Okay, here is a new one for me. This afternoon I ran over to Home Depot for some supplies. After we left, the wife wanted some dinner, so we stopped in a drive thru. While we were sitting there, my jeep (2006 Rubicon, 4.0 I6, manual trans) jumped up to high idle and wouldn’t come back down. By high idle, I mean between 1500 and 2000 rpm. We drove home and I took a look, but can’t find anything obviously wrong. Has anyone had this happen to them before and what did you find? Any answers would be greatly appreciated!
Jeep went to high idle and won't come back down
- Thread starter Radioflyer1105
- Start date
Might just be a stuck throttle cable. Check under the hood to make sure nothing is jamming stuff up. Anything more serious than that would have thrown a code. Is your gas pedal completely clear of crap?
Nope, no codes. I will check the cable. Thanks! I will have to check the vacuum system as well. Sure wish there was a diagram of that system out there. I have looked before and couldn’t find one
Isn't there one in the FSM?
Jeep Wrangler TJ Factory Service Manuals (FSM) & Technical Documentation
Check the CCV hose. Since this happened "suddenly", I'll assume the rear CCV elbow in the valve cover is the correct version.
ToddL
TJ Enthusiast
I had a bad TPS on my XJ that caused a high rev issue. But it was stuck at like 4000 rpm. Pretty scary situation.
The CCV is not a vacuum hose, it just vents crankcase gases back into the air intake. It would not cause an idle issue.
My bet is you have a vacuum leak somewhere RadioFlyer, check out the above vacuum diagram for some ideas. I doubt the throttle cable has anything to do with it.
I beg to differ, and the heck its not!
The CCV *IS* a vacuum hose, it connects directly to the intake manifold - pop it off and then tell me that's not a (massive) vacuum leak. I just went through this exact problem with my TJ - in my case because somebody put the wrong (open-type) elbow on the valve cover end so the engine was drawing air from the airbox via the front elbow, through the crankcase, and into the intake. This is a vacuum leak in my book - and resulted in a high idle, similar to my understanding of what the OP is experiencing. If the CCV hose has a leak, that's a vacuum problem.
I'm not saying this is the what or where of the OP's problem, but its something that should be checked. Simply remove the CCV hose from its attachment point on the intake manifold and completely block the barb fitting. That's how I found my particular problem.
Uh, yes it is. Take it off and put your thumb on it and tell me it isn't sucking in. How can it not be under vacuum? Its connected directly to the intake manifold!
It sounds to me like we perhaps have a communications SNAFU, and aren't understanding each other. All I can tell you is that hose SUCKS big time - it draws from the crankcase through a tiny orifice in the rear elbow (0.060" I read somewhere). If it leaks, its a vacuum leak. If you don't believe me, ask your MAP sensor!
It sounds to me like we perhaps have a communications SNAFU, and aren't understanding each other. All I can tell you is that hose SUCKS big time - it draws from the crankcase through a tiny orifice in the rear elbow (0.060" I read somewhere). If it leaks, its a vacuum leak. If you don't believe me, ask your MAP sensor!
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The CCV hose is exposed to engine vacuum which draws out engine vapor/gases into the intake manifold for combustion, but is not the what is considered a part of the vacuum system that operates the brake booster, cruise control, climate controls, etc..... So since it is exposed to engine vacuum; it can experience a vacuum leak as Zorba stated....
Gentlemen, thank you for all the valuable advice and discussion. As I started to troubleshoot the vacuum system, I finally threw a code. Drove it to the auto zone and it came up with the IAC sensor malfunctioning. There is a thread here about cleaning it, so I checked it out. It’s to the center of the engine on the throttle body. One torch screw holding it in. Took it off and found it was very dirty. Shot it with B12 and cleaned it up nice. Verified the plunger moved smoothly and reinstalled. Upon engine start up, idle came down and held rock solid at about 700rpm. Have the throttle body a good cleaning while I was there. Problem solved! Once again, thank you very much for all the suggestions and advice!
That's where I went with the same problem, but in my case the cleanup didn't help. Finding the wrong CCV elbow with the massive vacuum leak did - BUT - I got a clean TB out of the deal, and even bought myself a code reader so its all good!
John Wolf
TJ Enthusiast
I've got a similar problem, high idle after engine warms up. Sprayed TB and IAC several times with cleaner but problem doesn't go away. Got to learn how to check my vac lines since that was mentioned. I did notice something peculiar if someone can shed some light. There is an exposed nipple on the side of the intake manifold I never noticed and it does vac when I put my finger over it. See the pic and please advise as to if this is normal. Finger is pointing to the nipple.
Thank you all!
Thank you all!
Yes that will cause an idle problem and should not be open, so look around for a loose line but either way cap it off. Vinyl tape is fine for a temp.