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bluedragon436
09-29-2015, 11:26 AM
I have a friend who is in my Jeep club... He used to have a nicely setup YJ, and has transitioned to a XJ, which is lifted and such.. Anyways.. since he got it, he has replaced the IAC and the TPS due to a high idle issue. He took it to a mechanic friend who did some troubleshooting and said he had a bad Intake/Exhaust manifold gasket, so he and I changed that out yesterday, and figured out whoever had replaced it previously, had not fully cleaned off the old seal, and that was certainly causing a leak issue, so cleaned it thoroughly and put new gasket on, and got it all back together.. Started it up, and she ran perfectly, started @ high idle, and dropped down to proper idle like it should.. let it run for a bit, then it started to climb idle a bit, then climbed to roughly 1600rpm.. where it stayed.. (which is the issue he had to start with..)

Does the same thing when you have it in gear, it'll drop down on RPM like usual, then say when you stop @ a light it'll go up on idle to roughly 1600-1800rpm.. To me it seems like it is still a TPS, but figure I'd ask folks that know far more then me, on these things..

Just wondering if anyone else has any ideas what might be causing this??

Brasscatz
09-29-2015, 02:35 PM
Hmmm... have you checked all vacuum lines?

bluedragon436
09-29-2015, 02:38 PM
That was kind of down to the point where we got to last night after getting everything back together... It's a 99, so has the newer intake, and either way not too many vacuum lines, thank goodness!! LOL

Brasscatz
09-29-2015, 02:40 PM
Then I'm thinking there might be a crack somewhere whether it be a crack in the TB or intake or something

4.3LXJ
09-29-2015, 08:40 PM
Pull the power brake booster line and plug the end of it and see what happens

bluedragon436
09-29-2015, 09:10 PM
Pull the power brake booster line and plug the end of it and see what happens

If it does drop the idle down, then I'm guessing it would be the brake booster that is leaking some where??

4.3LXJ
09-29-2015, 09:11 PM
Yes, probably the diaphragm

bluedragon436
09-30-2015, 12:05 AM
Yes, probably the diaphragm

Nice, have passed that along to him, and will have him try that tomorrow if he gets a chance... He is getting pretty discouraged with this issue... and I'm trying as much as I can to keep him going with it...

nickyg
09-30-2015, 12:57 AM
Pull the power brake booster line and plug the end of it and see what happens

Good advice, I never thought about the brake booster leaking vacuum.

bluedragon436
09-30-2015, 09:58 AM
Good advice, I never thought about the brake booster leaking vacuum.

Me either, or I would have thought to pull that line and check it the other day.. Actually I kind of looked at it, but was mainly to make sure it was all still connected and hadn't come loose, or looked cracked or anything, didn't think to pull it and try plugging it.