2.0 non turbo engine surging at idle?

[Robotech]

I have a 2.0 non turbo that i picked up a few days ago and the engine surges when it is sitting there at idle. I took a video of it here:

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Any idea what causes it? If you put it in drive, the RPM stays high, but it sounds and drives fine.
Thank you my friends
David

 

[Dstarperformance01]

Looks like a vacuum leak. Check pvc valve and all vacuum sources and hoses. Spraying carb/throttle body cleaner or even brake cleaner on hoses to find leak. Idle will change when leak is found with carb/brake/throttle body cleaner.

 

[Robotech]

Could it be the IAC? (idle air control module)?

 

[Dstarperformance01]

Did you find any vacuum leaks? It is possible.

 

[Robotech]

Did you find any vacuum leaks? It is possible.

Haven't looked yet, but I will.

As a side note, it only does this after the engine is warm... which actually might point more to the IAC

 

[PlanZero]

^^^ I'm betting IAC as well. Good thing about an IAC for a 420a is they're pocket parts at the junkyard or super cheap new. I had the exact same thing when I installed a bad IAC on my Tsi.
However, my GF had an RS a while back with a very similar surge, so I immediately assumed IAC but that wasn't it. I replaced IAC, TPS (actually the whole TB), vacuum lines, etc. but never found the culprit before the car was totaled, so please post a follow up on this as I would like to know.

 

[my1st2genGSX]

Watching the video it looks like the IAC.. Check for leaks.

 

[Robotech]

^^^ I'm betting IAC as well. Good thing about an IAC for a 420a is they're pocket parts at the junkyard or super cheap new. I had the exact same thing when I installed a bad IAC on my Tsi.
However, my GF had an RS a while back with a very similar surge, so I immediately assumed IAC but that wasn't it. I replaced IAC, TPS (actually the whole TB), vacuum lines, etc. but never found the culprit before the car was totaled, so please post a follow up on this as I would like to know.

This is a 2.0l naturally aspirated not the 420, but I'll see if I can't unstuck it first and then if I need to replace it and check for vacum leaks. Thanks guys

 

[PlanZero]

Ohhh. Well I'm sure you know how to test it now. One time I found the voltage was correct so I pulled it, cleaned all the crud off, plugged it in and watched the pintle extend in the key on position and it worked fine. Probably just sticking as you said.
Ironically I bought a new standard brand IAC and it didn't work out of the box.