Getting sick of idle issue!

fourwheelford · Mar 5, 2010

Ok this has been going on for awhile now and I can't find the cause maybe some of you can help me. Basically after my truck warms up it idles anywhere from probably 900 to 1000, when I stop it settles to that point and doesn't rev up or down and it runs pretty smooth(a little bump now and then but nothing serious). Now when I park and put it into neutral or park it revs up to 1200 rpm and if I hit the gas while its in park it stops at 1500 and sits there, if I put it into gear it drops down to normal range. It happens off and on so it makes it harder to figure out. Im stumped on this, the truck has 6000 miles on a full tune up and probably 3500 miles on a fresh fuel filter and I just cleaned the maf and IAC three weeks ago. Fuel pressure is fine and no bubbles in the overflow, I was leaning torward the coolant temp sensor being faulty.

I have tried to spray for vac leaks but the damn fan blows the mist away, give me some ideas on where to spray because I think I may take the fan off to try and locate it but i don't want to run it for to long without it. It just seems like one stupid thing after another with this truck. If it was a vac leak the idle would be wierd all the time right? Thanks for any advice everyone.

babytruck · Mar 5, 2010

I assume its not showing any codes? might try a jy iac and maf that way you won't shell out a bunch of cash, chasing... other than the idle it runs fine? weird.

what did you use to clean the iac and maf? maybe causing this problem

fourwheelford · Mar 5, 2010

Yeah it runs fine otherwise, no codes, I used MAF sensor cleaner on the MAF and brake cleaner on the IAC I was carefull not spray near the motor side.

rngr4x4beast · Mar 5, 2010

ive got the same problem and i just deal with it. i look at it this way if it blows f**k it that means a supercharged 4.0 or maybe a 302 for betsy

JP02XLT · Mar 6, 2010

Have you checked the throttle cable? Mine was fraying on the 02 & doing very similar things.

JP02XLT

fourwheelford · Mar 6, 2010

I will check the throttle cable for sure, the fact that it doesn't do it all the time leads me away from a vac leak I will check for one anyway but im also thinking there may be an air bubble in the coolant and it may be the reason it doesn't happen all the time. I just don't understand why it only revs up in park, what is so different about park or neutral? Stupid crap like this pisses me off so much.

fourwheelford · Mar 6, 2010

Ok I was messing with it this morning and I have learned a few things, the first thing is that the throttle cable is ok and the second thing is that it idles up when the T-stat opens up. My driveway is sloped do I parked it with the front end up in the air and jacked it up also. I didn't have help so I had to rev the motor from the engine bay, I pulled the radiator cap off while it was running and the coolant was wanting to run out so I put it back on and opened up the overflow tank and watched that. While I was reving it every once in a while two or three little bubbles would pop up in the overflow so I know there was air in the system and the whole time it was warming up it was idleing at 1000 until the T-stat open and the idle jumped to 1200.

The overflow started to fill up so I cracked the radiator cap and got coolant so I tightend it back up and revved it some more, got a couple more little bubbles to pop up and the idle never dropped so I gave up. All of this was done with the heater on full blast, im stumped and ready to give up on this stupid thing. With all of this done does anyone have any ideas? I don't have a headgasket problem so lets steer away from that whole thing, no constant bubbles in the overflow, no coolant burning from the exhaust and no coolant in the oil. I guess it still could be air but I doubt it.

Viper Command · Mar 6, 2010

Are you shure it jumped when your t-stat opened? or was it when your o2 sensors came online. o2 sensors, tps, iac, egr, vac. leaks can mess with your idle very easly.

fourwheelford · Mar 6, 2010

I was holding the upper hose feeling for the pressure to release and right when it did the idle went up, really weird.

Viper Command · Mar 7, 2010

The only thing I can think of is static load on the water pump is released and the iac is not droping the idle. the same should be said for the power sterring.

to test that, remove the belt and start it (for a very short time) and see where the idle sits.

fourwheelford · Mar 8, 2010

I was trying to avoid that

I had one hell of a time getting that belt back on when I changed the tensioner I don't think I have cussed so much in a 30 minute time frame in my life

Plus it was 1000 degrees outside so I was sweating like a pig having to sit on the motor because of the lift, hitting my knuckles on everything. Not a fun time, maybe I got some crap in the IAC motor when I cleaned it before or it could just be on its way out it does have 106,000 miles on it. I will give it a shot though thanks

fourwheelford · Mar 15, 2010

HAve an update.

I realized that when my truck is stuck in a higher than normal idle I can unplug the IAC for just a second and the idle drops when I plug it back in the idle stays low. I think it is on its way out, do they just go out or can they go slowly? Also another question is can a malfunctioning IAC cause an automatic tranny to act funny?

Musick17 · Mar 16, 2010

rngr4x4beast said:
ive got the same problem and i just deal with it. i look at it this way if it blows f**k it that means a supercharged 4.0 or maybe a 302 for betsy

cheers to that. :icon_cheers:

dawson111299 · Mar 16, 2010

high idle issues are so hard to diagnose because there are so many factors here. Id start at the upper intake and trace all the vacuum lines out to make sure none are cracked. If those are all good try the iac unplug it and see if the idle drops if not its probly stuck or you have an intake leak or possibly a bad temp sensor. If the idle drops out almost to a stall when you unplug the iac it is working. to find an intake leak I spray some carb cleaner with one of those red tubes on it anywhere there is a mating surface. you have to use the red tube so you get a stream not a mist or the fan will blow it all over.

fourwheelford · Mar 17, 2010

The idle drops to normal when I inplug the IAC, I doubt its a vac leak because sometimes it will idle fine in park and other times it will idle up plus while its in gear it idles fine and only fluctuates up or down 100 rpm. I also thought about the coolant temp sensor but it would be constant like a vac leak. I think the stupid IAC is sticking sometimes and sometimes it will work right I can get one for under 90 bucks from the AP store but I would rather not spend the money if thats not it. I noticed it was doing this a couple months ago out of the blue so I figured it was the IAC so I cleaned it out and it helped a bit but still sticks. Stupid thing.

Getting sick of idle issue!

New Member

New Member

New Member

Member

Member

New Member

New Member

New Member

New Member

New Member

New Member

New Member

New Member

New Member

New Member

Sponsored Ad

Sponsored Ad

Today's birthdays

Member & Vendor Upgrades

Truck of The Month

Recently Featured

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store

Sponsored Ad

Sponsored Ad

Sponsored Ad

Amazon Deals