hIGH IDLING

[93navajo]

Okay I have read all posts on this. My Navajo is idling around 1200 rpm. I changed the TPS as suggested by the search that I have done, cleaned tha MAF filaments, changed the PVC and air filter. It now climbs to 2000 on start up and then drops to around 875. Whats the problem? you ask, well now when I step on the gas pedal and release it, the Rpms stay at 1000 to 1100, and doenst come down. Do I need to reset the cmputer or something or shoud I be looking at something else. I aslo checked the throttle and it does not appear to be stuck. Any suggestions would be appreciated thanks and what a great site by the way. Makes me want to keep this thing. By the way my Navajo has about 158000 miles on it.

 

[88vert]

Have you tried cleaning the IAC vavle?

 

[Bashman]

I would definately reset the computer first.

 

[93navajo]

If reseting the computer is disconectiong the battery for awhile thats what I did. It worked for the first time, the rpms went down to 875 then has kicked itself back up.

 

[Billy177]

check for vaccum leaks

 

[410Fortune]

Step 1. Check for vacuum leaks, look at the vacuum lines, any cracked or broken?
Any missing?

Re-set the computer. Anytime you clean or replace a engine sensor you must disconnect the - battery cable.

If that doesnt work it is likely that your intake manifold has a leak or come loose. This is a large vacuum leak, but it can be fixed. First thing is do those listed above, and see if the high idle returns.

You can also do a proceedure for the 4.0L that will re-set the base idle. But thats part of step 2....

After you re-connect the battery you want to drive the truck around and get it up to temp. A nice calm drive around the neighborhood. this will give the computer an opp to re-learn the new singlas it is getting from the now cleaned or replaced sensors.

 

[93navajo]

I think I did all except for the vacum leak check. I will try that do I just get some soapy h20 and spray on the hoses. I had the valve head covers replaced last winter and the head gasket 3 yrs ago all the hoses look pretty good though. Will try cleaning the IAC, a little more. Thanks again keep up the suggestions please.

 

[Bashman]

An easy way to find vacuum leaks is with a steady flow of propane gas from an unlit torch. As you move the torch around your engine your idle will either increase or smooth out when you hit a leak.

 

[410Fortune]

FYI it is common for the OHV to leak at the intake gaskets.
High idle = vacuum leak (90% of the time)

If the upper intake manifold bolts come loose they can cause this, a temp fix is to tighten them up. A real fix is to replace the gaskets. But it sounds like you had some work dont to the heads which means the intake gaskets were replaced = check the bolts.

 

[93navajo]

will try tightening the bolts does anybody have the torque specs and which pattern I might need to tighten them in? Also recleaned the IAC and now when I start it , it seems to stall out at first, and with a couple of tries it starts up but the RPMS stay up at 1100 - 1200.

 

[410Fortune]

Dont forget to disco the battery when you clean the IAC or do anything.

It is normal for the idle to be 1200 or so for the first few drives AFTER the battery is hooked back up. The truck will re-learn and the idle shoudl drop back to 800 in a short time. If it does not then the problem is not fixed.

There is also a base idle re-set proceedure for the OHV 4.0L
Youcan find it here:

4.0performance.com

Try searching for the torque specs and proper sequence.

 

[93navajo]

I will try all that stuff I appreciate all the info this site has been very informative.

 

[93navajo]

Just another note after cleaning the I A C it now stalls on first start up and I have to resart it about 2-3 times. It is now running and idleing worse.

 

[Billy177]

did you reset the computer but you probrally need a new iac

 

[adidaswear]

do you have custom huskey mats? If so make sure they are over the gas pedal....done that to me a couple times....lol

 

[93navajo]

I did chceck the mats a couple of times LOL. I have now changed the IAC with factory. It tries to go down to about700 rpm but sounds like it is going to stall then as the vehicle warms up it climbs up to 1100 now. Also when I drive the rpm goes down slowly as my speed decreases, and after under 15mph it goes back down to 1100 rpm from about 1800rpm. Any ideas I am bout to bite the bullet and take it into the mechanic. I have reset the computer a bazillion times every time I change anything.

 

[88vert]

TPS comes to mind.You might want to check the resistance on it

 

[93navajo]

I replaced the TPS also, scratching head.

 

[93navajo]

Well Guess what I had the garage look at it finally. It was the intake manifold gasket and the O rings on the injectors were hard as rock so they replaced them. Truck is running like new, after new TPS and air intake valve, pcv, air filter and cleaning of the MAS, that I did. Just wondering also does anybody have a ball park figure on how much the intake manifold gasket and fuel injector O rings should have costed to replace with labor?