When I unplug the Idle speed controller the check engine light should come on right? Im trying to figure out why my idle is 1500 and surges to 2000 some times. I unplugged the ISC then started the car, idle droped to about 1400 from the 1500-1600 last time I ran the car, the check engine light did not come on...

Im going to check for vacuum leaks soon, but it will be rainy here for about a week.

 

Are you running the stock computer?

 

yes, stock ecu

 

Not all codes make the CEL come on; some are just thrown and stored in the ECU. Check what codes are stored in the ECU and see if that one is there.

 

hmm ok, ill check for codes.
Thanks

 

I don't think the ecu checks the state of the ISC. It sure sounds like a vacuum leak to me.

 

I did the check for engine codes from http://www.scuderiaciriani.com/rx7/engine_codes.html and came up with nothing

ISC is on the list of engine code things, i think it does check the state of it. Can anyone verify this?
34 Solenoid valve -idle speed control (BAC)

I picked up a can of carb cleaner and I am going to fire it around soon to see if I have a vacuum leak.

 

anyone, know whats wrong?
How can I for sure induce a engine code so I can see if the codes work on my cacr.

 

Disconnect the MAP or Intake Thermo sensors. Either one of those should throw a CEL or at least store a code.

 

Check the TPS adjustment. Even if the car has a vacuum leak, the stock computer should compensate for this, unlike the aftermarket ECU's.

 

tps is solid at .93, that was the first thing i checked. I found a leak at the throttle body to UIM. Im going to clean the gasket and tighten the bolts to 18 ft-lbs and see if that will stop the leak and my problem. Ive checked all my vacuum hoses no problems there but im also getting 10-5-3 boost pattern so I still think there is something wrong there. Ill let everyone know what it was when I figure it out.

 

This may sound dumb, but are you sure the idle control screw isnt adjusted correctly....it may be why the TPS is at .93 and not a tad lower??
Allen

 

All codes are stored, but only codes that affect how well the engine will run will trigger a check engine light. The ISC is not necessary for the car to run - ergo no check engine light. But, if you pull the codes by jumpering TEN and GND, I bet it will be stored.

If you have a high idle, it's one of two things. Either something's misadjusted with your throttle body or you have a vacuum leak after the throttle body. With the car at idle, the throttle plates are totally closed - if this was the only way the engine got air at idle it would stall out. The ISC directs air around the throttle plates to set the idle speed. Same with the accelerated warm up - it brings air around the throttle plates to get the 3000 RPM cold start idle.

That said, if you have something that's keeping your throttle plates from fully closing at idle, or a vacuum leak after the throttle body that's bringing air in around the throttle body, that will bring your idle up. It's that simple. Don't worry about the TPS or the ISC for right now - find out how that extra air is getting in there. Most common is a vacuum leak, which can be tricky to find.

Dale