I recently bought a 2006 TJ with 145,000 miles on it. After driving it for 70 miles one of the rod bearings broke so I replaced both the 4.0 Liter engine and automatic transmission with new ones from Fraser Engines and Transmission. So far I have put about 400 miles on the vehicle after the install. Yesterday, while at idle waiting for a traffic light with my foot on the brake and the jeep in 'Drive' the rpm's jumped to 2,500 to 3,000 rpms with no input from accelerator pedal? My mechanic checked it out and there were no vacuum line leaks. He suspected the cruise control module was faulty and commanded the rpm increase so he disconnected the linkage to the throttle body and told me to keep an eye on it. After driving it home about 5 mile away the rpm's again went to around 3,000 rpm's while in 'Park' at my driveway and the windshield wipers started to go without turning them on? I have not messed with any of the wiring during this restore project. Could this be a bad engine control module or wiring harness? Anyone else heard of this happening or what it might be?
-
It's time to cast your vote for the third annual Ride of the Year (ROTY) contest! The winner will receive a free BMB big brake kit compliments of Blaine. Click here to vote! Voting ends December 31st at 12 AM MST.
2006 TJ has uncontrollable RPM at idle
- Thread starter falcondrvr
- Start date
I would disconnect the vacuum hose from the brake booster and plug the hose. Start the engine and see if the increased RPMs returns. If you have normal idle RPMs; then the problem is a bad brake vacuum booster.
Rubicon88
TJ Addict
Take off your negative battery cable and try to start the vehicle with key forward in crank starter position. Hood there for 15 seconds.
Hook back up, fire it up, see what happens.
Hook back up, fire it up, see what happens.
I just tried and it didn’t generate any codes that I could see. I held down the reset button while I did the 3 key flick and the display showed:
Sof 5.1 (Software version?)
713030
bUS 60
All of the indicator lights lite up separately and the gauges all moved to various positions. No codes were display that I could see.
I tried it before without pushing the reset button and it just showed ‘done’
I am new to Jeep’s and working on them so I am very thankful for everyone’s help!
Ok, I’ll do this tomorrow am, what does this do or is it a reset of something? Thanks!
The brake booster wasn’t the issue. He said there was a small rise in rpm, only about 200-300rpms when he did this. Thanks!
After speaking to our new engine manufacturer, my mechanic has swapped out the old idle air intake controller for a new one. Testing showed that when the old AIC was manually turned on with the engine running it increased the rpm’s by ~1,500 rpms. Hopefully this ends up being the problem, otherwise he’s looking at the engine computer module.
Before going to the extent of replacing the ECU; disconnect the (4) 32 pin harness connectors from the ECU, check the pins for oxidation and then firmly snap the connectors on to the ECU receptacles.
Inspect the harness wire loom that goes around the back of the valve cover on the right side to ensure that it is not rubbing on the head bolt (know problem), but I am doubtful this would cause the problems you are describing.
Inspect the harness wire loom that goes around the back of the valve cover on the right side to ensure that it is not rubbing on the head bolt (know problem), but I am doubtful this would cause the problems you are describing.
I had something similar to this, turned out to be the TPS (I had a code) make sure that the one in the Jeep is OE MOPAR (this sensor in particular is really finicky) and I would try replacing g that before the PCM or anything major. There “only” 60-70$
We switched out the Idle Air Controller with a new MOPAR one and I drove it 40 miles yesterday with a bunch of stops to idle, no issues so far. I think I'll switch out the TPS too with a new MOPAR one. Trying to cover all my bases before messing with the PCM.
I did notice yesterday that when driving at 55 mph the rpm gauge was steady at around 1,700 rpm but the engine had a slight surging noise but not noticeable on the rpm gauge. When I turned off the Overdrive it went away after being at the higher 2,200 rpm. I recently changed the differential gears ratio's from 3.73 to 4.10. (I'm running 33' tires). Any thoughts on that? It seems like the rpm is too low so the new engine and transmission are struggling. Only the high gear creates this noise.
Thanks for you insight!
Maybe if the gears were loading and unloading quickly, what condition are your suspension bushings in? Maybe the axle is twisting slightly causing the engine to load and unload on the tires? Slight misalignment on the gears?
A/T or M/T? If it’s A/T maybe something with the fluid level and or a filter block?
M/T I would say a dying mount or bushing somewhere, clutch slip would be more drastic.
My bet is still on the TPS, when that thing went bad the Jeep was all hell to drive, did something different at every light. Real fun to clutch when the engine has a mind of it’s own.
My mechanic just installed Quadratec's 3.5" Fox Shocks lift with all new steering components so the bushings and everything else is brand new. It has a new automatic transmission and new 4.0L engine with 450 miles on them so far. Still using break-in oil on the engine and front/rear differentials which are now at 4.10 ratio. Definitely gonna put in a new MOPAR TPS.
Int
Interesting, so we are dealing with all new parts. That could be useful later. For now I say do the TPS and report back. Remember to re-set the computer after replacement.
My mechanic just installed Quadratec's 3.5" Fox Shocks lift with all new steering components so the bushings and everything else is brand new. It has a new automatic transmission and new 4.0L engine with 450 miles on them so far. Still using break-in oil on the engine and front/rear differentials which are now at 4.10 ratio. Definitely gonna put in a new MOPAR TPS.
Ok I'll let you know what happens. I'm sure my mechanic knows but how do you reset the computer for the new TPS?
Disconnect the battery's negative connector for 2-3 minutes to reset the computer.
Regarding the TPS being the possible cause of the high rpms, I would bet the mortgage they are not being caused by the TPS. The TPS cannot let the additional air into the engine that would cause/allow rpms like that. I'd bet $$$ there's a big vacuum leak somewhere and it wouldn't surprise me to learn it was caused by an imperfect seal between the intake manifold (the engine's source of air) and the head.
Regarding the TPS being the possible cause of the high rpms, I would bet the mortgage they are not being caused by the TPS. The TPS cannot let the additional air into the engine that would cause/allow rpms like that. I'd bet $$$ there's a big vacuum leak somewhere and it wouldn't surprise me to learn it was caused by an imperfect seal between the intake manifold (the engine's source of air) and the head.
I was going to bet vacuum leak, but the OP said he “had it checked” I know my 01 was idling and surging iradically, and when I replaced the TPS the problem fixed itself. But now that you mention it, it is odd that it could surge that much without control of the air flow. Maybe I bumped into and fixed a leak while I was there?
After my mechanic installed the new idle air controller I drove my Jeep for about 40 miles with numerous stops where it was at idle. The engine ran good with no idle rpm increases or surges. Did the new IAC solve the prob? Not sure but it ran good. If there was a big gasket leak or vacuum leak I would think it would have shown up on my last drive? I’m new to Jeep’s and this is definitely a head scratcher. Thoughts?
Similar threads
