High Idle

[glh-s-car-go]

Car is an 86 GLHS with a mostly stock motor,added BOV and cone filter.

It has a high idle. Really high idle. About 3k rpm. It all started when out at Willow Springs(The Big Track). I came in cause it was running a little hot and I could hear the valves clatter(lifter rattle). As I came into the pits the car was running at 4500rpm and settled down to 3500, then 3000 after a little bit. I pulled codes and got #15 (speed sensor). Let the car completely cool and looked around, then started it back up and still idling at 3k.

I have checked for vacuum leaks and I can't find but I seems to me that I can hear one. I don't think its from the cone filter, never did that before.

I have checked the IAS motor and it was ok. Any ideas? Could a leaking EGR cause this? I'm at a loss. Over 3k the car runs great, no power problems.
Help!!!

[toddipoo]

You have a vacume leak.
CHeck all the plastic lines that come off of the little vacume thing because when they get old they crack. That will make your idle 3000rpms.
As for code 15.
Check the little plastic sensor thing just above the front axle on the driver side part of the car. Sometimes they come loose and they just plain break.

Hope this helps

-toddi

[toddipoo]

Is your motor a Blow through or a SUck through?
If you added a BOV to a suck through its pointless and that might be the problem. Adding the Cone filter will make a loud sucking noise coming from your intake If it is a suck through If not then it is still normal because you can now hear the turbo sucking air in.

I would check the vacume lines again because an idle at 3000rpm's is almost always a vacume leak.

-toddi

[CSX321]

The S/D sensor code is because of the high idle. The computer sees that the engine is not at idle rpms for an extended time, the throttle is not open very much, and it doesn't see any pulses from the S/D sensor, so it assumes the sensor must be bad. But really you're just not moving.

If you can hear more clacking noise now, maybe you've got a leak or hole in your intake/exhaust gasket.

[glh-s-car-go]

I wasn't sure how big of a vacuum leak I needed to cause such high rpms, But I will check the plastic vacuum harness again. Or maybe just replace it all with silicone hose.

The car is definately a blow through. And the lifter rattle is the noise I heard. It happens whenever I run hard for awile when its hot out.

[glh-s-car-go]

So I went out a replaced all the vacuum lines for nothing. After I finished, I started the car up and boom, 3k idle. Some more searching around and I found the 4 into 1 vacuum piece cracked. At least I found the problem.

[V8GremlinX]

good luck with that, with my 90 Shadow u can't get that part anymore, so u will have to fab something up, thats what i did
Rich