High idle in park only? (Introducing my self)

First off I want to introduce my self I haven’t been part of a forum in a very long time! Very excited to join see a lot of active users and tons of useful information. Im from south jersey & this is my second Cherokee XJ & ever since I kinda have a thing for them & grew on me tons! Anyways I’m not the type of guy to start new threads asking the same thing but I haven’t gotten much information reading on similar issues. (I know it’s annoying) how ever I also kinda wanted to introduce my self! First off the Jeep I’m currently working on is a 1998 XJ bought it after selling my first one that I 110% regret! So this one was to kinda replace the one I had before. I’m having an issue with the idle, it idles high only in Park (1000-1100RPMs) I can throw it in neutral and the idle will go back down and idle normal. I’ve replaced a list of things like the following brand new :
1. Throttle Body
2. IAC
3. TPS
4. MAP
5. Coolant Temp Sensor
6. ECU
7. Neutral Saftey switch
8. O2 Sensors
9. Bosch 4 Port Injectors

That’s all I can think of right now. I bought 2 new extra TPS (cheap ones) just to diagnose if it’s the problem I will definitely replace with the mopar. I’ve read story’s of people getting faulty TPS brand new so I just ordered 2 more with a brand new pigtail. I also read that the ground on the TPS can be an issue. So I’m thinking about running the ground somewhere else just to check if that’s my issue. I checked the manifold bolts with brake cleaner while on no leaks there. I also did a vacuum test with a good ol cigarette & no smoke from anything else. So no vacuum leaks I think. Forgot to mention there is no check engine lights at all. One day messing around with a cheap scanner trying to go in deeper than I should I got a P1698 code but I disconnected the OBD2 scanner plugged it back in and deleted it and it never came back. Im kinda going crazy here so I’m turning to people with way more knowledge than me to try and figure this out. I’m somewhat mechanically inclined and not afraid to tackle most things. Atleast things I can handle lol. Anyways thanks guys I’d appreciate any feedback. Here’s a pic of my Jeep for you guys


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Welcome!

What do you see for idle in gear (R/D/1-2)? Is it similar to neutral or park?

This is only a guess, but I'm wondering if maybe the shifter linkage might be out of adjustment slightly and it might be causing the idle to increase to compensate for the load of being in gear.

Rob Mayercik said:

Welcome!

What do you see for idle in gear (R/D/1-2)? Is it similar to neutral or park?

This is only a guess, but I'm wondering if maybe the shifter linkage might be out of adjustment slightly and it might be causing the idle to increase to compensate for the load of being in gear.

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Hi rob! The idle drops ass soon as you drop it down from park into any gear! The problem is only when in park. I asked the PO if he knew anything about it just to get pointed in the right direction. Guy tells me something about adjusting the idle screw on the TB but this is a 98 there’s no screw that I know off & I put a brand new mopar TB on it.


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I would focus on the IAC for now. Since the sensors work off of 5 volts resistance is super critical. Checking the resistance "point to point" and applying some Nolox would be a great idea. Check the voltages when it's idling.

RCP Phx said:

I would focus on the IAC for now. Since the sensors work off of 5 volts resistance is super critical. Checking the resistance "point to point" and applying some Nolox would be a great idea. Check the voltages when it's idling.

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It’s on its 2nd iac what would you recommend for me to do exactly?


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sharkowl said:

It’s on its 2nd iac what would you recommend for me to do exactly?

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This

RCP Phx said:

Since the sensors work off of 5 volts resistance is super critical. Checking the resistance "point to point" and applying some Nolox would be a great idea. Check the voltages when it's idling.

Click to expand...

RCP Phx said:

This

Click to expand...

How to you check them? Sorry I’m pretty bad with electric stuff



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Had me stumped, I had no logical reason why it would this and then boom. Maybe someone wired in a high idle switch? The switch may be hidden from view like under the knee panel. A high idle switch is a standard feature on Police models, still in the programing for civilian models just not present.

Or another *remote* possibility is the high idle wire is clamped behind something and grounded, high idle may be a ground activated ECM function.

8Mud said:

Had me stumped, I had no logical reason why it would this and then boom. Maybe someone wired in a high idle switch? The switch may be hidden from view like under the knee panel. A high idle switch is a standard feature on Police models, still in the programing for civilian models just not present.

Or another *remote* possibility is the high idle wire is clamped behind something and grounded, high idle may be a ground activated ECM function.

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Funny you said that. Because I actually think this may be a police model. But than I thought about the oem color which is red. Than I thought police model was maybe bought for a fire station? If it’s a police model is there anyway to adjust that what would the idle switch look like? Idle doesn’t bother anything but I’m so picky it bothers me more than anything lol


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8Mud said:

Had me stumped, I had no logical reason why it would this and then boom. Maybe someone wired in a high idle switch? The switch may be hidden from view like under the knee panel. A high idle switch is a standard feature on Police models, still in the programing for civilian models just not present.

Or another *remote* possibility is the high idle wire is clamped behind something and grounded, high idle may be a ground activated ECM function.

Click to expand...

Almost positive now that this was a police vehicle before, it has those holes that look like things that were mounted on there



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If it was a police special it would have the switch in the bezel next to the rear wiper/defrost switches. The system runs thru the PCM and performs a total different function so it couldn't be related to what your experiencing.

It sounds like the high idle circuit is permanently wired to be on.
I added a high idle switch to my 2001 XJ, it idles at the normal RPM in gear and higher in neutral, between 1000-1100 RPM.

lazyxj said:

It sounds like the high idle circuit is permanently wired to be on.
I added a high idle switch to my 2001 XJ, it idles at the normal RPM in gear and higher in neutral, between 1000-1100 RPM.

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Yea that’s exactly where mine idles. I did a lot of research today on service package models & I personally don’t think it was. At first I did think so. I’m sure someone wired the high idle switch I guess now to fish for it and see where it could be wired to do a proper switch. As of now it’s not bothering me as much just because I’m 99% it’s nothing else but that. I just hate to play these finding games lol. If anybody has ideas of where people usually jump these wires too Id love to know.


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sharkowl said:

Yea that’s exactly where mine idles. I did a lot of research today on service package models & I personally don’t think it was. At first I did think so. I’m sure someone wired the high idle switch I guess now to fish for it and see where it could be wired to do a proper switch. As of now it’s not bothering me as much just because I’m 99% it’s nothing else but that. I just hate to play these finding games lol.

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This is a situation where a genuine Factory Service Manual for your year XJ is priceless. Every home XJ mechanic needs one.
The wiring diagrams will show where the high-idle circuit is accessed, it's a single wire that goes to ground when turned on.

Here's a vid of someone wiring up a high idle switch. Perhaps you can "reverse engineer" it to check and see if the pin is grounded.

https://www.youtube.com/watch?v=1kQqcXe-GNM

Saudade said:

Here's a vid of someone wiring up a high idle switch. Perhaps you can "reverse engineer" it to check and see if the pin is grounded.

https://www.youtube.com/watch?v=1kQqcXe-GNM

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Watched the video & it’s a very good video I’ll definitely get back to you guys after I look into it. It’s been raining down here & work has been hitting me hard (tractor trailers) so maybe this weekend for sure.


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If I get this posted it's from a '06 thread......
[/QUOTE]

RCP Phx said:

If I get this posted it's from a '06 thread......

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[/QUOTE]


Thanks man that’s very helpful


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