bluepayphone

I have a 2008 GTS w/ manual trans and it's been having idling problems. It idles fine for 5-10 minutes and then it starts to RPM jump. It normally idles around 700-750 where it should, but then start to jump up to 1000-1500 every few seconds, then it'll even out for a few seconds and jump again. Sometimes when I'm coming to a stop and put it in neutral it will also stick at 2000 RPMs.

There seemed to be an air leak at the TB and replaced the TB gasket with no solution. Now I don't know what it could be, it's acting like its a vacuum leak, but I don't know if it might be the TB controller itself.

Does anyone have any ideas?

Also, no codes are showing up.

dirkka

I would like to know this too. Other people have posted this same problem, but with CVT models so I thought before this was strictly with those models and not manuals

bluepayphone

Just a little update, I cleaned the EGR valve and replaced the gasket. No fix. Hooked it up for live data, when the idle jumps/drops it's going from CL to OL, but still not throwing any codes. I'm thinking maybe a bad thermostat, temp sensor, or something in the EVAP system? But my thoughts are that those would give me codes.. Any ideas where to start would be appreciated.

CamShaft

If you suspect a vacuum leak, get a can of ether and spray it around the intake. If the RPM jumps all of a sudden, then that's the area you have a leak.

But, you could have other thing causing the issue too, as you said the emissions system is going from closed loop to open loop. I am not sure how the EGR works on this car because I don't have it. Here is some info from the manual.

bluepayphone

Update:
I ended up having to take it to the dealer unfortunately. I guess it wasn't a vacuum problem. Apparently there was a computer issue; said they found a service bulletin about a "hanging idle". They re-flashed the ecu and it seems to be fine now.