Bad idling

[ur-s4]

Hello

I have a serious problem with my rs2 -94. At idling and low rpm the car goes and sounds like a V8. It is confirmed that a lot of unburned fuel goes trouhg the engine at idle and low rpm but when the boost comes up it runs as it should and max boost is 1.4 bar. In the morning the car runs very nice the first 1.5 minutes and then it starts vrom vrom vrom idling speed 750 ->850 up and down.

Following things has been tested or tried from a another rs2:

- air mass meter
- new spark plugs
- all new ignition coils
- new ignition amplifiers
- pressurized the intake system, could not hear any leakages
- changed all small vacum hoses
- cambelt is right
- another ISV
- no fault codes
- engine doesn't use any oil
- no black or white smoke
- fuel pressure is ok
- injection nozzles pressurized and tested
- magnetic (n75) valve tested
- compression ratio is ok
- cylinder head is leaktested and ok
- air temp engine inlet ok according to vag-com
- engine temp ok acc. to vag-com
- new lambda
- no leakage in crankcase breathing hoses
-
- at idle there is only -0.2 bar vacum in the intake manifold and when I blip the thrittle it goes to -0.5 bar as it should be. Flat out 1.4 bar

Is it possible that the inlet camshaft could be 1 teeth wrong?

Please I need help !!!

[tom1]

I have to say i havent got a glue:( but post this onto the www.s2forum.com aswell and good luck:)

[AAH!]

Is it possible that the inlet camshaft could be 1 teeth wrong?

Unlikely at that would put you into limp home mode i.e max 0.5 bar pressure.

When my car intermittently and erratically sounded like a V8 it turned out to be a failing POS (Ignition Coil Power Output Stages) which made the car fire on only four cylinders.

I'm not sure if what you have called "ignition amplifiers'", which I see you have changed are the same things, but I guess they might be.

Do you know if all cylinders are firing? Once your car is running badly try unplugging and replugging the injectors one by one and see if it makes a difference - it should on all but one cylinder.

Maybe there is a bad connection or wiring issue, but it could be worth reinvestigating that area.

Have a look at this post on the S2Forum from when I had the problem:
http://www.s2forum.com/forum/showthread.php?t=11198

Also look here for some more and very useful troubleshooting ideas:
http://www.sjmautotechnik.com/trouble_s ... nition.htm

HTH

Angus

[AAH!]

Is it possible that the inlet camshaft could be 1 teeth wrong?

Unlikely at that would put you into limp home mode i.e max 0.5 bar pressure.

When my car intermittently and erratically sounded like a V8 it turned out to be a failing POS (Ignition Coil Power Output Stages) which made the car fire on only four cylinders.

I'm not sure if what you have called "ignition amplifiers'", which I see you have changed are the same things, but I guess they might be.

Do you know if all cylinders are firing? Once your car is running roughly try unplugging and replugging the injectors one by one and see if it makes a difference - it should run really roughly every time you disconnect a injector on all but one cylinder, once you have established which cylinder is not firing you can focus your attention on the associated wiring and see if there is a bad connector or damaged wiring issue or even a faulty POS.

Have a look at this post on the S2Forum from when I had the problem:
http://www.s2forum.com/forum/showthread.php?t=11198

also do a search on the S2Forum using POS

Also look here for some more and very useful troubleshooting ideas:
http://www.sjmautotechnik.com/trouble_s ... nition.htm

HTH

Angus

[AAH!]

Is it possible that the inlet camshaft could be 1 teeth wrong?

Unlikely at that would put you into limp home mode i.e max 0.5 bar pressure.

When my car intermittently and erratically sounded like a V8 it turned out to be a failing POS (Ignition Coil Power Output Stages) which made the car fire on only four cylinders.

I'm not sure if what you have called "ignition amplifiers'", which I see you have changed are the same things, but I guess they might be.

Do you know if all cylinders are firing? Once your car is running roughly try unplugging and replugging the injectors one by one and see if it makes a difference - it should run really roughly every time you disconnect a injector on all but one cylinder, once you have established which cylinder is not firing you can focus your attention on the associated wiring and see if there is a bad connector or damaged wiring issue or even a faulty POS.

Have a look at this post on the S2Forum from when I had the problem:
http://www.s2forum.com/forum/showthread.php?t=11198

also do a search on the S2Forum using POS

Also look here for some more and very useful troubleshooting ideas:
http://www.sjmautotechnik.com/trouble_s ... nition.htm

HTH

Angus

[ur-s4]

Yes I mean the POS. All cylinder are firing, I tried to unplug one at a time but no difference between the cylinders.

[alastairg]

Multi-Function Temp. Sensor-Defective?

One additional sensor to check when having low boost problems (1991 200Tq 20V Only) , is the Multi-function Temperature sensor.

This sensor is mounted underneath the intake manifold, on the coolant pipe on the 20V Turbo Engine.

This Multi-function temp sensor uses a 4 terminal connector which is normally is covered with a protective rubber boot. The newer style replacement Sensors will have only 3 terminals as they simplified the internal design of this sensor and eliminated the +12V supply to this sensor.

Go to 20V Engine Multifunction Sensor section for more details on this sensor.


From the sjm site Angus put up as a link also more here http://members.aol.com/c1j1miller/index.html Its an easy test just disconnect plug (you will lose coolant temp display)from sensor

[ur-s4]

ABY, AAN, ADU engines ECU doesn't use the multi function temp sensor.

[alastairg]

AFAIK it does. See these http://www.s2forum.com/forum/search.php?searchid=411156

[alastairg]

I note this on the sjm site Note: The 1992-95 Audi S4/S6 Engine Control Unit (ECU) does not use this over temp signal from the Multi-Function Temperature Sensor to lower boost when the engine overheats, it uses the signal from the ECU coolant temperature sensor mounted at the back of the cylinder head. But I thought ABY/ADU did use it. You may be right I shall do some more digging

[alastairg]

Ok then why not look at the coolant sensor G62 at the rear of the block which does talk to the ECU. Again from experience have you checked the WGFV connections. I got intermittent mechanical boost only with a loose wire that gave no codes and failed the VAG COM test after initially passing it (thanks to Mihnea at MRC).

[alastairg]

ANN No
ABY/ADU yes see link http://s2central.net/motronic_pinout_ABY.html

[stevechiu]

any result concerning bad idling from Neutral.I think I have similar situation

[alastairg]

Double checked with Paul Nugent 'Mr S2 central' and I quote 'The ABY Motronic manual dated 09.92 however clearly states (Page 24-79) that MFTS is used by the ECU at pin 46. If the voltage on the R pin is greater than 2V then everything is normal. If R pin voltage is below 2V then boost pressure is reduced. My ABY schematics agree with this, showing a blue/white wire from MFTS pin-R that connects to the ECU on #46 via one of the cylindrical connectors on the wiring loom in the engine bay - T8f pin #5.

I expect the RS2 will follow ABY logic.

[ur-s4]

No results yet. Have to check that the inlet camshaft marks are towards the exhaust. I also measured the TPS according to s2-central manual and it was ok. I don't think it's the MFTS because otherwise it wouldn't get full boost 1.4 bar (If R pin voltage is below 2V then boost pressure is reduced). Does the WGFV have anything to do with the idle?