Anyone know (no guessing please) the syptoms of a bad idle stabilizer valve. Once my car drops back to idle, the engine rpm fluctuates form 900-1500. I have the idle set pretty high, it is a race motor and I like the idle around 1500.

It will hold 1500 rpm for a few seconds and then drop to 900 and return to 1500. The time between dips varies from every few seconds to 10 seconds or so.

Thanks

 

Mine was doing exactly that when I had a vacuum leak and a sticky ISV. Even with the vacuum cleaned up the ISV was still sticking. Spray some WD40 into the hose for the ISV, it may help clean it up. If not, delete it (or replace it). That is provided you dont have vacuum leaks.

 

I dont have nay vac leaks but how do you delete it and are there any cons to it...

 

If I decide to disconnect the ISV do I plug both ends (manifold/IC pipe) or do I run an open hose between them.

 

I plugged both ends. The disadvantage being that you have to use the gas to keep your car idling till it warms up.

 

You can test the ISV by bypassing it electrically.
Jumper points B & C on the diagnostic plug in front of the firewall on the driver-side fender (has black cover).

Refer to Clark's procedure (www.clarks-garage.com) for 'idle adjustment' as it requires bypassing the ISV to set the idle and shows a diagram of the plug.

After jumpering the diagnostic plug, if your idle smooths out it is likely the ISV. You can leave the ISV bypassed if you want. Only downside is having to feed it gas when it's cold. I just did this on my car and it isn't a big deal. Beats $150 for a new one.

Alternatively, your O2 sensor may be dieing.

 

You need to set the idle back to spec.

When the engine is at idle (throttle plate closed) the throttle closed switch in the TPS is closed and sends a ground to the DME. When the DME sees this ground signal and the engine RPM is above a pre-set value, the DME assumes the engine is in a Trailing Throttle or Over Run condition.

To improve fuel economy and reduce emissions the DME is programmed to turn the injectors off during Trailing Throttle condidtions.

So, with a high idle the DME turns the injectors off, engine RPM drops, the DME turns the injectors on, RPM rises, and the cycle repeats.