IAC drill mod Q's
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
you do this to correct idle issues often associated with aftermarket TB's, especially with head/cam
you do not just blindly drill a hole without confirming what your IAC counts are and your TPS volts are
stock size hole in stock TB is 1/8" "most" people doing this have to make the 1/8" hole larger (or first drilling a 1/8" hole in aftermarket TB). You drill in 1/64" incriments as you measure IAC by scan tool each time. "Generally" the hole winds up being 11/64"-13/64" BUT! this is different for each motor
another method is to crack TB blades open slightly and then drill/slot holes in TPS so you can "rack" it back to within correct vdc range.
in either case you need to have a scan tool to read wtf your IAC counts are so you know when to stop "adjusting"
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Opening the TB blades will work if you have a small problem but the trouble with it is your letting idle air into the upper plenum and not routing it through the IAC passages. If you have it open too much you can still get reversion thus creating split BLMs/ fuel trims.
is there a hand held device that plugs in to tell you this information? i beleive My car is OBD1 not 2. I wanted to also get something to tell me knock counts to see if im picking up false knock and its probably useful for the TPS settings.
where can i find one?
where can i find one?
Most any scan tool that displays live data will show you what you want to know. The big name parts stores will let you use them to pull codes but IDK about letting you take them home to use, they may rent them.
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
suggest you start by drilling a 1/8" hole and test. drill 1/64" larger each time and re-test.
Buy a few TB gaskets....you will need them for this on/off/drill the TB deal
IAC max out at 160 IIRC so at 140 you have no room left. when you turn the wheel at a stop and add load to your engine, same as turning on AC, you peg the IAC and the car will want to stall.
Drill mod will resolve this.
when my car is warm the shock of nuetral to drive/reverse will want to kill it lol. Thats why i originally wanted to do this.
So your saying a code reader will also tell me the rest of what i need to know? Just any type?
So your saying a code reader will also tell me the rest of what i need to know? Just any type?
