1. Home
  2. Jeep and Willys (new and old)
  3. Jeep Wrangler High Idle Problem

Jeep Wrangler High Idle Problem

Hello Everyone:

I have a 97 TJ and 95% of the time it idles perfectly. However, about

5% of the time, usually when the vehicle has been run for more than 20 minutes or so, the idle in neutral or park will shoot up to between 1200 and 1500 RPM. The only way to get it to stop is to put the vehicle into gear or to restart the car. If I restart it, it will not happen for a while, but it eventually comes back. The TPS was recently replaced, and I just replaced the idle air control valve, thinking this may have been the problem, but it still has the same effect. I'm thinking now that it may be the coolant temperature sensor (something wacky when the engine is hotter making the vehicle run at higher speeds??). Any suggestions? I'm hoping its not my computer...
Reply to
97tjMike
Loading thread data ...

Does the check engine light come on? Have you checked to see if there are any trouble codes?

Jeff DeWitt

Reply to
Jeff DeWitt

Engine light never came on, however I did check codes and this came up when I checked a few weeks ago:

42 An open or shorted condition detected in the auto shutdown relay circuit. An open condition detected in the ASD relay output circuit. An open or shorted condition detected in the fuel pump relay control circuit. An open circuit between PCM and fuel gauge sending unit. Circuit shorted to voltage between PCM and fuel gauge sending unit. No movement of fuel level sender detected.

However, I remember seeing that code a few months before this problem came up. I reset the codes a few weeks ago, and the other day I checked and that code hasn't come back.

Reply to
97tjMike

Clean the TPS connector. Go to an electronics parts store and buy some contact cleaner or WD40 works. Disconnect the TPS, clean, connect and disconnect several times, blow dry, then use some dielectric grease on the the connector seal ring to keep moisture out.

Reply to
Will Honea

Yup, replacing parts only cleans 'half' the connection.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06
formatting link
(More Off Road album links at bottom of the view page)
Reply to
Mike Romain

Reply to
97tjMike

The PCM uses the signals it receives from the TPS to adjust other systems on the engine. I would also recommend cleaning the IAC valve and connector. If it is sticking it can raise the idle speed up.

97tjMike wrote:
Reply to
c

The TPS is a resistance based switch just like a volume control. You can even test it with a multimeter set on ohms or live with the meter set on volts.

If it has a bad connection, this connection has a resistance factor that isn't supposed to be there or an arcing issue which causes surges.

When ours got a dirty connection, it would usually stall at the first stop and get stuck on a 1500 to 2000 rpm fast idle. We were told back in the 90's that we needed a new TPS in our Cherokee, We just retired the Cherokee recently with that same 'dead' TPS in it....

All the computer sensors are very low power items that are very touchy about their connections.

A spray can of electronic contact cleaner will be a very good friend to you as the Jeep gets older. It will sure save you money, because changing out parts only fixes 'half' the connection...

Mike

97tjMike wrote:
Reply to
Mike Romain

The best contact cleaner stuff is DeoxIT,

formatting link
You can get it at RadioShack, Fry's and other electronic stores:
formatting link
's everytime for me.Mike

Reply to
shaq

The Wrangler was in high idle today so I decided to investigate. I disconnected the TPS Sensor and the idle went back down to its normal RPMs. I then reconnected it and the RPMs went back up. Tried cleaning contacts, not help there. Perhaps the TPS is defective? It's still under warranty so I can just bring it back.

Mike

Reply to
97tjMike

You can do a voltage test on it.

If you have the AC off and the key just in 'run' with the engine off and back probe the TPS plug with multimeter probes set to volts, it should be at .02 volts at idle and 4.8 volts at wide open.

Mike

97tjMike wrote:
Reply to
Mike Romain

Reply to
97tjMike

One of them should be a ground, one of them's a 5v reference voltage that won't change and the other one should vary between the values Mike gave you as you move the throttle.

-- Old Crow "Yol Bolsun!" '82 FLTC-P "Miss Pearl" '95 YJ Rio Grande BS#133, SENS, TOMKAT, MAMBM

Reply to
Old Crow

ok tested. closed: .938v open: 3.9v

defective TPS?

Reply to
97tjMike

Sure sounds like it. The idle reading it high.

Mike

97tjMike wrote:
Reply to
Mike Romain

Throttle closed > 200 milliVolts Throttle wide open < 4.8 Volts Anything in that range will adjust. The way you

3.9 is low as well.

Measure the outer two pins to make sure your getting close to 5V.

Before getting a new one, run the old one back and forth a few dozen times with the engine off, then measure again. Also make sure the connector is clean and free of crudbunnies.

Reply to
DougW

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.