Help!! Post TB change misfiring. W/ obdii codes.

[my_01_S4]

Recently I had the timing belt done on my B5 S4 ('01). This is a stock (ie non-tuned) set-up.

Prior to it, I did occasionally get the check engine light for multiple misfires (including specific OBDII cylinder misfire codes) but only on a rare occasion during HEAVY acceleration.

While leaving the shop, I immediately noticed the strange drop in power and engine stumble as if I had bad gas or one of the plugs was somehow fouled.
This happens any time I accelerate moderately, not just during heavy acceleration.

I brought it back to the shop the following morning and asked them to check the timing in case it was off. Later that afternoon, they said they checked it & it was ok. They did find 2 cylinders with really low compression (70-75psi) while another had moderately low compression (125psi) & a couple of plugs were fouled.

I'm suspicious of their analysis of what's happening because it's just too convenient that it happened right after they did the timing belt!!

The codes I'm currently getting are (obtained w/ a generic OBDII reader)...
P1140: Water in fuel!?!?
P1122: TPS circuit Intermittent Low voltage
P1138: Lack Of HO2S12 Switch - Sensor Indicates Rich
P1136: Fan Control Circuit Malfunction
P0300: Random/Multiple Cylinder Misfire Detected
P0305: Cylinder 5 Misfire Detected
P0507: Idle Control System RPM higher than expected

I'm having difficulty seeing how some of these are related.

FWIW, I have cleared the codes and within a minute of driving (moderate acceleration) got them again.

Any idea's what I should be looking at? Badly done timing belt change (1 or more teeth off?). Is it likely I am just unlucky & actually got a burnt valve right after my timing belt change?

I'll be bringing it to the local high end Tuner shop (Streetwerke in Palo Alto) to have this fixed but am curious what the general consensus is here on what might be causing this?

TIA

[RolledMySTi]

If two cylinders are low compression you could have some bad rings or valves. I would suspect valves more. It's going to be really hard to say that the shop and their TB job was the cause. If you were getting misfires before maybe the new TB just brought those problems to light. Either way good luck because it sounds like and expensive fix.

[my_01_S4]

If two cylinders are low compression you could have some bad rings or valves. I would suspect valves more.

Agreed.

It's going to be really hard to say that the shop and their TB job was the cause.

True.

If you were getting misfires before maybe the new TB just brought those problems to light. Either way good luck because it sounds like and expensive fix.

Hmmm, I'm not a mechanic but I do fundamentally understand how engines operate. That said, I can't see how a new timing belt would make the problems occur more frequently since the timing wasn't off before so there was no operational or functional change by replacing the timing belt unless they miss-timed it and the timing is now off.

Can the timing belt/pulley alignment be checked w/out removing the front end to access the belts/pulleys?

[JackalS4]

A lot of stuff gets moved around/touched when doing the timing belt.

I'd say hold them responsible for now, they're going to have to check over their work - you noticed the problems right after they were finished after all...

Just out of the air it could be something like timing off a tooth, crank angle sensor, improperly re-installed coilpacks or many others...

Good luck...

[my_01_S4]

Well,

I'm gonna take it to a local 'reputable' shop who specializes in VAG vehicles. Hopefully they'll find that the other shop screwed up a bunch of stuff and fix it for alot less than an engine rebuild.

Additionally I know for sure, I'm gonna need to replace a turbo. No, not going to upgrade to a K04 cause it's my daily driver and I already have enough expensive hobbies. I just want a reliable, running, and relatively quick car right now

I can upgrade it later if I really want to.

BTW, I recall reading that it is possible to access and R&R the turbo's by supporting the engine/tranny and removing a cross member or something like that.
1) Did I recall that correctly?
2) Has anyone documented this in a post with pictures? I tried searching w/out success so a link would be greatly appreciated.

TIA.

[HighDesertAudi]

If the shop didn't use the crank lock bar, your timing could be off slightly even if they didn't skip a tooth. If it's severe enough it could cause the misfiring and bad compression.



PS don't put K03's back in if you're looking for reliability and just pull the engine it's not that much more work.

[haus4]

if your timing belt is off a tooth, you would have bigger problems. Thats why its so important to use the lock bar, or be super careful. Im guessing they shook some things up when installing the TB.

First worry about the miss fires. Then see about the fuel in gas thing. that seems kinda weird if your car was in a shop.

see wat the other shop says, bc it looks like somebody could of fooled with something. Just bc there are so many different things, especially if you didnt know of any problems before goin into the shop.