weird idling

[screwdgie]

When I am crusing to a stop in neutral, the rpms will go up to 1500 then drop to 1000 and back and forth until i come to a complete stop. It only does it when rolling to a stop. Anyone know what this might be?

 

[RiceKiller_TSi]

Boost leak at the throttle body seals or ISC motor going bad.

 

[Alibi]

Boost leak at the throttle body seals or ISC motor going bad.

+1

But the ISC would do it all the time.

 

[Livid]

Not neccessarily at the TB. I've had the same problem, and it turned out to be a crack in my downpipe, the leak can be anywhere from that point up, could also just be a matter of getting it tuned, but most likely a leak.

 

[RiceKiller_TSi]

I've never heard of a leak "after" the combustion cycle causing idle probs before. Partly because the problem is caused by the air metering being off due to the leak before combustion causing a rich condition at idle.

But true, the leak could technically be anywhere in the intake tract. Test for leaks.

 

[Gillespie]

I've never heard of a leak "after" the combustion cycle causing idle probs before. Partly because the problem is caused by the air metering being off due to the leak before combustion causing a rich condition at idle.

An "exhaust" leak in front of the first o2 sensor can also create an idle problem, not only in the intake.

 

[RiceKiller_TSi]

An "exhaust" leak in front of the first o2 sensor can also create an idle problem, not only in the intake.

Interesting. I guess it could. Yep.

 

[screwdgie]

I think i have fixed the problem. I tried adjusting my BISSS screw. The rubber cover that was supposed to be over it wasn't. I tightened it until my idle went down from like 1200 to 750-800. I test drove it and it idled better than ever at a stop and rolling.

Just to see what would happened, i loosened the screw all the way out. The car idle back and forth from 1300-1500. It sounded really nice, like it was cammed. I test drove it like that and ran fine too.