very high idle problem...

[blazerguy912]

So I just put a motor in my jeep, everything ran fine, good idle and everything....Then all of a sudden the bottom radiator hose that runs to the water pump blew off due to the pressure and heat and fresh new antifreeze went everywhere...I forgot to tighten the clamp

Anyways, So I fixed that and everything and then it started to idle high...First I got an IAC sensor code, cleared that, didnt come up again but I still swapped another sensor in with a used one that i had from the other motor...still the same problem. So then i got some kind of idle malfunction code, cleared that, didnt come up again. THEN i got a tps sensor code, got a brand new done of those, but still high idle.. Only once or twice when I turned the car off and on did it go down to normal idle, so Im a little confused. Could it be some kind of idle sensor on the manifold?

Also, how do you check for vacuum leaks? What do you spray it with and what do you look for?


Also, i know this is not related, but I drove it today, and my temp went almost all the way up to redline, basically touching it. I opened my hood, and I just see smoke/vapors and some antifreeze coming from the thermostat housing!! All clamps were on and everything so Im a little confused where the antifreeze was leaking from. What could have happened? My overflow tank filled up with antifreeze quite a lot..Could it be that the thermostat didn't open when it should have, causing it to overheat? And should I be worried about my head being warped or anything like that?

[wannabejeep]

you can spray carb cleaner and listen for the engine to rev up to check for vacuum leaks.

This may sound dumb, but do you have the thermostat in the right way? Also those systems can be kind of a bitch to bleed the air out of. Make sure you run it with the heat on and the radiator cap open to ensure you get all the air out.

[blazerguy912]

LMAO yes i did put the thermostat in the right way..I knew I should have just gotten a new one when I swapped everything. and that will be the first thing I will do.

and i did have the cap off and heat on high, and poured in antifreeze until it didnt go in anymore, then it started to splurge out a little so I covered it with the cap..Is that good or should I have let it spill out until it would stop?

[wannabejeep]

Nah that should be fine in terms of bleeding it i think

[lilnapsak]

i had that issue over the summer.

pull the temp sender unit and clean it off real good with carb cleaner and or brake cleaner and reset the computer after. see if that makes a differance. if not replace it and see if that helps

dirty sender unit will screw with how much gas the computer wants to dump in it cauing a funky idle.


and the overheating issue could be a clog in the block..

[1cleantj]

as far as the high idle, my first guess would be a vacuum leak or dirty throttle body. (very easy to pull off and clean).

as far as the over heating... how's the oil look after the first drive ? what year motor did you put in ?

[blazerguy912]

I forgot to look at the oil, I was in a rush. As far as the engine, it was from a 96 and it went into a 2000

[1cleantj]

assuming you switched over intake/exhaust from the 2000 onto the 96 block. maybe a leak around the intake manifold ?

[customcreationsllc]

Did you verify the IAC is good?
Is IAC open (computer telling the engine to run high)
Or is the IAC closed the computer telling the engine to run low but it cannot compensate enough for something like vacuum leak.

I would start there unless something obvious like forgot to attach wire or hose or in your case loose clamp. even if you do it every day you still for get to attach a wire.

[blazerguy912]

How do you check the IAC? and nah all the wires are plugged in. I hope its just the iac but i dont know how to check it without just buying a new one lol

[clean4drxj]

i had that issue over the summer.

pull the temp sender unit and clean it off real good with carb cleaner and or brake cleaner and reset the computer after. see if that makes a differance. if not replace it and see if that helps

dirty sender unit will screw with how much gas the computer wants to dump in it cauing a funky idle.


and the overheating issue could be a clog in the block..

I've had this problem before and it did the samething but I also had a code.

[MikalCarbine]

How are you resetting the computer, a scanner? I'd recommend an overnight battery disconnect, especially after replacing the TPS

A vacuum gauge would be key to determining if its a vacuum leak or not. They are cheap at harbor freight or you can roll by and hook mine up if you'd like. I've been going through idle issues myself

I'd also recommend at least trying the following

Clean throttle body and IAC
Spray intake manifold with TB cleaner while at idle and listen for changes
Check vacuum hoses and elbows
Retorque intake manifold bolts (a pain in the ass)
Engine coolant temperature sensor
Check out O2/MAP sensors with scanner and maybe replace

Another crazy method is to do the following. Unbolt your throttle body and duct tape the manifold shut. From there unplug the brake booster line to the intake manifold. Now here comes the crazy part.. You'll need some duct tape, vacuum hose, a "T" connector, a cigarette and some KY jelly. The "T" connector will have one end connected to the baster, a cigarette duct taped to it and the intake manifold. You want to pinch the line going to the manifold while you decompress the baster and then pinch the line to the cigarette as you compress the baster. This will force smoke into the manifold and if there are any leaks, even small, it should be immediately noticeable. We all know what the KY is used for. Here's a picture of the setup

[Hydra]

Check intake manifold, I had unstoppable idle when I did a head job, turned out a piece of the centering studs for the intake had chipped off, allowing air to get sucked in.

[blazerguy912]

Yea, my dad helped me find it. It was a leak under the throttle body. Thanks y'all.

[DizzDizz]

To test for a caving leak u can just spray brake clean on the motor like around the intake manifold area. If u get a change in idle then that's where the leak is, cause the brake clean gets in.