My truck was not starting sometimes so I replaced the IAC and the problem went away, now it's kind of showing the same symptons. Can a dirty throttle body cause the IAC to get dirty in that short of time? any thoughts guys? Thank-you.

 

Yes, not as bad but it's well worth cleaning.

 

If it wasnt cleaned properly, could go bad again shortly after. Use wd 40, it is safe on rubber compounds. There are rubber seals in the IAC. Plus it helps lubricate the plunger. I've cleaned them before with carb cleaner and had issues later on. Also is a good idea to make sure the plunger is working freely.

 

Here is a little more on the issue.
The throttle plate's stop is adjusted so the plate is open a small amount to allow air to pass as a 'Minimum amount of air' the engine should idle on at a low idle in the 500 rpm range without the IAC being open.
The IAC normally adds extra air to bring the idle up to the 750 +/- range.
With this setup, the IAC now has operating room to keep the idle close, by modulating the bypass pintel under control of the PCM.
So, if the throttle plate has gum build up, the IAC does not have the base amount of air to work with from the throttle plate's small amount of opening.
The PCM uses the crank sensor to tell what the idle rpm is and modulates the IAC to hunt for the correct idle speed as set forth in a software table looking for a match.
Often what happens over a period of time is the PCM tries to correct the condition by shifting the idle table.
When this happens and the repair is made, the PCM still has the last operating history. What you do then is reboot the PCM by removing battery for about 5 minutes so the PCM starts from unaltered tables and relearns the correct idle control.
There is even a procedure to help shorten relearning time because a number of things depend on idle control to be good and precision under all operating conditions.
Good luck.

 

I think Bluegrass just said in so many words that a dirty throttle body CAN affect the idle even with a properly working IAC.

To test that theory, crack the throttle open VERY slightly and see if it starts. If it does, pull the TB and clean it.

 

All I know is my engine runs better when the throttle body is clean. I replaced the IAC with a new one when I cleaned the throttle body. I have seen posts on this site where cleaning the IAC didnt do the trick.. Some times you need a new one. Should clean the throttle body no mater..