Need Help: High idling after tune up

Hey guys, I need a little help. This weekend I gave my XJ a tune up. I am quite pleased with the results. First off, I installed an aftermarket cone filter using some home made mods which seem to work just fine. All vacuum hoses except one (the smallest hose coming from the air box) are jooked up. I followed the instructions given by XJ-Armor.com. I made my own intake adapter out of some thick rubber tubing made for plumbing. Anyway to keep this short, I followed instructions, everything is where it is supposed to be and nothing leaks. I pulled the throttle body off and cleaned the s**t out of it. Cleaned the ISA. New cap, rotor, wires, and plugs. Adjusted the TPS to the lowest idle I could get it to. When the engine starts up, it purrs like a kitten. Couldnt ask for a better idle. But when I get going and get warm, it tends to idle a little too high. Dont have a tach so I dont know how high, but I know its too high. This causes the XJ to run a little warmer than usual. I just did it this weekend so I dont know how gas milege is going to be affected. Did I mess up my ISA by removing and cleaning it, or is the intake allowing too much air into the engine and causing it to idle higher. It now runs like a bat out of hell, I love it. I also unplugged the battery over night to reset the comp. Any and all help is greatly appreciated. Thanks guys.

90red

Kind of hard to tell without a tach to go by. But I would say the TPS is your starting point. Also your bringing in more air now with the cone filter that might have something to do with it. But I would adjust the TPS so it idles at a smooth 6-700 rpm. Mine idles around 400 at start up and goes up to 7-800 after it's warm. I just need to clock the tps to have it idle at the right spot everytime. I'm sure someone will chim in on this later. Juice

juicexj24 said:

Kind of hard to tell without a tach to go by. But I would say the TPS is your starting point. Also your bringing in more air now with the cone filter that might have something to do with it. But I would adjust the TPS so it idles at a smooth 6-700 rpm. Mine idles around 400 at start up and goes up to 7-800 after it's warm. I just need to clock the tps to have it idle at the right spot everytime. I'm sure someone will chim in on this later. Juice

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I agree that the TPS is a good starting point, but it really should be adjusted by voltage, not idle speed. The computer should adjust the idle speed correctly if everything else is right.

But since you also did other work, I'd also suggest checking for a vacuum leak (i.e. what did you do with the spare line?), a leak in the throttle body gasket, and damage or poor seating of the idle air controller pintle. And make sure the rubber connector for the MAP sensor got on right way around.

All great advice. Thanks alot guys.

90red

on one of my 4.0L throttle bodies (my original one) the bore around the butterfly actually wore a groove and did not close off enough to allow the IAC to even do its job.

I suggest you check the bore, and if there is a groove or notch, you can let the butterfly out a little by the set screw, or just bend the stop out for the butterfly.