Hi everybody!

What bothers me at my car - Audi TT 1.8, 225 HP, quattro, 2000, is:
- after 3000 rpm I have a power drop, no matter what gear I am in.
- If I take the foot off verry fast from the gas pedal I have a little rpm drop, under the idle value (under 840 rpm).
- sometimes the car doesn't start from the first time I switch the key.
- I have a very high fuel consumption al idle. If I reset the medium gas consumption counter on the bord computer and ride one mile, let's say, I have a gas consumption of 14l/100KM (I am from Europe). Then if I stop the car with the engine at idle, in a couple of minutes the gas consumption grows above 20l/100KM!
- the oxygen sensor (pre cat - the only one the car has) voltage values at idle, recorded with VAG-COM seems to be ok to me:
0.41 0.42 0.5 0.7 0.74 0.73 0.7 0.52 0.43 0.39 0.37 0.38 0.38 0.4 0.43 0.78 0.8 0.78 0.72 0.58 0.34 0.23 0.22 0.22 0.28 0.79 0.8 0.82 0.75
0.24 0.16 0.28 0.74 0.17 0.12 0.63 0.76 0.73 0.29
The graph was sinusoidal.
- I have no VAG-COM errors.
- I have checked the hoses and intercooler for leaks

I mention that I have changed the Oxygen sensor one year ago after I changed the turbocharger. The sensor was not bought from Audi though, but from Bosch, using the car chassis code.

I recently replaced the throttle body, MAF, gas filter and DV.

One year ago I have also changed the distribution, air filter and spark plugs.

So, should I change the Oxygen sensor too or should I investigate in other direction?

 

Remove the spark plugs and read them. They should be tan.
Your car doesn't have a distributor.
Also check the air filter.

 

By distribution I meant the distribution belt.
The spark plugs are ok. The air filter too.
Recently I've ran into a more serious problem. I have a loud rattling noise while accelerating. I will post it with a different topic name.

 

Change the coolant temp sensor, & it might not hurt to clean the MAF.

Lastly look for any boost leaks, & bad DV's