1998 A4 1.8t that intermittently will loose power while driving and also have no power gain above 4k rpm. Any ideas???
Thanks

 

Is this a new car or something you noticed over time? The turbo craps out a little above 4k rpm's, and they are slow to begin with in stock form. You can get your ecu scanned for fault codes that don't trigger the CEL and post them if there are any.

 

Have had ecu scanned and the only faults are for parts that have been replaced. Turbo has even been replaced and this still happens.

 

Boost leak, or your DV is getting stuck open (depending on what DV you have). I have a early 99 1.8tq. Before I bought it someone bought a POS vacuum line for the run from the intake manifold to the DV. It would randomly pop off of the DV and would create the problems that you speak of. A little bit of boost, but no real umppff...... ECU never detected a positive deviation??? Other times my aftermarket DV would get stuck open and would randomly close, causing weird boost. Just start checking your vacuum and boost lines to make sure you don't have a boost leak.

 

JR,

Thanks, I will check to see if the DV is sticking open or something. We have checked all hoses many times over for vacum leaks but have found nothing. Hopefully you are onto something here.
Cheers

 

Pull out the n75 and test ground on the harness then test for duty cycle

 

install a boost gauge and see where your boost is.

 

qft..

 

whats "qft"?

 

'quoted for truth'- or 'quite f*ckin true' depending on who you ask.

installing a boost gauge is a very good idea, theres really no easy way of troubleshooting your turbocharged car without one. its a cheap and simple install everyone with a turbo or supercharger should do.