GM TBI Idle Set Screw

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Jan 10, 2005
Belmont, NC
Anyone with a GM 4.3 TBI kit out there that had to drill out the cover on the idle set screw? I am not getting a good idle (sporatic and too slow). Normally you don't have to change these - this the metal plug, but I do see where you have to adjust them if you make a major engine modification. Going from a GM 4.3 V-6 to the 2F tractor motor probably qualifies :)

I have done this conversion, and it runs great... no idle problems after having the chip tuned properly. Seems like that might be a better place to start. Before re-programming the EPROM, my idle was rough, but probably not too slow.

- Matt
GB TBI Idle screw adjustment

I have done this many times. You HAVE to adjust the BASE idle by turning the "screw" for most GM TBI's (not HOLLEY) there is an torx if I remember correctly. At any rate, that cover is SUPER SUPER HARD metal...I couldn't hardly drill it! I would do it OFF the truck before mounting it if I were you.

If you need tuning help/insructions, PM me.

Good luck.
What about the IAC?

Thanks for the replies. I am pretty confident on my EPROM, but don't feel too solid about the TBI itself. I am going to try and get another donor TBI tomorrow and will drill out the set screw plug before installing it.

BTW, I just pulled the IAC. There is a pretty weak spring on the shaft, but nothing seems to move. Should this valve/jet move in/out with the spring? If so, this may be my problem...

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