bluevr6

For the first time yesterday, my S4 exibited some strange behavior.

Accelerating above 3500 rpms was rough, like a cylinder missing.

Was "soft" missing feeling, not the hard cutoff that a bad coil pack gives.
No other drivability issues.

In last 5000 miles, #5 coil pack has been replaced.

Timing belt service planned for next weekend.

Raining and cold, so I have not been under car to check hose connections (running Hoppen upgraded hoses).

Any thoughts?

Thanks,
Kevin

Sloooo4esT

sounds like possible POS, but should'nt be so soft feeling

kchin

how are the spark plugs?

bluevr6

This was kinda sudden.....

Would plugs exibit a gradual degredation of show faults out of the blue?

Thanks,
Kevin

bluevr6

I do not think its the PSO because it doesn't have the sharp and forceful cut-out associated with the PSO and the coilpacks.

Let me know if you think different.

--k

UrS4boy

First of all PSO/POSs tend to miss at all RPMs not just under boost. Therefore, it more likely an intermittent spark intensity problem. This is what I would do:

1. Take of the coil pack (the 20v turbo cover) and lay it on the intake manifold.
2. Check the torque on the spark plugs. If they only have 20K mi on them, they are probably fine. However, one of more may have backed out. Tighten only, do not back off and retighten. 22 lb ft torque.
3. If the plugs are fine and tight, then I would suspect the coil to plug boots. Examine for breaks in the rubber, etc. If you haven't replaced them within recent memory, then you might want to replace them as a precautionary measure. They are available from several people including S-cars.org, SJM Autotecknik, Arizonautohaus, BimmerParts, Parts Connection, etc. I paid $5 each for Beru (OEM) from the Parts Connection.
4. While you are there inspect the wires going to the coil. They may have cracks in the insulation, allowing leakage of current. This can also cause a short that will blow the ECU fuse (in the passenger side footwell).
5. At this point, you might want to button it all up and go for a test drive. If you still have a problem, you are going to need to check all the coils for spark intensity.
6. Disconnect all the injectors and remove the coil pack as before. WIth a coil tester from FLAPS, Pep Boys, etc. stuck in one coil at a time, have a friend crank the ignition key while you test each coil. Look for one that is weaker than the other (i.e. it will only jump the smallest gap).
7. If you have coil problem, you might want to connect Alex at Europrice and buy his new plug and play 1.8t coil pack conversion (Oops, sorry, that is STILL NOT ready for the market). I understand the price will be about $200.
8. Otherwise, try the URL. Its got a lot of hints including a bit about how POSs function.

Dave F<ul><li><a href="https://forums.audiworld.com/s4s6/msgs/85357.phtml">https://forums.audiworld.com/s4s6/msgs/85357.phtml</a</li></ul>

parkpy

I didn't exerience "sharp cutout".

I had inconsistent boost. I swapped POS, and then got my boost back.

bluevr6

Thanks for the tips Dave:

I did the pluge first thing. - all tight.
Coil boots in good shape - no cracking, no hardness.
Wires are in good shape.

Will drive tomorrow.
If still occuring, then I will check spark strength.

Peace,
Kevin

bluevr6

Ok, got in the S4 to go to work.

Cool (40 degrees F), raining.
Car drove fine up to 2500 rpm.

Once engine and oil warm, started pushing a little harder.....

3/4 throttle, accelerates smoothly to red-line
WOT, rough acceleration and a little vibration.

No Check Engine Light.

No access to Vag-Com

As an attempt at diagnosis, does anyone who has done the 1.8t coil pack swap have a known good PSO / POS they could loan me (or sell me reasonably) to do some testing?

Best regards,
Kevin

TabulaRasa

I don't know if it was bad grounds or the plugs, but my ground at the back of the valve cover had a film of oil on it.