IAC problem?
 

I have a 99 GT with a VT Sportsman motor, VT Stage II cams and most of the bolt ons. My car is tuned by Steeda.ca with a SCT chip.

The car ran perfectly when I got it back, but then a problem started a few weeks later.

The car starts fine for the most part but when depressing the clutch and coming to a stop in neutral the car stalls. Not all the time, just sometimes. The idle tends to hunt a lot more too.

Other times, the car runs great. Not even a hiccup.

Sometimes, the car doesn't like to start very well. It takes 10+ seconds to get it started.

Is this an IAC problem?

The IAC may be the stalling issue but I doubt it's connected to poor starting. I would start off by cleaning your cable connections both at the battery and at the engine, the way top terminal batteries cause corrosion your always best to clean em pretty regularly. If that checks out ok you might wanna have Paul run it while hooked to the scanner to confirm all sensors are working properly.
I will however ad that several folks report periodic poor starting with 4.6's. Yesterday when Raf was over his car required 2 or 3 goes at the key to bring it to life, he said it's an off and on problem.............mine isn't as bad as that but does require a second turn of the key at times.

Paul's been all over this car and tuned it a couple times. I will check the terminals over the week-end. Thanks

My only other suggestion would be to clean both the IAC motor and MAF.

Sounds like the maf transfer function could be rich in the lower end of the curve... It could be learning the wrong correction as well, due to an o2 sensor problem or a exhuast leak.
Another area of the program to look at is the dashpot settings.
All the above must be changed in the program/tuner.
Disconnect the battery and wait a couple minutes to clear the KAM. If the issue goes away, but comes back after a couple weeks, its definately a tune/sensor related issue.
.02
Matt

I plan on changing the o2's as well as the IAC in the coming weeks.

Paul from Steeda.ca recommended I change my O2's. I was just hoping that perhaps it was a cheaper fix than $200 pair of sensors :)

Tonight I took the IAC off. Would a mis-aligned gasket cause this? The gasket was covering at least 1/3 of the hole.

I cleaned the IAC and aligned the gasget properly and put the IAC back on. I disconnected the battery and will fire it up tomorrow and see if any of that made a difference.

More than possible, you'll know better tomorrow after driving it for a bit.
Fingers crossed for you.

Well, the culprit was the IAC. She runs just fine, doesn't hunt one bit and idles right about 1k. Now I can get back to enjoying the car ::biggrin:

Gotta get lucky sometimes............ :tup :tup :tup

My car has some hard starting issues as well. It is periodically that the car will not start until the second or third try. I find that if i turn the key and let it sit for 5-10 seconds until the radio kicks on(stock mach amps power up) that the car starts pretty well every time. If i just turn the car over with no delay it may not start well. I really wish I knew why the car started hard sometimes.

Have you checked the basics like.........
-clean all connections at the battery
-clean the body ground
-clean connections at the starter
-had the battery checked (they can sometimes have lots of amps to roll the starter over while the voltage has dropped low enough that the ECM will not properly function)
-fuel filter (has it been awhile??)
-plugs (old or maybe have the wrong ones in there?)
Many times it's the simple things that cause that kind of issue.

After doing tons of research about my problem, a gummed up IAC is a very common cause of a hard start. Take it off, it's just two 8mm bolts and clean it inside with some carb/TB cleaner. While you're at it, disconnect the battery and reconnect it once the IAC is cleaned and back installed so that it resets the KAM memory. :tup

Another tip to help those with rough idle would be to check vaccum lines they can cause havoc.

Cheers :cheers: