idle problem

[nerraw117]

I set my idle to around 1k by the idle set screw on my tbi. I also adjusted the throttle position voltage. after a hard day wheeling; after 20 seconds are so idleing my idle starts dropping to 500 or so. then it misses and floats from 500-800. any ideas? it has a new IAC also.

btw I just noticed my membership ran out. got to renew it.

 

[dyeager535]

EFI doesn't adapt to mechanical idle changes. Needs to be set to factory to work right. Any changes to idle need done through tuning, or manipulation of the throttle.

Sucks, but EFI has a target idle it tries to achieve, and uses the IAC to try and get there. Opening or closing the throttle too far messes with it trying to reach it's target RPM.

 

[nerraw117]

what is the target rpm for a manual? 800? my ecm is from an auto and it was 600 i think. (way too low for a manual)

 

[dyeager535]

I believe you are right. It may vary somewhat based on the particular GVWR or year, but 800 is in the ballpark as I recall. Autos were somewhere near 550 in gear.

What happens with the idle too low? Is it just near impossible to let the clutch out without using the throttle?

 

[k20]

Is it just near impossible to let the clutch out without using the throttle?

Yeh thats the problem hes having, going to put a hand throttle on it, but another guy we know says if he locks his hand throttle on at say 1k rpm, and lets it hold there for awhile, the computer starts freaking out and causes it to (I cant remember which) either continue increasing rpm, or it starts to revert back to the stock idle speed.

 

[nerraw117]

even with the idle at 1k it still will die if I do not give it gas but it is much much better with a higher idle than 550.

 

[dyeager535]

Does it stall with the trans in "low" too? You've got another problem if it won't walk out in low or 1st with reasonable gears.

 

[nerraw117]

sometimes and sometimes not. If it doesnt stall if it gets on any hill it will die. i run 4.56's and 38's.