I have a stock '99 1.8 A4 with the tiptronic in it which has recently starting driving funny. On acceleration it would jerk like a hard miss or bad fuel. So I put a boost gauge on it and its making 10psi boost at which time I get the jerk which I assume is the ECU jumping in and either pulling of spark or fuel to protect the engine. What can cause overboost on a stock car?

 

it’s not overboost, your ECU would adjust to 10psi easily… I would check coil, but first see if you have any codes…


bad maf, throttle body alignment, but definitely not overboost

 

As I understand it a stock setup is not suppose to go over 7psi - so why am I getting the extra help? I wouldn't complain except everytime I hit 10psi the car will jerk/hesitate so I'm thinking the two are related. The turbo is also louder than typical but I attributed this to the extra boost.

 

I drive the same car when I was stock I would see boost spike to 10 or 11 psi and hold 5 to 8 psi depending on RPM's. Your first step is to check for codes. If you dont have a vag com you can go to your local autoparts store and they will pull the codes for you. It sounds like you are having surging issues to me possibly a bad Diverter Valve or N75.

 

turbo should push up to 9psi, and as much as i know your ECU will except and readjust up to 16or17 psi without any mod (dv might not like that much pressure). Like I said earlier, first thing you wanna do with audis check for codes, most of the time it will point you on parts that need your attention. go to auto zone or other local auto store and check for codes, then come back here if you still have ?s.