Weird/erratic idle and part acceleration

[COBHC]

Hey guys let's see if you can help me out with this problem on my 90 TSi.

I recently checked and adjusted my ignition timing because it was firing after TDC.

The car seems to run better now, especially off boost, but there seems to be something wrong.

At idle it almost sounds like it's misfiring, causing the idle to be somewhat erratic. It also does this when cruising at low speeds (around 25mph in 3rd @ 2,500rpm) causing the car to jerk slightly.

I tried adjusting the idle speed as per the shop manual thinking it might solve the problem, but it had no effect.

I don't know if this is related but my a/f gauge reads really lean most of the time at idle.

The shop manual says to check plug gap, plug wires, compression, ignition timing,etc. The plugs and plug wires are new, I did a compression test about a year ago and it was 135, 135,130,135, obviously I just checked the ignition timing.

What could be causing this?

 

[COBHC]

Somebody? Anybody?

 

[ROOKIE1]

What else have you changed or worked on lately ? Are plugs gapped properly ? Wires in order ? Running lean , white plugs ? What type of plugs are you using (NGK) ?

 

[turbogentwo]

also check to see if you are building a lot of pressure in your upper water hose could mean you have a leaking head gasket if it's building pressure you can have a block test done on it for further info

 

[nataku80]

im having this problem too. my throttle % will cycle up and down, as viewed on my AFC. i unplug the TPS sensor and the car would run fine. when i hooked it back up it came back. like you, if im just cruising and say my throttle% is 19% it will cycle to 29% then go down to 9% and then come back to 19%. and it does this really quick. so i went to the junk yard got 9 TPS sensor and with every one it did this. so today i got a brand new one from the dealer and it still did this so im thinking, could it be my AFC???

 

[talonDSMerr]

there might be something wrong with the idle speed control or throttle body. i dont know if what you guys are experiencing is idle surge or not but heres a pretty in depth read about it and some possible sources of your problems: http://www.dsm.org/how-tos/tttt/tttt3.html

hope it helps!

 

[nataku80]

yea thanks for that page. but mine the idle is not surging just the TPS cycling. i dont know but im gonna get out there and check my wiring today to see if its all good.

 

[COBHC]

Spark plugs are NGK BPR7ES gapped @ .028, plug wires are Magnacor 8.5mm purchased just over a year ago.

I know what idle surge sounds like, it's definitely not that. It literally sounds like a misfire at idle. The weird thing is it almost seems like an electrical issue...when the cooling fan comes on the engine either cuts out for a second or boggs down bad.

Today it was smoking worse than I've ever seen it. Sometimes when I start it up it will puff a little white smoke, but today it was bad...didn't stop til I started driving it and really got it warmed up.

I need to check all that stuff like TPS, coil packs, etc. but I just havent had time.

What doesn't make sense to me is that it idled OK when the timing sucked, but now that it's where it should be the idle sucks.