Project2point8

Okay, where to start

About 6 weeks ago my car's check engine light came on and began to get poor performance/gas mileage. It then began to stall on me. I had already made an appointment with my local mechanic, so I just grit my teeth (Not that it did it that often. Most of the time it would almost stall causing the car to jerk). The mechanic hooked up to the computer and said it was the O2 sensor going. Had him replace all 4. About a week later, it does the same thing. Take it back. He says that it has to be the ECU going out and to take it to Barrier ("Well respected Dealer in the Seattle area"). Okay, take it to Barrier. They then diagnose it, saying that they installed the mechanic installed wrong 02 sensors. Okay, so I had the mechanic put the right ones in there.

And now it is still doing the same thing.

Engine will start up. It will then proceed to idle roughly. The RPMS will level at 950, drop to almost 0, jump up to 1500, then level at 950. After doing this for a time (seems to be random, sometimes it does it in a matter of seconds, other times a matter of minutes) it will eventually stall out. It will also stall if I am driving, but because I am still moving, it essentially pops the clutch and keeps going.

I am afraid to drive my car. I have an appointment on Thursday to get it checked out be the dealer, but has anyone else had this occur? Anything I can try to narrow it down?

Thanks!

Keyless Chuck

Mileage? What kinds of preventative maint. have you done?

Carson (K03x2)

codes would help. If the CEL is on, codes are in the system. Symptoms point to the Mass Air Flow sensor being bad, but I'd get the codes read before I throw parts at it.

ianbis

if you don't have a "cel" and you have an erratic idle you need to clean your Throttle Body

por911

This gives you a good basis to work from. Check the lines for vacuum leaks. Make sure the plugs in the car are not too fouled up by now(having bad O2 sensors). Look over the usual cast of characters, air filter, fuel filter. You need to have a decent factors to work off of.
My guess is the O2 sensors were not bad(could have been though, doubt 2 sets were bad). The sensors were probably getting signals from upstream, ie MAF , coolant tempsensor(known trouble maker and has been updated numerous times), etc. You did not post the mileage of your car but if it has over 60k, you might want to think about changing out the PCV.

Project2point8

It has 90k miles on it. I had the 100,000 mile tune up done 6 months ago (Oil Change, Timing Belt, Water Pump, Plugs, Wires, Cam Seals, Fuel Filter). Other then that, just the oil and air filter change every 3k miles. When at the dealer, they updated the computer for the Cat. Recall, and double checked the swing arms (another recall).

The Check Engine light is on, however no codes have been retrieved, as my appointment (Which was on Thursday, but they were able to move it up to Monday) is not till next week. I have been greatly debating getting VAG COM, but I think this will push me over to getting it.

I will dbl check the plugs and clean out the TB. I will search on what the updating of the Coolant Sensor entails and see if I can not do that as well.

I do not have the utilities to diagnose a MAF, but hopefully the dealer can take care of that.

I really do appreciate all of your help, and the quick responses you all gave!

Project2point8

Quick Update:

Cleaned the TB and checked plugs. Plugs are fouled, but not to the point where they do not spark. However, I may have found the culprit. If it is, I think I will have to throw my towel in and just give up on the thing.

Cyl. 1 had oil all over the plug. When I checked the oil stick, it said to add. Cleaned up the plug, added oil. Let things sit fer a bit. Started her up. Let her run. After waiting for it to cool down, pulled plug again, and was again fouled with oil. This is not good. Things that come quickly to ming are either blown oil ring on the piston, or some other seal. Only piston 1 had this.

Now, I have driven cars with blown oil rings on the pistons, and they operated fine (89 Ford Ranger 2.3, darn thing will not DIE!). You ran a hotter plug and thicker oil, and that would take care of it for the most part. If the Audi is really picky, then it could cost me several hundred more to replace that ring.

I will still be taking it in Monday. Just one more thing for them to check out. When these things break, they really break...