Hey Scotty,
Bought a 1994 MGM with about 100K on it. Had a major vacuum leak when I bought it and was running rough while under load and had a rough idle/stalling issue until warmed up.
Found and fixed a major vacuum leak. Idles much better now. However is still stumbles really bad (maybe misfire) while accelerating and has little power. No CEL on. No smoke out of the exhaust.
It does have a noticeable exhaust leak on the passenger side. Have not determined exactly where yet but it appears to be before the cat. I checked plug gap, wires, ohmed out coil packs (same readings on both packs). I changed the fuel regulator because I happened to have one in the garage. Fuel pressure appears to be good. I unplugged MAF and TPS which seemed to have no effect. I also ohmed out the injectors to which they all check out good. I also checked temp pre and post cat on each bank. Drivers side is 550 before cat 450 after, passenger side is about 400 before cat and about 380 after. However passenger side has the exhaust leak so I'm guessing that is the reason for lower temp on passenger side. Not sure if the drivers side cat is plugged or if I'm just chasing my tail.
I don't hear any chain slap or noise coming from the timing chain so I don't believe it's that. I also sprayed around with some Brake cleaner and couldn't find any other vacuum leaks.
It's a beater so I don't want to just throw money and parts at it but it's been a while since I've wrenched on any OBD1 vehicles.
I'm thinking plugged cat on drivers side or maybe the exhaust leak is bad enough on the passenger side that it's causing a major misfire/losses of power?
Big fan of your channel and I look forward to hearing from you!
Not sure if the drivers side cat is plugged
based on the temps you measure, it does sound like it.
https://www.autozone.com/diy/catalytic-converter/symptoms-of-a-clogged-catalytic-converter
https://www.youtube.com/watch?v=tLos00sPhr0
you could also try measuring backpressure
@imperator Can't measure back pressure with the exhaust leak unfortunately. I just cut the cat out for the hell of it. Was definitely plugged up. Car seems like its breathing better but is still misfiring/running really rough on acceleration. Finally triggered a CEL. Have to figure out where the EEC plug is and how to jump it to retrieve the codes. It's been many years since I've had to do that.
Also put a new fuel filter in because why not. Made no difference.
there's a few tips in our FAQ you can try
@imperator Codes came back (332) EGR Valve not opening. (172) Lambda sensor (right) too lean. (176) Lambda sensor (left) too lean. EGR valve working properly. Solenoid was bad and was replaced. Codes are gone now and no CEL. Still has bad tip in. Going to change the MAF sensor tomorrow. If that doesn't do it then I'll do a compression test. If that checks out I'm not sure where to look at next. Maybe replace the coils just for the hell of it.
It's getting to the point where it's not even about the car anymore, I just want to win.
nice work. Thanks for posting your solutions.
@imperator Just a follow up incase anyone is following or in a similar situation. Slept on it last night and decided to just spend the 80 bucks on a new MAF. I unplugged the old one a few days ago to see what happens and it made it idle/accelerate even worse so I had assumed it was working. Even though all the symptoms to me felt like a bad MAF. So said screw it and threw the new one in. We're running like a top now. Wish I would have just done that to start with but I'm pretty adamant about not just throwing parts and money at something hoping it works.
I think between the vacuum leak, bad EGR solenoid and the plugged cat it was enough to throw me off the trail of the real culprit.
Anyways. All is well and thank you for the input!