Help please !!!

[Martin62]

I took my ABY Coupe into work on Monday, 60+ mile round trip and everything was normal.

Got home, all OK. Went out to the car 10 mins later and it started on 4 cylinders only so I left it and used another car.

Went out to it last night to put it away in the garage and it started on 5 but after 30 seconds or so was back on 4 again.

Pulled the codes tonight and no issues, Changed plugs as they really needed doing but no change, still 4 cylinders.

As none of the plugs looked wet I started to suspect fuelling as the issue so with the engine running i pulled off the electrical connection to cylinder 5 injector and it made no difference. To confirm, I did the same to the connector for cylinder 4 injector and the revs dropped etc as you would expect.

This points to either a duff injector or no electrical supply to it so my questions are:

1. Does my logic seem reasonable ?
2. Does anyone know the resistance value I should see when measuring across the injector terminals?
3. With the engine running, what voltage should I see across the injector supply terminals ?

Any other advice / direction / experience as always would be greatly received.

Thanks.

Martin

[twoqu]

http://www.s2forum.com/forum/showthread.php?t=76334&highlight=injector+connector

[twoqu]

If you have VCDS you can perform the output test to check the injectors.
Resistance is 15-17 ohms according to the Factory info!

[Martin62]

Thanks for that useful info. Unfortunately I only have a basic reader so I cant perform the output test.
I will check the injector coil resistance and supply voltage and see where that takes me.

Thanks Again !!

Martin

[twoqu]

No problem.
Of course the injectors should have battery voltage at the No2 terminal with ign on. The earth return is more difficult to test as its controlled by the ecu. Depends on what you have available to measure it.
If it repeats dropping out after a while it does sort of indicate a dodgy injector rather than a wiring issue. A short would throw a code.

[Martin62]

Well the plot thickens, I have just checked the coil resistance and it's 19 to 20 ohms which is the same on all 5.
With ignition on but engine not running, the supply voltage measured across the 2 terminals is 11.6v which is the same for all injectors.
I started the engine briefly and held a screwdriver to my ear with the other end on the injector body and I could hear it clicking away and there was also a smell of fuel so I now suspect it's an ignition fault not fuelling despite not seeing a wet plug when I swapped them....my mistake.........so now I need to check the ignition system.....any suggestions where to start ????

[twoqu]

Ah! If you go back to that link I gave earlier and scroll to the bottom there is a link to swopping the POS pins. Of course it could be a coil but you have to start somewhere I guess.

[Martin62]

Thanks for your help, I will have a look at it tomorrow evening.

Martin

[twoqu]

http://forums.quattroworld.com/s4s6/msgs/153152.phtml

[mike74]

Sounds exactly like when i had a coil playing up a couple of years ago. It would run faultlessly then drop a cylinder for no reason.

[Martin62]

I will follow the diagnostic approach tomorrow as suggested and see what happens, I just hope it's something simple but whatever it is I'm sure it won't be cheap, unless it's a POS channel swap of course !

Cheers,

Martin

[piotr]

It might be one of ignition amplifiers
IMG_4806.jpg

[Martin62]

Finally got around to fixing the fault this week. It turned out to be a duff channel on the POS N127. Swapped pins to use the vacant channel as described in UrS4boy's excellent post and all is well. Colour codes are slightly different on the ABY which I picked up from S2central but that was the only complication.

Thanks to all for your responses, never fails to amaze me how much knowledge forum members have !!!

Cheers,

Martin

[macspring]

Thanks for updating / 'closing out' the thread.

Few of us would be able to do as well as we do running these S cars without this forum.

[newsh]

Excellent!