Demon33
10+ Year Contributor
- 296
- 2
- Aug 11, 2008
-
Southern,
California
Have any of you fellow 1990 4G63T owners successfully replaced your '90 ISC (with pigtail connector) with the newer version of ISC (without pigtail connector) and didn't experience idle surge? After A LOT of testing and troubleshooting, I'm convinced the new ISC is the source of my current idle surge.
My old ISC wasn't dead but I recently installed a newer ISC in my '90 throttle body in hopes of putting less load on my 20 year-old ISC drivers and hopefully extening their life a little. Since making the change I have been experiencing bad idle surge. In my search for the cause I did a boost leak test and fixed a leaking EGR valve. No other leaks exist, but the surge persists. Base ignition timing is 5 degrees BTDC, BISS and TPS are adjusted properly and idle switch is set and working.
After extending the ISC wires on the harness, I tested the new ISC by plugging it in and turning the key to the ON position and the pintle (tip of ISC) moved out and extended from the ISC and made clicking noises for a bit. The position shown on my logger is about 108. When I turn the key to the OFF position the ISC pintle moves in or retracts a little and the logger shows 90 for the position. As the car warms up, the ISC position begins to move towards 0 (ISC fully retracted) which allows more and more air to bypass the throttle plate. This has the affect or raising the idle RPM which leads to idle suge.
However, tonight when I plugged my old ISC back in and turned the key to ON the pintle retracted which is completely opposite to what the new ISC is doing. When I turned the key to OFF it extended slightly.
I'll probably reinstall the old ISC tomorrow, but I just need you guys to verify whether or not you've been able to use a newer version ISC in place of your '90 ISC without any problems. If you have, my new ISC might be defective or I may have just wasted my money.
My old ISC wasn't dead but I recently installed a newer ISC in my '90 throttle body in hopes of putting less load on my 20 year-old ISC drivers and hopefully extening their life a little. Since making the change I have been experiencing bad idle surge. In my search for the cause I did a boost leak test and fixed a leaking EGR valve. No other leaks exist, but the surge persists. Base ignition timing is 5 degrees BTDC, BISS and TPS are adjusted properly and idle switch is set and working.
After extending the ISC wires on the harness, I tested the new ISC by plugging it in and turning the key to the ON position and the pintle (tip of ISC) moved out and extended from the ISC and made clicking noises for a bit. The position shown on my logger is about 108. When I turn the key to the OFF position the ISC pintle moves in or retracts a little and the logger shows 90 for the position. As the car warms up, the ISC position begins to move towards 0 (ISC fully retracted) which allows more and more air to bypass the throttle plate. This has the affect or raising the idle RPM which leads to idle suge.
However, tonight when I plugged my old ISC back in and turned the key to ON the pintle retracted which is completely opposite to what the new ISC is doing. When I turned the key to OFF it extended slightly.
I'll probably reinstall the old ISC tomorrow, but I just need you guys to verify whether or not you've been able to use a newer version ISC in place of your '90 ISC without any problems. If you have, my new ISC might be defective or I may have just wasted my money.