Overboost doesn't necessarily put any lights up on the dash.
Overboost typically has the following symptoms:
- Worse when hot, seldom initially from cold but getting worse over time (if turbo related rather than being N75 valve)
- When it happens, stopping, turning off the ignition and re-starting will put things back to normal for a while. The OP should try this.
- Sometimes, when climbing a long hill in high gear, the problem will kick in and power will seem to fade away. The harder you press the pedal, the more power fades. The trick is to accept what you have, feather the throttle as much as possible and hope that the bus you just overtook doesn't get too unhappy when you are slowing him down. Dropping to a lower gear doesn't help much.
- Completely intermilltent - can happen five times in a day then the car car drive fine for a week. This rules out several causes, including leaky vacuum pipes.
The OP doesn't say whether the car is manual or auto, but the symptoms can be even more frustrating on an auto because the engine ECU/gearbox mechatronic combination conspire together to try and achieve what the driver is requesting with his right foot, but at the same time keep the car in limp mode to avoid blowing the engine up. What you expereince can then be very misleading. Been there, done that!
But as you quite rightly say, a code scan is the first start.
I can't see it being the carpet, because the Passat has an organ pedal throttle that is more difficult to wedge the carpet under and in any case, the symptoms would be ameliorated by changing to a lower gear.
MAF often doesn't put lights up on the dash either and also sometimes doesn't throw up any codes. It is frequently suggested as the first choice for this sort of thing and is easy to check and eliminate just by disconnecting it for a while, but sadly it's usually not the cause.
One other cause that a code scan may point to is a failed MAP sensor. It is cheap to swap for about £80, and easy to do providing its location is accessible. Sometimes, the front bumper has to come off to get to it. I've no idea where it is on the OP's car.
But code scan first.
p.s. My first visit to the forum, 6 years ago was with the very same symptoms and after 3 months of various garage attempts to fix it. I feel your pain.
