eharder

I just bought back an '01 TT that I'd sold to a friend of mine a few years ago. The car recently began running badly, he wanted a new car and made me an offer I couldn't refuse, so back it came.

The issue began as an intermittent one. The car would run a little rough and then run fine. Sometimes the CEL would come on, other times not. The problem is now constant, regardless of time running, etc.

The engine is running very rich, and poorly at any speed or RPM. Plugs were all heavily sooted. New plugs did not improve the issue. Inductive pickup test tool shows all coils are firing (although of course not how well). Swapping coils around had no impact on codes thrown.

Feedback from mechanic is misfire codes on all cylinders, which I'd expect. The bizarre part is readings of 975 bars pressure and high coolant temp with the key on, and then 1000 bars at idle.

I'm hoping between these symptoms and readings that there's a common issue/failure to start looking for.

I'd appreciate any input on where to begin sorting things out.

Kind thanks.

Mister Bally

Throttle Position Sensor needs to be cleaned or replaced. I've discussed this on the D3 A8 thread.

eharder

Never would have thought to go there.

Thank you for that!

Mister Bally

You're welcome.

eharder

No improvement after disassembling and thoroughly cleaning the TPS.

Plugs have been replaced
Disconnecting MAP and MAF made no changes in engine running or engine readings
Engine load reads 100% and shows sensors show pressure between 1015 and 1020mb

Current codes thrown:

18010 & P1602
16684
16687

Beginning to wonder if the ECU has issues.

Mister Bally

Check timing belt for correct installation. Camshaft marks vs Crank pulley marks.

eharder

I appreciate the input, again.

The engine was rebuilt including a new head and timing belt after it failed about 10k miles ago. The problem was intermittent at first (perhaps once a week at the onset), and ran fine the remainder of the time until it stayed running as it is now.

Given this, would you still consider a cam timing error?

Mister Bally

Definitely verify camshaft timing. One tooth off on the crank is huge. one off on the cam istill bad, two off is worse and three off equated to crushing valves. The stored diagnostic codes from the Check Engine Light should provide a clue. You need to use the Ross-Tech software & cable or the genuine VW shop tool. Don't waste your time with a $30-$100 scan tool-they won't help.

Perhaps the cam position sensor is intermittent. Once you inspect the belt for correct positioning and verify, pull the valve cover and verify if both cams are set correctly related to each other. In case one is off one slot in the chain.

There are also crazy vacuum lines and related things that can cause this. Again, a proper diagnostic scan is part of standard troubleshooting techniques with these vehicles.

If the "new head" was a genuine VW/Audi rebuild or brand new part (big dollars for a brand new from there) then you shouldn't have to worry about the chain being off but you never know. If a shop that does not specialize in these beasts rebuilt it or if you did it yourself, double check it.Have a new Valve cover gasket on hand. WHen you pull the cover, also check the head bolts for proper tightness. Although you could just perform a compression test to verify.