I have a 1995 Buick Regal, with a 3.8L engine. When I start the car sometimes it rough idles and I have to give it a lot of gas and then it runs fine. This is completely random. Sometimes it runs just a little rough, other times really rough. The rough idling when starting the car happens about 1 out of 25 times. Sometimes when this happens I get a check engine light, most of the time not. When I am driving around I also will randomly get a check engine light, but I can’t tell anything common to it. It has come on while braking, while coasting with foot off the gas and brake, normal city driving, highway driving. Also my CEL always turns off when I turn off the car and doesn’t come back when I restart the car. Always.
I haven’t been able to figure out what is wrong and since my car is transition OBD1 to OBD2 I can’t use a OBD2 code scanner (it is an OBD1 port), nor will shorting the pins in my OBD1 type port give me codes. Being this the case I took it to a local mechanic and they scanned the computer and said they got 16 error codes. They reset the codes but couldn’t get the CEL to come back on. I took it drove it for a couple of days the light came back on so I took it back to the shop and they got 18 codes out of it, but they were mostly different, with some of them giving the opposite readings of before (O2 sensor high one time, then low the next check). They said they didn’t know what was going on but wanted 3-4 hours to diagnose the PCM (Powertrain control module) and would probably replace the PCM (~500 on top of the diagnostic fee). That was a bit much for me, so I took the car back.
The things I have checked are fuel pressure (seems fine at idle and revving the car in park)
Vacuum is 19 and when I rev quick it drops to zero or so then up to 25 and slowly goes back to 19 (I think that means vacuum is ok)
I put the gage in the O2 sensor before the CAT and I didn’t read any pressure, so I think the CAT is ok.
I put on a new fuel pressure regulator, and a new fuel filter.
I got the same PCM at a Pick-n-pull place and put it is my car 3 days ago. Yesterday I got a check engine light while driving again. The mechanic will charge me to check the codes, but I think it is just doing the same thing as always.
I am sort of at a loss as what to do. I though it I was to dive around with a scanner hooked up and the light went on then I could see what the sensors were doing when all the trouble codes fire. I was looking at the Actron CP9190 for $312 on Amazon, but it doesn’t log the data stream for OBD1 cars, only for OBD2. The Snap On Ethos does, but that is like 2000 dollars (more than my car is worth). Does anyone know of some software or a non 2000 dollar scanner that would work for me, or perhaps some advice on what I should do next. Thanks a ton!