Demon33
10+ Year Contributor
- 296
- 2
- Aug 11, 2008
-
Southern,
California
I recently replaced my ISC and now I'm dealing with idle surge. I've looked up all the usual suspects and have done most if not all without success.
So, I was thinking about it some and thought maybe the new ISC is the culprit. What I'd like to know is how can one determine if the ISC is actually seating properly, sealing the air bypassing the throttle plate and reducing the idle? For instance, if my logger is showing 0 for ISC position, how can I be sure it's actually at the 0 position and not some other partially open position which would allow air past the throttle plate increasing the idle when I actually need to reduce the idle?
I currently have the FIAV blocked, my TPS reads 10.1% at idle, no boost leaks and the BISS has no affect on idle! Idle seems normal during warmup and begins to surge between 800-1500 rpm as the coolant temps rise to normal. Wideband reads full lean during surge, EGT is extremely cold at about 300C (minimum reading on gauge) and injector duty cycle fluctuates from 0% to 2.3% as the engine surges. Disconnecting the idle switch, the rpm settles and holds at 1500 rpm. Reconnecting the switch brings the surge back.
Again, how can I be certain the ISC is fully closed when my logger reads 0 for ISC position?
So, I was thinking about it some and thought maybe the new ISC is the culprit. What I'd like to know is how can one determine if the ISC is actually seating properly, sealing the air bypassing the throttle plate and reducing the idle? For instance, if my logger is showing 0 for ISC position, how can I be sure it's actually at the 0 position and not some other partially open position which would allow air past the throttle plate increasing the idle when I actually need to reduce the idle?
I currently have the FIAV blocked, my TPS reads 10.1% at idle, no boost leaks and the BISS has no affect on idle! Idle seems normal during warmup and begins to surge between 800-1500 rpm as the coolant temps rise to normal. Wideband reads full lean during surge, EGT is extremely cold at about 300C (minimum reading on gauge) and injector duty cycle fluctuates from 0% to 2.3% as the engine surges. Disconnecting the idle switch, the rpm settles and holds at 1500 rpm. Reconnecting the switch brings the surge back.
Again, how can I be certain the ISC is fully closed when my logger reads 0 for ISC position?
