I have a manual 2001 VW Jetta. Yesterday I noticed that whenever I'm in neutral, whether i'm at a light or coasting, the RPMs drop to about 500, then shoot up to 1600, then settle at about 1000. When it drops down to ~500, the car shakes a bit as if it's about to stall out, but then it seems to "correct" itself by shooting up to 1600. This happens in a cycle, making my car "shake" about every 5-6 seconds! It hasn't stalled yet when it does that, but it seems so close to stalling that when i'm at a light i keep my foot on the gas pedal lightly to avoid it!

Any ideas what might be wrong? I tried looking online and found some that had problems with overheating and air intake systems (i forgot to look at the temp gauge).

Thanks.

2/10/2008 9:36:29 AM

Sounds like a vacuum leak

2/10/2008 11:57:47 AM

cut it off at stoplights.

2/10/2008 12:15:53 PM

Idle air control valve

[Edited on February 11, 2008 at 5:43 AM. Reason : air]

2/11/2008 5:42:24 AM

do you think that's an expensive fix?

2/11/2008 8:05:41 AM

sounds like a vacuum leak

look for leaks in your intake piping. it's easy and free

2/11/2008 8:21:19 AM

get a propane torch, start the car and turn on the torch but do not light it. move the nozzle of the torch around vacuum hoses and seams in the intake. If idle increases when in a certain area, you can narrow down the leaking area. It will be hard if the idle is not constant like you are describing, but you can figure it out.

2/11/2008 1:13:29 PM

my dad looked at it trying to find a leak but couldn't find one. And....i don't have a propane torch.

2/11/2008 3:16:33 PM

http://www.2carpros.com/topics/iacvalve.htm

2/12/2008 5:52:42 AM

^ what he said. it could also be something as stupid as a dirty fuel filter or dirty injectors. or it could be a bad crankshaft or camshaft position sensor

[Edited on February 13, 2008 at 8:06 AM. Reason : .]

2/13/2008 8:00:31 AM

so it hasn't happened since sunday when it was really bad - should i just wait it out til it happens again or take it in before it starts to stall out on me? I'm just afraid that i'll take it in and tell them what happens, and then it won't do it when they look at it (this happened when i showed my dad)

Thanks for the tips

2/13/2008 8:23:36 AM

wait a minute. Could you have a bad tank of gas?

2/13/2008 7:04:30 PM

probably not....it's happened before, but nothing like it did on sunday. but good thinking

2/13/2008 7:19:42 PM

so it got pretty bad - check engine light came on, near stalling and shaking continued. Brought it to the dealer and spent $300 bucks (on my birthday of all days) on a "speed sensor". My receipt said "multiple faults for misfires, cam position, and engine speed sensor". Also, they fixed my ECT sensor which was under recall this past month.

Hey, but I got a "free" carwash and courtesy tire/brake inspection out of it.....

3/4/2008 11:01:53 AM

so, i was right?

3/13/2008 10:02:07 AM

is optprimuses response helpful or bullshit? i'm guessing bullshit

3/13/2008 10:06:32 AM