Bad idling

[ur-s4315]

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. When I come to the redlights and push the clutch in it goes very nice down to idling speed.

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

- air mass meter
- new spark plugs
- all new ignition coils
- new ignition amplifiers (POS)
- 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, also tried to take one connection off at nozzle but its the same on all cylinders.
- 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 throttle it goes to -0.5 bar as it should be. Flat out 1.4 bar

MOT emission test

idling speed
CO: 1
CO2: 11.2
HC:1440
O2: 5.5
Lambda: 1.00

3000 rpm
CO: 0.99
CO2: 14.5
HC: 91
O2: 0.24
Lambda: 0.98

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

Please I need help !!!

[GT500]

Sounds rich.
I know you have tested the water temp sensor,vag com, I would have a new one on.
Is it remapped?

[kwlw]

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

Something similar occured when camshaft chain became too long for some reason. It's also was bad hot idle. He found it with some phase checking tool (they were searching for cambelt problem).

Also I would check hose between the MAF and turbo, spray MAF contacts with contact cleaner. Just in case.

Sau

[ur-s4315]

I had the hose between MAF and turbo checked and couldn't find any cracks. Have to ttake apart cylinder head cover to see if there is other camshafts than there should be. I have only owned the car for 5 weeks and I bought the car with this problem. The cylinder head was newly done with all new parts but I don't know if the chain was changed. The seller said that the car is original.

[ur-s4315]

I tried to disconnect the lambda wire but nothing happend, at idling. i also measured the TPS according to s2-central page and everything was ok.

When I give a little throttle just so that the rpm goes up to 1000 or little less then the rpm starts to to go up and down 500-1100. What can couse this? I have tried another ISV.

[UrS4boy]

When I give a little throttle just so that the rpm goes up to 1000 or little less then the rpm starts to to go up and down 500-1100. What can couse this? I have tried another ISV.

This may sound weird and it might not be the answer BUT...

On an AAN, the Intake Air Temp (IAT) sensor connector and the ISV connector are the same size and have the same number of pins. Since it seems like your ISV is not functioning properly even though you have tried other ones, I have to wonder whether the IAT and ISV connectors didn't get plugged into the wrong receptacles/devices. This HAS happened with the odd AAN owner who was working around the throttle body and didn't pay attention as to which connector went where and put things back in the wrong place when they were done. Then they post to a forum, saying "My car idles like c**p". This may have been done to your car by the previous owner.

If the distance between the ADU ISV and IAT make this error physically possible, I suggest that you swap connections to see if things get better. I doubt that they could get any worse.

PS: Are you really in the USA with your RS2?

Dave F.

[220bhp]

Had a very similar problem with revs jumping up and down on my s2, turned out to be a faulty tps.

[ur-s4315]

Hello again.

-Measured all connections at ECU, everything seems to be in order.
-checked that the camshafts were in the right position, they were.
-When the engine was warm and idling we unplugged the temp sensor at the back of cylinder head and simulated it so that the ECU thought that the engine was cold and it got more fuel. The engine started to run very smooth.
-Before the simulation the injection time was 3.4 ms. It should be between 1.5-3 ms. During the smooth running it was 3.8 ms. Sounds good but the emission showed CO=4%, HC 2000 ,which meens that a lot of unburned fuel goes through the engine.

-The bosch diagnostic tool also showed that the ignition timing was -10 at idle. Is this before or after TDC?
-How is this possible that you put more fuel in a already rich mixture and you get a smooth running?
(non standard camshafts maybe)

(camshaft markings: EX: Mon5...9258...95H IN: 034AM) are these standard?

Have to try to switch the connections. I'm from Finland but I was in a hurry when I made the profile so....

[breitling]

I have some of the same problems you are describing here.
Will try to change the engine temp sensor and intake air sensor .

Let me know if you get any wiser

[breitling]

Had a very similar problem with revs jumping up and down on my s2, turned out to be a faulty tps.

What is TPS??

[A80Avant]

yesterday after leaving the car at the garage from a small drive the day before,i went for another easy drive.The car did some very bad idling.The needle was jumping up and down while the ecu was trying to keep the car from stalling.I burned a whole lot of fuel smelling all over the place.

Today i did some checking.I dont know how to use VAGCOM very well,but from there i got no fault codes at all!Not even when the car was behaving in this erratic way!!.

SO i changed the MAF!!! why?it was the only thing that i had recently changed along with the WGFV.The WGFV has nothing to do with idle,so it seemed logical that it should be the answer,although it was a new unit bought from vagparts a month ago,but only been used for a week since i was away for the summer.

the car now behaves perfectly and everything is back to normal.I took the time to clean the ISV as well,although it was perfectly clean already when i got it out,so no problem there.

I do believe that sometimes the temp sensors could produce false readings that mess up the idle,but in tuned cars my mechanic thinks that this MAF is one of the first things to go!

so give a check on the maf once again..it may cure things...

[220bhp]

Throttle position sensor. the little black box on the back of the throttle body

[breitling]

Any updates??

[A80Avant]

Breitling,it seems that my MAF although indeed has a problem,the problem in my car was the 2 bolts on the inlet manifold where all the earth cables connect from the ECU.Since i tightened them the idle went back to normal,i have very good fuel consumption again,no black smoke.and only a 561 fault code which i suspect is from my fuel filter cause my fuel pump is also a bit louder than it should be.Check if the bolts are loose and also check the MAF again.

[ur-s4315]

I have tried another MAF from a rs2 which has no problems. I have also checked the earth connections. Tomorrow I will measure the camshafts.