sstang

I just installed an MAC 75mm TB and PP plenum and now my Idle Air Control Valve seems to be acting up. I had no problems with it before the swap. Now it makes my car idle a couple hundred rpm's higher, and my car wants to hang rpm's real bad. With the sensor disconnected the car runs perfectly. For now is it any problem to just run the car with it disconnected? It gives me a CEL but I see no ill effects and the car actually runs right that way.

I have seen the trick to making the IACV gasket hole smaller so I may try that eventually.

gone to 7734

If you learn anything let me know. Mine is doing the samething accept higher idle I have a thread going RPMS slow to come down.

Sxynerd

He has the same problem as you 7734.

Any time you adjust the back pressure or the o2 amount into the engine the IAC is going to respond differently than it did before. Anything from better flowing heads like you 7734 to and Mac TB and YES even a O/R H pipe will screw with the IAC. THere is a few different things to try. Normally I just tell people to do the IAC mod till they can get the car tuned.

I did forget to mention to disconnect the battery for a period of time also, to reset the ALM. Some Air problems are less of a problem and the ALM can adjust.

sstang

Yeah I did reset the battery when I did it. I just thought it was weird since I put the exact same TB/plenum set up on my bro's '00 GT and it didnt have any problems. But for now the IAC is disconnected and it runs perfect. I will do the IAC mod soon though.

And I was suprised how much harder the wheels spin from the TB/plenum!

cliffyk

Here is the procedure for setting the throttle valve stop screw (aka "idle screw", which it really isn't) back to the base setting, and how to tweak it if the idle is still not right...

defconfire

I had to turn my up like 5 full turns. So it wouldn't stall when coming to a stop.

cliffyk

Curious, was that 5 turns from the base setting as set by the procedure, or 5 turns from where the TB cam from whomever made it? I have never had to go that far, even on some radically cammed engines...

sstang

cliffyk, I tried messing with the idle screw but it is already back as far as it will go so the TB closes fully. I have no problem with low idle, it idles high, but I know it is completely having to do with the IACV.

Another problem I'm having, the MAC throttle body has a hard spot at the beginning of the gas pedal. You have to use a little force to get the pedal to start to move, which usually results in rpm's flying up, so its a little hard to take off smoothly. Has anyone remedied this problem before?

defconfire

If you slightly crack the TB using the set screw you wont have problems with it sticking.


IMHO it sounds like your car needs to adapt. If you disconnect your battery and let the KAM reset, then just drive the car it should adapt to the new setup.

sstang

Okay I will try using the set screw to keep it cracked, but hopefully it won't idle too high and can still be past the hard spot. I'll try that thanks.

And the car was reset and I put some miles on it but it wasnt changing.