I recently had the fuel hose on the fuel pump in the tank go to mush and leak back into the tank and got that replaced as well as the other external fuel lines but now I have an "idle" problem. The engine starts and has 32 PSI fuel pressure but it runs at 2500 RPM and higher. Once it started after sitting awhile and ran at 1200 RPM initially but when I tapped the gas peddle it jumped up to 2500 RPM again. It did this once some time ago and eventually idled normally when I shut it off and re-started, but now it wants to race on each start. The accelerator linkage is free and returns fully to the stop screw when I turn it manually under the hood.

Before I take the intake tract off, is there anything I might check that could cause this high idle? Vacuum leak perhaps? Or is the butterfly able to move independently of the external linkage? Suggestions will be greatly appreciated as this has me scratching my head big time. Oh yes, it has 170K miles on it.

UPDATE: OK some of this is coming back to me now - too many vehicles to remember everything. I removed the rubber intake tract (the three torx screws were really tight) and the butterfly was was pretty clean, but the top of the throttle body had a layer of white powdery crud under the gasket. I scraped the white powder off with putty knife and chisel and cleaned the butterfly with CRC throttle body cleaner. I checked the butterfly clearance at .002” to .003” (002 slipped- 003 caught) and reassembled the intake tract using anti-seize on the three bolts. I disconnected and sprayed the Throttle Position Sensor connectors (two of them) with contact cleaner and also the connector for the other device beside it. When I started the engine cold it idled down to just below 1000 RPM and seemed normal again. I guess it was the TPS connectors having poor contact somewhere. I don't think I'll even have to adjust the TPS now that it is actually idling.

 

I picked up a replacement for my power steering pump and went out about 2:30 today to move the jeep up to the garage to replace the pump and when I reconnected the battery and started it, it again reved up to 2500 RPM and when I tapped the gas peddle it increased to 2700 RPM. I turned it off and restarted, but it still ran at 2500 RPM plus. Darn! Back where I started, so now I need suggestions. I know the intake is clean and the butterfly is set correctly and I wonder what could have changed overnight. I don't think a vacuum leak would fix itself and then start leaking again. Maybe Clean the TPS connectors again? I am scratching my head again. What the heck is it?

Another thought: I sprayed the TPS connectors with WD40 and then the idle was around 800 RPM cold, but in moving the Jeep and blipping the throttle the idle went to 1000 RPM and then 1200 RPM. So....New TPS? Or is it possible to clean the innerds of the TPS?

 

I've had no replies but just in case someone looks up this thread later, a new TPS from eBay ($9) fixed my high idle problem - at least for now. I set the TPS about mid way in its adjustment and had a cold idle of 1000 RPM and a warm idle of 500 RPM. What a relief that is. Now I just have to see if any Jeep dealer will honor the lifetime recall on the funky ABS system. The recall says:

DEALERS WILL TEST THE VEHICLE'S ABS AND REPAIR AS NECESSARY. THE WARRANTY ON ALL ABS COMPONENTS WILL BE EXTENDED TO 10 YEARS OR 100,000 MILES (EXCEPT FOR THE BRAKE ACTUATOR PISTON ASSEMBLY AND THE PUMP-MOTOR ASSEMBLY WHICH WILL HAVE A LIFETIME COVERAGE). OWNERS WILL BE REIMBURSED FOR PREVIOUS ABS COMPONENT REPAIR COSTS.

 

TPS and any kind of spray oil , seafoam etc dont play well together. Learned the hard way on that myself.

 

I've never sprayed the TPS itself but did spray contact cleaner on the connectors when it acted up. Apparently even though sealed they can wear out with age so I assume there is a potentiometer inside that can either wear through the windings or fail to make contact. My new one seems to work fine, but my new PS pump still foams and groans when the wheels are turned fully.