ECU's, immobilised to be specific

[Jas11n]

Brief run down of the problem.

Traveling to VWFestival Sunday morning, fine all the way then 2 miles from the show I pulled out of a junction (not ragging it either) and at it dropped onto four cylinders. No warning, no misfire etc, just a snap drop onto four.
Both POS's are fine and were brand new in Feb, but I've bought another and it works fine, powering cylinders 1,2 and 3 ok. Switching existing POS's around makes no difference, still nothing on cylinder four.
Coilpack four was new in feb too (in fact all five replaced), but I've replaced it again and still a no show of a spark. Replaced the spark plug (which was new 2 months ago), still no spark.
Injector four is pulsing, confirmed via being able to feel the "ticking" with your hand, and also via vag-com code check and output check. Injector four now also conformed to be delivering fuel.
Wiring between coilpack and POS connector ok (to rule out a dodgy connector), wiring between POS and pin 20 of the ABY's ECU connector is ok too.

So that leaves the ECU.

I've had an offer from forum user of another immo ECU from an ABY.
Mines an immobilsed ECU too. I take it the one I'll buy will switch in and run ok?? no problems with immo's being all pedantic about it?

Thanks in advance.

Jas..

[spink]

Your more than welcome to try that ecu first Jase,shame im not going past your way again for at least a couple of weeks.

[Jas11n]

Your more than welcome to try that ecu first Jase,shame im not going past your way again for at least a couple of weeks.

Hello James,
This problem solving is moving along fast, since writing this 10 mins ago, I've organised my bro to go to the garage tonight where he'll switch his ECU into my car to 100% confirm the diagnosis of the ECU being at fault.
I'm on late shift unfortunately, so I'll not be there myself, but my bro will let me know the outcome.
I'll PM you tonight to confirm if I need the ECU for definite and to organise getting you the money/shipping etc.

Thanks for the offer, very much appreciate it mate .

Jas..

[s2avant]

If you do swap ECUs then the immo will need resetting to the replacement ECU.

You can do it in VAG-COM if you log into the Immo (group 25 IIRC). You just need to reset group 0 (again IIRC but it tells you in VAGCOM which one)

Ben

[Jas11n]

Thank you Ben, that's the info I was after

[Jas11n]

Righty oh then

It's not the ECU.

So that rules out these;

1/ Coilpack ok,
2/ POS ok,
3/ Spark plug ok,
4/ Wiring ok,
5/ ECU ok.

Still no spark from cylinder four.

If anyone can pinpoint this problem, you'll be a god.

Match? petrol anyone?

Jas

[Fat Audi 80]

Wild stab in the dark. Where does the Pos get its signal to fire from. Obviously the ECU but have you checked the cables into the POS for cylinder. Can you swap inputs to the POS's to check if this is the problem. (Obviously the firing order would be wrong when doing this but you could check for spark?)

Feel free to point out the floors in my hypothisis!

Good luck.

Cheers,

Steve.

[Jas11n]

All tried Steve I'm afraid.

I'm at a loss. With enough thought I usually come up with a hypothesis, but this has not only got me stumped, but my local specialists too who I rate very highly.

I may have to sell the car "as is" if a solution can't be found next week. A last resort, but one I'm having to consider.

Jas..

[Jas11n]

I'm going to remove pin 20 from the ECU connector and temporally route a wire to the the POS. One thing I personally have not given much thought to is the earthing of the coilpack. Local place said earth's were ok, but I'm going to try it anyway.
I'll remove the white two pin connector that carries the earth of cylinder 4 and 5's coiklpacks, indentify number 4 and hardwire it to ground.

Can't think about this anymore today, my head is going to pop

Jas..
8)

[Fat Audi 80]

Good luck Jas.

It sounds like you have thought of most things already. See if you can replicate the fault in another POS / Coilpack, that may tell you what is going on.

Don't sell. Sleep on it and you will find the answer...

Cheers,

Steve.

[Jas11n]

Cheers Steve, It's all on hold until next week now. Feskin thing.

No car means the dog might get a longer walk than usual

Jas..

[Fat Audi 80]

I thought you had 2? Audi 90?

Cheers,

Steve.

[Jas11n]

Autobox on the 90 died a week ago.

[GT500]

Aye up Jas, bit of a berger this one!

When you changed coil pack did you change plug connector?
Have you done a compression check?

[Fat Audi 80]

Autobox on the 90 died a week ago.

A R S E ! Hard luck mate.