High Idle, cannot find cause

[chrisfullwood]

I have a High Idle Question. i got a new 91 Eprom ECU with a stage 3 chip, the idle set to 850,
well i installed it, pretty much right away the idle was at 1450 or so... i figured my ISC was going out.. i tested it, and it was borderline bad... so i ordered a replacement (which took a while, and while i was waiting the idle ended up over 2000), well i replaced the ISC, no difference... in the end, realised that the isc cant do anything about an idle that high, so i took all the IC pipes, off, found some leaks, fixed them... new gaskets on a few places that air was escaping...

still no improvement.... i have a small boost leak, 10psi or higher.. vacuum is a solid -20 (i guess its negative.. but on the negative side of the boost gauge) it has been since i built the motor.

i cannot for the life of me figure out why the idle is so high, before the winter it was fine, it idled perfectly at 900... after the winter, its acted up constantly.

any ideas would be awesome, ive combed through various DSM sites, and i cannot figure out what it is...
by the way the car is a 90 Galant GSX with a 91 Turbo Galant Engine, with stage 3 chip, and Eprom ECU
theres is no EGR, there is no Boost control solenoids, or FPR solenoids.

 

[64_Frankenstein]

I have a High Idle Question. i got a new 91 Eprom ECU with a stage 3 chip, the idle set to 850,
well i installed it, pretty much right away the idle was at 1450 or so... i figured my ISC was going out.. i tested it, and it was borderline bad... so i ordered a replacement (which took a while, and while i was waiting the idle ended up over 2000), well i replaced the ISC, no difference... in the end, realised that the isc cant do anything about an idle that high, so i took all the IC pipes, off, found some leaks, fixed them... new gaskets on a few places that air was escaping...

still no improvement.... i have a small boost leak, 10psi or higher.. vacuum is a solid -20 (i guess its negative.. but on the negative side of the boost gauge) it has been since i built the motor.

i cannot for the life of me figure out why the idle is so high, before the winter it was fine, it idled perfectly at 900... after the winter, its acted up constantly.

any ideas would be awesome, ive combed through various DSM sites, and i cannot figure out what it is...
by the way the car is a 90 Galant GSX with a 91 Turbo Galant Engine, with stage 3 chip, and Eprom ECU
theres is no EGR, there is no Boost control solenoids, or FPR solenoids.

Hmm that sounds kinda werid. I don't know much about EPROM ECU. Have you check the ISC motor wiring harness? That happen to me before.

 

[chrisfullwood]

yeah i checked all that stuff... the only other thing i can think of is the timing somehow is totally out... but shouldnt that be set with the new ECU? could the position of the CAS be messing with the timing for the new ECU, i wonder.

and to show how much good luck i have, the shroud with the timing marks is broken off of my engine (before i got it...) so i relied on my logger, which also broke this winter.... awesome huh.

 

[yokotabrat]

Unfortunately, the timing numbers the logger will read won't tell you what the base timing is. The base timing in the ecu is always assumed to be 5 degrees BTDC, so you'll have to fix your timing cover to know for sure what it's set for.

Have you tried blocking the FIAV? Was the ISC that you had lower in resistance than the good one? If so, it's possible it's damaged the ecu. Is the throttle being held open at all? Have you checked to see if the idle switch is functioning properly according to the logger?

 

[andy4g63]

Check the idle switch, as Bert stated, measure again the ISC with ommeter, check for possible leaks on and around TB/gaskets, seals,etc./. Make sure the TB is closed, when car idles.