hot start up idle problems

What JT said is good

Heck when is it that he puts up stuff that is not good ... NEVER :Word:

The idle on a Stang is controlled by
tb stop screw
tb bleed screw
iac
spark
O2's
and
all kinds of info contained in the pcm

So ... there are many ways to skin that cat

btw ... all the above just applies to a STOCK Stang

If you got mods ...
some OR all of the above ...
can be thrown outta whack

The iac just basically tries to compensate for mechanical load being placed upon the motor such as ac compressor and the like.

Heck Fire ... you even have the pcm boosting the injector's pulse width when
you got a heavy drain on the battery

You can adjust your idle like JT where the iac doesn't come into play at all
or
a good bit
or
somewhere in between.

The thing that can be so is if your mods have hosed the pcm values to
the point that ... NO MECHANICAL ADJUSTMENT ... is gonna help.

Getting back on track here
If the iac is not working properly ... it can cause you some grief

Grady

mustanggt94 said:

Just want to clear things up a bit...what do you mean by "DC?"

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Not stupid at all. Duty Cycle. Our IAC's use PWM (Pulse width Modulation). Rather than having a fixed displacement restriction, the pintle flutters.

Mr Grady just shotgunned us with all the things that control this stuff (I didnt know about the injectors spewing under a big load. Makes sense. ). That just kinda shows that someone might have to try a method or two to find what works. As Herr Grady said, each case needs to be evaluated individually (much like fox idle surging).

BTW, Grady let's talk about who is never wrong. You! There was that one time way back when. Remember, everyone said you were wrong. But then science later found that you were right afterall and everyone else was wrong.

Do you guys think that the IAC is gonna cure all my problems or am I still gonna have something else trying my patience. I think the IAC is gonna help but I don't think it will fix all my problems. Hissin50 you said that a bad IAC could cause a hesitation when cold I'm just curious how this could affect the throttle response? Also could it cause hesitation during hot starts as well?

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That's kind of a toughie. As you've seen from Grady, there are myriad variables. If your IAC isn't used much at hot idle (like mine), we can have an ineffective IAC and it's less apparent.

I dont see a bad IAC affecting throttle response much at all, and certainly not once you are over 1500 RPM or so. If you have the throttle response issue when the motor is hot, the IAC is even less likely [the main issue] IMHO.

On a side note I can't wait to get the tweecer R/T. I downloaded the software and j4j1bin earlier today just so I could understand better some of the things talked about in the tuning forums. After looking at the base spark table I can see why everyone says the cobra tune is so conservative. With the lower load spark values being so high and the WOT row timing being so low it seems that twisting the dizzy could cause ping under lower loads yet still not be evan close at WOT. Maybe that makes sense

Click to expand...

You hit the nail on the head. As counterintuitive as it can be, when pinging under low load, it can help to stand on the gas.

If I disconnect my IAC while the engine's idling, it immediately dies and then it won't start up again hot or cold. I think that's a sure sign of a properly functioning IAC, therefore a total IAC failure would cause a stall and no start situation. A partial IAC failure might cause stalling with the engine able to restart albeit with difficulty.
Hot starting problems are more likely to be caused by an electrical item that's sensitive to heat soak e.g. ignition module, coil, PIP sensor.

Wow.