I need to know what the 4.0L OHV idle speed is when warm. I know its higher to begin with. I have been looking all over this forum and the web and nobody says what the RPMs are at idle, in park. Thank you!

 

Desired idle is around 700 RPM

 

my manual 4.0 2011 idles at 750-800 when warm
first start up its higher when its cold maybe as high as 1500 and slowly drops
normal is 700-800 on just about any car
auto trans will drop idle slightly when in gear at a stop

whats up with your idle?

 

-make sure the throttle body is clean
-unplug the IAC
-set the hard stop so the idle speed is 500-550
-reconnect the IAC

this will give you a starting point to determine if the IAC is at fault

 

I'm fresh off of replacing the heads, I've got 40 miles on it since i put it back together. The IAC is brand new, the throttle body is spotless, the MAF is clean, the throttle cable is fine, all gaskets and seals are new/fine, and there doesn't appear to be any vacuum leaks. No check engine codes either. It idles about 1000 when warm. It was running like this before the rebuild so i was hoping it would be sorted out when i was done but no such luck. It shifts hard into second as well, and I'm assuming thats because its revving high. Only mods I've done are a K&N kit, screamin' demon coil pack + wires, and full exhaust. Any guesses?

 

vaccum leak check again, confirm vacume with guage. (you probably already did)
Only thing i could sudgest after is possible reprogram if you know someone with a tuner and or just for giggles try the hard reboot with disconnecting the + and - for like a half hour
Good luck

 

yeah, definitely sounds like extra air is getting in the mix and revving up

 

Ill double check for a vacuum leak. I have no idea where it would be, i was extremely meticulous about all the seals and i even replaced any dry rotted hosing.

 

What is the base idle with the IAC unplugged?

 

Ill try that tomorrow and get a number

 

Ok, when i unplug the IAC the idle drops to where it should be, about 800 RPMs.

 

Then your IAC is bad.
I remember you saying that you replaced it?
New parts go bad too.

 

Yeah, got it from Auto Zone

 

I had this problem with my 3.0L and i found out it was a combo of the IAC and throttle body position sensor if im not mistaken.

 

800 is too high with the IAC unplugged. It should be 500-550. If the throttle body is clean, set the idle to 500-550, disconnect the battery for 30 mins with the headlight switch on (to clear the keep alive memory in the PCM) and see if it is better. If the idle is still too high when the IAC is connected, the TP sensor voltage may be too high at idle (over 1 volt).

If there is a 1% chance you have a vacuum leak, all of this does not apply.

 

I have not replaced the throttle position sensor. Could that be causing the problem as sickranger3.0 stated? Toreador 4x4, how do i set the idle? The stop screw on the TB? Also, where are some common places a vacuum leak would occur?

 

If the throttle position sensor voltage is too high at idle, this can cause a high idle condition. The TP voltage should be 0.9-0.99 volts at idle.

The base idle speed will be set by using the throttle stop screw, the screw that everyone says not to adjust.

If the motor was just apart, you could have an intake gasket leak, throttle body gasket leak, a vacuum line for the EGR, EVAP, heater etc that was not reconnected etc.

 

EVAP would throw the check engine light wouldn't it? And someone mentioned to me there was a base idle reset procedure?

 

Bringing this thread back to life, had some crap going on so I haven't had time to fiddle with the truck, but a friend brought up an interesting point; Is it possible that the engine is revving high to compensate for all of the improved airflow from the CAI and full high-flow exhaust?

 

Nope.
Engine dosen't know or care what the exhaust is, or how it gets air.

 

Long shot, I know. I'm running out of ideas.