Sounds too much like a vacuum leak. Very hard to find without smoke. I had one that drove me nuts for a few days. Turned out to be small vacuum line behind the throttle body.
Look at this picture closely. You ca see the plastic line that came out of a hose. Reinstalled and ziptied...Keep looking...you'll find it.

 

Please can you explain how to do this test with the break cleaner?

If the car has a leaknat the vacuum line what I should see?

 

Sounds like a pesky vacume leak somewhere.. I have one driving me crazy.. After I run the abd stop. The idle will jump to 1000 rpms go back down then immediately back up to 1200 rpms then to normal.. Then after a minute it will so it again.. Till I start moving again. When I turn the ac on it drops

 

try to explain with my little english knowledge, if you spray brake cleaner at the intake hoses and you have a vac leak ...your engine breath brake cleaner instead of air and at the moment you find that leak your engine change the idle rpm,


it is possible you have a leak between maf and turbo`s only at the intake side..

you have disconnect the maf and try the idle without maf?
do you checked failure codes and maf sensor output at the moment your failure exists?

 

I use WD40 because brake cleaner can evaporate very fast,,depending where and how far the leak is downstream...
Some also use starting fluid which increases idle speed instead...
Good Luck

 

Hi,

Today I drove the car and did some tests, conclusions:
- with cold starts the idle spikes occur more frequently;
- no problem with hot starts but some times while shifting (for exemple from 3º to 2º gear) when I press the clutch pedal the rpm spike untill 1500rpm and next down to normal (900 rpm);
- did a new test with durametric software and not found erros;
- there aren't differences with A/C on.

With these conclusions should I try to find a vacuum leak?

Thanks,
VS

Thanks,

 

I am having this very same issue. Vshigo...did you find your issue?

Sorry too green horn to PM. :'(

 

vacuum leak at the y pipe and/or tb. re-check em all. assuming the maf is good. idle hunting is always a minor vac leak. unless it's a failing maf. ( or something that hasn't yet happened to me lol )

 

Hi,

I replaced the MAF but the idle still some times unstable (higher -1200rpm).
I have to go to my mechanic to do the vacuum leak test.
This problem only happens sometimes... If it is a vacuum leak why not always happens?

 

1200 seems very high. but i would check or have your tech check ALL the hoses for leaks. it's easy to have a verrryyy minor leak and not know it. i'm pretty sure i had one for almost a year and barely knew it and assumed it was just the bad maf. it turned out to be BOTH! and any code would be a "circuit low maf"

also: check/clean the TB! could be.....

 

Some times the idle rises to 1200/1500 and then down slowly untill normal 900rpm.
I don´t understand why not always happens?
Some times the idle is stable with no problem!!!!!

 

My car also has a wonky idle... I have pulled the throttle body and it was pretty filthy. I cleaned and lubed the gears and such as well as well as cleaned the wipers. I also performed a pressure test from the exit of the air box. I found a loose hard vacuum tube behind the alternator and was able to get a clamp on it. Also, the left hose out of the turbo was oily and dirty and leaking so I cleaned and tightened that. Re-charged again and found the pressure sensor on the intake plenum to be ever so slightly leaking. I'll replace that.

All that made pretty much no difference at all The idle is great when cold and then, when the car is warmed up, it will sit at 1000 for a while and maybe drop to 880 or so. It will then try to rise and fall a few times. Other times it will go directly to 880 and then try to climb and other time it will sit at 880 and stay put.

Super frustrating! I will replace that pressure sensor, but I bet that does nothing.

Are there any good test for the throttle body? How can I rule it out without replacing it?

Thanks,

Franny

 

vaccum leak!!!!!!!!!