Idle problem...

[Enne&Effe]

Hi all
I have another problem with my B5 RS4 (remapped ASJ engine): sometimes at idle the revs are not constant and "dance" from 500 to 1000 rpm. In the meantime I see some black smoke coming out from the exhaust and smell fuel odour.

If I start driving, the ECU is in limp mode (no turbos.....); I have to turn off and on again the engine to get full boost.

During this problem at idle, I tried to unplug the MAF and immediately everything went ok (just replaced all lambdas but the issue remained the same).

Does anyone experienced this problem?
Should the MAF be replaced or simply cleaned?

Thanks in advance for your support.

Enne & Effe from Italy

[mattykerby01]

I would in the first instance get the car plugged into VAGCOM and find out what faults codes have been logged on the ECU, then you should know what your dealing with.

[Enne&Effe]

Sorry I forgot to tell you the VAG COM output, that's why I'm asking here....

Rough idle: no problems.....
Limp Mode: Charge pressure maximum limit exceeded (tested both with remapped ECU and stock ECU: no differences)

[Harper--D]

Sounds like it could be an injecter o'ring has nakered. Take the y pipe off and see if you can see any fuel around any of the injectors. If not start the engine and see if there is a hissing sound coming from any of the injectors!! That could be why you can smell the petrol and the car being in limp mode!
Dave.

[s4woody]

you wont see any fuel leaking from an injector but if you worried that your injector seal mite be faulty then with it running spray some WD40 at the base of the injector and see if the revs rise at all..
check all the vacuum pipes on the engine including the 1,s at the rear..also check your intake pipes from throttle body to intercooler..they can become loose at the trottle body cos there only held in with 1 lug which can break easily..

[derdle]

"Charge pressure maximum etc..." Turbo over-pressure is a classic fault thrown by a boost leak somewhere. So somewhere after the turbos and before the engine the pressurised gases are escaping. You can clear the fault with Vagcom to restore normal operation, but the fault will re-appear at some point until you rectify.

A pressure test should show you where the pipes etc are leaking. Not sure where you are, but many tuners in England can do a pressure test for you.

HTH

Paul

[Enne&Effe]

My mechanic has done the pressure test and changed 1 DV pipe that was slightly leaking, but he didn't find other leaks.
He also changed the N75 valve and both DVs (putting the original ones instead of the Forge I was using).
After the replacement the car was a lot better (before the car couldn't overcome 3k rpm without going in limp mode.....), but the problem still remains......

But why, if I disconnect the MAF, the idle revs become perfect?
If there is an air leak the problem should remain even with MAF disconnected, shouldn't it?