02 grand prix isn't happy

[Eric Wettschreck]

2002 Grand Prix, 3800 engine, 135K miles.

I've had this car for aboot a year and a half with no real serious problems.

I drove it home from work last Friday, put it in the garage, and walked away. Spent the weekend living in the fish house. I started it up this morning, backed it out of the garage and walked back into the house to let it warm up. When I jumped in it everything was good. I put it in gear and it died. Ok, it's -18, nothings happy when things are this cold. Re-started, put in gear and it died. No check engine light. Re-started, idled fine, put in gear, and backed out of the driveway. When I got onto the road I hit the foot feed and it died, check engine light came on. Re-started, had to feather the foot feed to keep it running, pulled back into the driveway and it died. Re-started, feathering foot feed, pulled into garage. Started truck, went into house for a few minutes, and went to work.

Got home from work, started the car, drove it aboot 5 miles down the road and back, and it ran fine. Put the code reader on it and got the following.

1. P0420- Catylist system efficiency below threshold Bank 1.

2. Pending code- P0101 Mass or volume air flow circut range/performance problem.

Cleared the codes, took it down the road aboot 5 miles, came back............everything ran fine, no codes.

I'm thinking, "This is kooky." so I messed around in the garage a bit with the car running at idle. Drank a 6-er. Fixed my auger. Still no codes. Neighbor came by and I had him take it down the road.................no problems, no codes.

I fix machinery for a living and I know things don't fix themselves so I have a few questions.

1. What the heck????

2. Where do I start?

3. I don't know what bank 1 is. I'm guessing (emphasis on guess) it's the 02 sensor on the exhaust right behind the manifold, and not the one one the output side of the cat converter...am I on crack?

I know this has been discussed in the past but I can't find it using the search feature. I have a 30 mile commute at 3:30 am on a county road that has zero traffic so I can't be broke down. I sure could use some advise on what to start looking at/parts to be replaced.

Thanks fellas.

[Macgyver55]

Bank 1 is always where the #1 cylinder is. If I'm not mistaken it is the front bank on that car.

Aside from that MAF sensors are a common issue on that vintage car as are the connector that goes to it.

If it acts up again try unplugging the sensor and it should run enough to drive it so you won't be stranded.

[Dozer]

The P0420, is comparing the upstream and downstream (before and after the converter) o2 sensors. Its saying your converter isnt working. I dont think this has anything to do with the car dieing but if you want to fix it without replacing the converter Google "sparkplug nonfouler o2 sensor fix"

[Jeremy airjer W]

Or with the engine running and the trans in park wiggle the connector for the MAF sensor. If you hear an rpm change, or the engine stalls replace the MAF and the pigtail and you should be good to go.

The 420 code is telling you the cat is no longer doing what it is supposed to do. There is only one cat and it is after the rear manifold. If you decide to replace it go with a quality unit rather than a cheap unit.

[Macgyver55]

I've run into p0420 codes because of bad MAF sensors though, so before doing anything with the cat I would make sure that the stalling problem is fixed first. If there is a MAF sensor problem and you repair it, there is a chance the p0420 code may not return.

[Eric Wettschreck]

Thanks guys. So far I haven't done anything.

I drove it to work this morning with no problems and no codes popped up.

Weird.

[Scott K]

Bang on the MAF with your fist, does it miss? Or cut out? If it does, replace it.

[Eric Wettschreck]

Bang on the MAF with your fist, does it miss? Or cut out? If it does, replace it.

Wiggled the wires, got nothing. Gave it a smack and it started cutting in and out. (I'd be PO-ed if you gave me a smack, too)

Time to replace a MAF.

[Jeremy airjer W]

The reman units are awful tempting as they are less expensive but they are also less reliable. We Do not install remans at the shop anymore. To many time the reman MAF sensors would make the car run worse if it would even run at all. New a/c delco is the way to way to go. The NAPA unit is a relabeled a/c delco. At one time you could peel back the Napa sticker to reveal the o.e. Sticker.

[Eric Wettschreck]

Good to know. Thanks Jer.

Car has been sitting in the garage for a while cuz I"ve been out fishing. Have not replaced the MAF yet.