Hi guys,

This is my second Audi, I still have a 2001 S4, but found this little A4 1.8T cheap and thought why not. Had it one day and I have discovered that there is either no turbo boost happening, or this is really gutless.

I have researched for a day now looking for solutions and have found lot's of suggestions some of which I have tried. I have VAG and found 4 codes in the engine, the one most likely relating to my problem is 17965/P1557 - Charge Pressure Control: Positive Deviation. The others were 17972 - Throttle Actuator (J338): Under-Voltage during Basic Setting, Intermittent17967 - Throttle Valve Control part (J338): Fault in basic settings, Intermittent16688 - Cylinder 4 Misfire Detected.

I am not sure if you should be able to hear the turbo, but I sure can't, and by driving it there is no boost. I have checked the vacuum lines and rubber boots, hoses etc, I don't hear any wooshing or weezing like there is a leak, but I am about to go out and do the tennis ball test. I cleared the codes and drove up and down the street and nothing has come back.

I found a document on what blocks to record in VAG but my computer doesn't have a lot of them, like 115 boost specified and boost actual, mine says NA. 032 should be fuel trims, mine I think shows lambda (which I think is O2 sensor related??) MAF on block 002 seems normal. So do these older cars not have blocks I have mentioned?

I'm heading back out to pull off the air filter housing and get access to the turbo and N75 valve, do the tennis ball thing and report back.

Looking forward to any ideas you have.

Oh it's a 5 spd car with 200K miles on it, timing belt just done this summer, oil and air filters changed, new O2 sensor at the CAT.

Cheers

 

Well tennis ball test revealed no leaks that I could hear. I just did some more reading and found a somewhat common problem on these turbos, loose or fallen off wastegate flappers. I can move the actuator rod with a long screwdriver, but the rod doesn't move at all by itself when revving the engine, which I think it should if everything is working correctly. So what moves the rod, pressure inside the turbine or the vacuum actuator via N75? or a combo of both?

Think I'll pull the cat back away from the turbo tomorrow and see if the flapper is missing or jammed open somehow.

Cheers

 

So for those of you who come across this thread and have a similar issue, I found the problem, as I thought, the waste gate flapper is GONE, down the exhaust pipe somewhere. I found a turbo from a jetta, which is a different mount but looks to be the same size flapper, I'll cut it off and weld it on mine and should be good to go.

Cheers