94 GA running rich [Archive] - GrandAmGT.com Forum


View Full Version : 94 GA running rich

09-07-2005, 01:40 PM
I'm working on a fellow co-workers Grand Am which from the back looks like it has a deisel engine in it, lol.

'94 Grand Am SE, 2.3L (VIN 3 iirc), 3-spd auto, approx 140k miles.

Anyways, check engine light almost always on, blows black smoke alot of the time, runs rough under load. I'm already thinking coolant temperature sensor but I scanned it and got codes before doing anything else. 4 codes were present - Oxygen sensor failure, Coolant sensor high, Running Rich, and something to do with AC pressure. I disregarded the last one. Looking at the scan data everything appeared to be working except the car would never go into closed loop and the gauge on the dash was about 80* different from the scan data (no biggee there, I know how accurate the gauge on the dash isn't). I had a spare CTS at home so after work she swung by and I swapped it out and cleared codes.

Couple days later she said the light still comes on but only going up hills, but all the chugging it did before went away, ok making progress. Only one code stored - O2 sensor failure again. I watched the scan data and the O2 sensor stayed right at .444V and never even budged, car never went into closed loop (obviously) so I ordered a new ACDelco O2 sensor.

Week later, replaced O2 sensor, cleared codes, and replaced one questionable vacuum line to the fuel pressure regulator. She said it runs better and the light doesn't come on as much but it still comes on every now and then and still chuggles when going up hills and/or when she's got it floored.

I haven't had a chance to pull codes again to see what it's got but I'm thinking fuel pressure regulator might be stuck shut since it only seems to be a problem under a high load situation. Only problem is there's nowhere for me to hook my gauge up to the fuel rail, unless I'm just not seeing it, any ideas? I hate replacing **** that isn't broken, especially when it's not my car and someone elses money.

09-07-2005, 02:09 PM
when you say gauge, are you talking about an oxygen sensor for fuel/air ratio?

09-07-2005, 03:25 PM
fuel pressure gauge

oh, and I forgot to mention after the O2 sensor replacement cross counts and feedback looked good and the car went into closed loop pretty quickly, which is good. Seems like alot of little problems.

09-13-2005, 12:22 PM
Ok checked the car again today, the code 13 (Oxygen Sensor Failure) came back. She says the light only comes on when the engine is under load and black smoke comes out the tailpipe. So for some reason it runs rich only under load and for some reason the ECM sees a code 13 when it does this. The O2 sensor seems to be fine (and it should since it's new), cross counts good, goes into closed loop, yata yata yata. I'm guessing that if she's hauling ass up a hill and it runs rich continuously for an extended period of time the ECM sees this as a failure? Can this hurt the new O2 sensor until I get to the root problem?

09-13-2005, 12:30 PM
Dumping alot of fuel is alot less likely to poison the O2 then say, burning coolant. On that vehicle there isn't a place to check fuel pressure at the rail that I'm aware of. An adapter might be required in place of the fuel filter.

Check the condition of the air filter and spark plugs.

09-14-2005, 12:27 PM
Ok, then I'm not insane after spending 10 minutes looking for a fuel pressure gauge port, you'd think that would be a "key" thing for troubleshooting fuel injected vehicles, I mean that's one of the basics imo, everyone wants to just plug computers in everything nowadays.

Plugs was my next thing to check but I don't have spark plug sockets at work and technically shouldn't be working on cars in the parking lot on the clock anyway. :D After I get a couple other automotive projects done here around the house I'll just get her to stop by with it.