unheated) and hooked it up to my voltmeter. There's only one, right? Is this your typical narrowband 0.1v-0.9v? I was seeing 0.1v sometimes, and -0.5v at others depending on what sensors were unplugged. Spraying ether in the intake brought the reading up to around 0.4v or so. Doesn't sound like any bosch o2 sensor I've dealt with before.

But o2 sensor takes the backseat for now. I tried running with it unplugged and it still exhibited abnormal behavior, although perhaps the ECU learned based on bad lambda output?

Is there a procedure to reset the ECU? I'm going to try operating the car only in open loop until it's running right, and then reintroduce the o2 sensor and replace as necessary. The owner is on a very tight budget, so swapping parts out to experiment is out of the question. Swapping for new parts may also be out of the question, so I will likely be running to the junkyard to try different sensors out once I know they are bad.

When it does stall out, I try depressing the schrader valve at the rail, and do indeed get pressure.

How problematic is the EGR in these cars? I'm assuming that unplugging the EGR electrically will have no affect if the EGR valve is indeed stuck open, which would be causing the problem anyway?

I checked for vacuum leaks, but it looks like everything is tucked under the intake manifold and hard to get at. I will be bringing a vacuum gauge next time to check it. I found one broken vacuum hose near the back of the engine and fixed that. Afterwards, I heard no more hissing. Problem still exhibited on occasion.

I'm hoping it's either the MAP sensor or TPS. Thanks for the help! I'm trying to help a neighbor out