1998 A4 1.8TQM

Ok, so I've got my car in at a local shop that deals mostly with Dubs and Audi's. I had some bad valvetrain noise and my boost was maxing out at about 5psi. They checked for boost leack - none found. "Apparently" whatever the hell that controls my wastegate is causing it to open/close(whichever makes more sense in this situation)too soon, cutting my psi of way early. He said they hooked up a boost controller and it boosted fine after that. Any idea what would cause my wastegate to have a brainfart? My first guess would be my n75. But I'm not sure. Need some opinions before I go out and spend some dough on a MBC. Thanks for your help in advance!

Josh

 

5-7 pounds of boost is normal on a stock tune. The noise woundn't have anything to do with boost anyway.

 

lol no I know the noise has nothing to do with boost. Its lifters or valves or something. And I'm peaking at 5 psi...that like uphill in 3rd at WOT. Normally at 3-4psi. The shop "said" it was running great at 10psi...but then again...I'm pretty sure they just wanted me to buy a MBC. It definitely isn't running at full hp by any means...I've got like zero bottom end and zero passing power. I thought stock boost was about 9psi...must be mistaken though. Just wanted some opinions...keep'm comin! Thanks for the response

Josh

 

The n75 is the waste gate control solenoid, but its controlled by the ecm. Maybe its sticking, youd have to get a scantool and find the pulse rate of the solenoid to see if the solenoid or ecm is casuing the low boost.

 

Have you hooked it up to a VAG Com?
THe only way to really see what's going on is to due some boost logs on block 115.
Then also do the N75 duty cycle.

Have you checked the N249, and DV's?

What oil are your using? Usually valve noises are the lifters not getting to the proper height.
That is usually a oil viscosity thing, related to heat, bad oil choice, & water/fuel in the oil.
Change it with a slightly higher weight & see if the noise goes away.

 

Unfortunately I don't have access to a Vag atm...might just break down and buy one. Car has a brand new forge 007 in it so i doubt its that. As for oil...I'm using Mobil 1 5W-30, I might bump it up a bit and see if that helps. I can live with the "low" boost, but its the valve/lifter noise thats driving me crazy. Had a compression test done and I was 155 across the board. Sounds like its coming from the top/back of the engine. Thanks for all the replies. I'll see if I can find someone in town who will scan for codes and whatnot for me today.

 

Audi recommends 5w 40 or 0w 40 depending on climate conditions.

 

Here is a simple suggestion...are you sure your boost guage is accurate?

 

Its about .5psi low. I am more concerned with the engine noise than the boost issue. pc-16 in the near future so I will find out then if I am actually running low.