Anit-afterburn question
 

I've been having problems with my idle and every sensor I've checked appears ok. It looks like the ISC is ok at least with the ohms. Its reading 12.3. I attempted to clean it with carb cleaner but I am not sure if just spraying some in there is enough or not. But according to page F-134 of the workshop manual I should be able to disconnect the ISC connector and then increase engine speed to 4k. Well once its disconnected the car stalls. Is this normal? I am guessing not but the manual doesn't say anything about if the car stalls it needs replaced or anything else for that matter.


Thanks for your help.

if you disconnect the isc, your car should beable to idle, mines does at least...

On more thing to add that might help in my overall problem is that when it goes into its idleing fit it is running pretty rich. Almost as bad as the MAP sensor being disconnected(the smell) but I've checked it out and it appears fine. So if the car should idle with the ISC disconnected then I guess I should be looking for a new one... :(

The car should NOT idle with the ISC disconnected unless you crank the air bypass valve (on the bottom of the TB) WAY open.

A normal ISC and ABV opening (only 1/4 turn open) should result in the engine dying right after you disconnect the ISC.

Do this:

Adjust throttle set screw to it is backed off entirely.
Adjust ABV to 1/4 turn open.

Reset PFC and perform idle calibration again.

I've actually adjusted those sections yesterday. The TPS is within operating parameters as well. I wonder if this is what happens with a sticky ISC?

I guess if backing the ABV out I can get the car to idle without the ISC connected then I should be able to tell if that is the problem since it shouldn't happen. I'll go try that.

arutha, I think you have the same problem as I do. The ISC sticks slightly open and results in a higher than normal idle speed. On my car the effect is most noticeable with the A/C turned off because the RPM often fails to drop all the way back down to normal. It like the ISC sticks at the very spot needed to hold the correct idle with the A/C is running. When it sticks and the A/C's off my idle will be ~1,100 RPM.

I too have tested all the sensors, adjusted the throttle plate, verified the TPS, and etc. I've had the ISC off where I actually saw it stuck slightly open. But once it cooled off completely it never stuck again during my bench testing. I cleaned it out with carb cleaner and re-installed. It worked correctly for about 5-10 minutes, but once the engine reached normal operating temperature again the sticking came back.

Also my car has the tendency for a slight over-rev during normal driving up-shifts. The engine RPM will increase several hundred RPM, almost as if the driver is new to shifting a manual.

I tried disconnecting the wires to the ISC and adjusting the idle bleed screw enough to keep the engine running, then went for an extended drive. All the bad behavior was completely gone. While disconnected my idle was down about 600 RPM, which was OK for testing, but if I attempted to turn the steering wheel while stopped, the engine would stall because the ISC wasn't there to automatically increase the RPM. As soon as I re-connected it all the bad stuff came right back immediately.

My previous post should have been IAC not ISC.

Yes. That is the correct way to rule out the ISC. Open the ABV a few turns open. Disconnect ISC and start car. Then adjust ISC so idle is about 900 rpm.

You can put the commander on the dash or out the window and into the engine bay as well, to help with this :)

can the ABV be totalled closed and the idle set only by the idle adjust screw in the front of the TB? Then the IAC could adjust for variances like A/C and PS?

what is the point of having the ABV? Any disadvantages to blocking it off?