rough cold starts

[graham_f]

not sure why, but my last thread was locked??

oh well, lets continue it here.
to recap...

the car is a 04 1.8t avant quattro with 220k. eurodyne 1+ program with the tt injectors.
I have a randomly reoccurring misfire on cylinder #2 that i cant seem to shake.

-New plugs(NKG bkr7e) and then re-gaped them...no change.
-New coilpacks, and i've moved them around... the misfire stays on cyl#2
-moved fuel injectors around...misfire stays on cyl#2
-compress test, not as good as i had hoped...but still within Bentley spec.
cyl#1 -158
cyl#2 -142
cyl#3 -140
Cyl#4 -160
straight from the Bentley Manual: New Cylinders (145-203 psi) Wear limit (102 psi) Maximum difference between cylinders 44 psi


It only happens on a cold start. The car runs like new aside from this
I have a CEL for the misfire but nothing else... vcds code 16686. I clear the code but it comes back in a day or two.
All i know is it doesn't sound happy when first fired up.

any insight for me?

[graham_f]

Re: rough cold starts

also,

today i disconnected the SAI system (pulled and plugged the combi valve vacuum hose and unplugged the SAI pump) and i'll see if it makes a difference for tomorrows start.
I know i'll have a CEL, but this should tell me if my issue is in the SAI system or not.

Tuesday's update:

-i checked vacuum tonight... no leaks there. sitting at 24.5 hg vacuum @ idle
-cleaned the throttle body and maf sensor.

i'll see if things change tomorrow morining

[PRY4SNO]

Re: rough cold starts

Weird it's only on cyl2 even after you've swapped stuff around.

Have you looked into your wiring harness? Possible it's a loose connection or frayed wire somewhere?

[graham_f]

Re: rough cold starts

ya, its weird.

there may very well be another bit of bad wiring tucked away somewhere but i cleaned up everything i saw. I peeled the harness wrap back about 16" from the injector plug and only found a little spot right by the coilpack plug.

But My thought is this... if It was just a wire issue, then why does it only happen at cold startup and only after sitting for several hours?

[onceover]

Re: rough cold starts

Try pulling the plug from cyl 2 after the car has sat for a while and see what it looks like inside.