Running on 4 cylinders only?

[tscheel]

Suddenly one cylinder down.

History - bought the car in May - 1994 ABY - 235000km, samco hoses, RS2 exh. manifold, 3" downpipe and exhaust, metalcat, Ultimot chip. Coils and injectors original I believe. 265hp in june.

VAG COM 409.something gives some 561 fuel adaptation (both too low and too high) (from memory) - definately no errors on coils or injectors. Output test - no sounds from any of the injectors. Other outputs OK.

Please kick me in the right direction - How do I test individial coils? The injectors - do I just disconnect and measure the plugs one by one with the engine running?

Thanks in advance

EDIT : one POS channel (#2) was down on the one driving 2 coils - switched the green wire from terminal #3 to #1 in the input plug, and the corresponding black wire from #2 to #3 in the output plug.

The best rides are the test rides when a repair is finished

Thank you very much Merlin, prj and also UrS4Boy and Mr. Nugent for the detailed info provided. Beers all around

:mischeif:

[merlin's S4]

You can work out which cylinder is down by disconnecting the injector plugs one by one whilst the engine is idling. When you pull each one it will either make the engine run worse or make no difference. The injector that makes no difference to the running of the engine points you to the cylinder which is down.

I would suspect either a coilpack or POS problem. You can check the POSs by swapping them and seeing if the non firing cylinder moves to a different cylinder.

[prj]

Also don't run the car like this for extended periods of time.
If it is one of the coils that has went, then make sure you find and unplug the cylinder, otherwise you will foul the spark plug and wash lots of fuel down the bore...

[tscheel]

You can work out which cylinder is down by disconnecting the injector plugs one by one whilst the engine is idling. When you pull each one it will either make the engine run worse or make no difference. The injector that makes no difference to the running of the engine points you to the cylinder which is down.

I would suspect either a coilpack or POS problem. You can check the POSs by swapping them and seeing if the non firing cylinder moves to a different cylinder.

Off to the garage then

Forgive My ignorance - the 5 coilpacks are on the cam cover and the 2(?) POSs are on the bulkhead, right?

I won't be driving the car until this is fixed.

I'm looking into the RS6 coilpack upgrade - I have a spare 7A camcover, so if it's a coil or pos problem, I won't be hesitating.

[tscheel]

Work and learn - cylinder #5 was he culprit - until I switched the POS plugs - then it was cyl #2. Perfect error detection - thanks!

Now - off to the search engine for a description of switching coil #5 to the unused POS output.