So for the past few months I've had a slight high idle issue in my 97 XJR. Yesterday morning I took apart most of the intake to be able to "feel/see" part of the throttle body linkage and feel the connector for the idle air control valve. I unplugged the connector and put everything back together and started the car up. Idle is where it should be at 800-900 in Park/Neutral and 650-750 in Drive/Reverse. Decided to plug the connector back in and idle is slightly higher again at about 200-300rpm higher than normal. So I left the connector unplugged and this morning starting the car up, it idles normal but after about 5 minutes the idles go straight back to slightly higher.

Not exactly sure what could be causing this, could it be a faulty MAF or throttle position sensor where the ECU adjusts the TPS to slightly open up to compensate for idle speed?

Any help would be appreciated to give me direction to help correct this issue.

Thanks!

 

try cleaning the throttle body AND the idle air port. They get gummy/dirty and the throttle tends to stick on the model. I also took the throttle body spring tower off and turned the return spring around 1 more turn tighter too. A common issue way back then.......gosh did I just say way back then? and Gosh too argh

 

I was attempting to do that the other day but trying to get to the throttle body without instructions is kind of tough. I stopped when I realized it looks like I'm gonna have to take off the whole intake assembly to even see the TB? Is there a better way to get to the TB assembly?

 

If you are going to clean your throttle body you can do it in situ. Just remove the air duct intake carefully, mindful that the low coolant level sensor wiring is zip-tied to the air duct. I jostled the air duct a little too hard with the low coolant level sensor wiring still in place and my sensor was damaged, which meant I had to look at a low coolant level warning light on my dash until I replaced the sensor.

Once the duct is removed cleaning the throttle body interior is easy. Use a carb/throttle body cleaner soaked rag and clean inside as far as you can reach but especially the ring around the inside where the butterfly valve closes. clean the sharp edge of the butterfly valve too.

Reconnect air duct and refit the low coolant level sensor if it fell out of the radiator reservoir void underneath, where it fits.

 

GatorJoe makes it sound easy and it is. But, this is an XJR. Cleaning is not easy. I can barely touch my TB with one finger, let alone clean it. Very bad English designing.

 

Yes OWRltd is correct, I need to clean the throttle body on an XJR. It is about 50 times more difficult than a regular XJ6 throttle body.

I have to spend about 10 minutes taking off the intake elbow that bolts onto the intake cover just to be able to barely get my finger onto the IAC connector to unplug it.
I wish there was a guide to follow to remove the throttle body on the XJR's. Like I said in another post, I did try to remove parts of the supercharger to be able to get to the TB assembly but going at it blindly is tough, I stopped where I realized I had to remove the whole intake assembly from the engine itself it looks like.

 

You can also use intake air cleaners taking out the air filter and spraying inside the tube to tb while running at 2k. I like bg products cause i know they work, seaform too. Read the instructions

 

I did this IACV cleaning on my X300 a couple years ago. Fixed the sputtering and stalling, but resulted in high 2000 rpm idle. Rough on brakes. After 20 or 30 trips it went away all by itself. The computer has a slow learning curve, I'm guessing.

 

YOU CAN SPEED IT UP WITH A HARD BATTERY REBOOT

 

So tried cleaning the throttle body today with the SeaFoam Intake Cleaner.

I sprayed it in between the elbow the comes out of the intercooler and the boot that leads to the supercharger snout. I figured the throttle body was on the other end of the supercharger snout.
Can't really tell if it cleaned the TB but made no difference in idle performance. With the IACV unplugged the car seems to idle correctly for about 1 minute but rises right back up about 200-300rpm.

My issue now is kind of confusing, using an ECU from a N/A XJ6 the car idles fine (Been kind of nervous to drive around other than idling in the driveway)
But putting the XJR ECU into the the XJ6 it idles fine also.
So now I can't figure out if it's my ECU not correctly adjusting the TPS/IACV or one or the other or both acting up. I don't have another XJR ecu to try out.

Brutal, when you use seafoam, where do you usually put it in for it to be fully effective?