I know this issue has been discussed in the past however I have a few questions about vacuum lines.
I have a 98 TJ with the 2.5 four cylinder motor. I had a cracked exhaust manifold that I recently changed. While the manifold was off I cleaned up the intake manifold, replaced the throttle body with a newer used one (the one on it had a broken pipe between the MAP sensor and the throttle body itself- it was rusted so bad the little pipe broke). Prior to changing everything the jeep ran and idled great. After, it idles really high (like 2100 rpms) and if I touch the gas pedal, it revs even higher, hangs up there a few seconds, then back down to 2100 rpms.
I do not believe it is an intake manifold leak. I made sure that the intake was on flat against the head and the little dowels were clean and able to pop into the holes on the head for alignment. I used a brand new Felpro gasket and it went together very easily. I torqued in the correct order to the torque specs.
Today, I started it and placed my hand over the throttle body intake opening (without the airbox on) and it didn't change the idle at all. I also didn't hear any sucking sound or possible vacuum leak anywhere. It possibly lowered it 50-100 rpms but it was so slight I could barely notice. I'm wondering if I somehow put the vacuum lines on the wrong spots...I have looked up a few diagrams but I'm not sure if they match the components I have on my jeep. The intake manifold has 4 nipples under the throttle body. One goes to my brake booster, one goes to a small vacuum booster on the fuel rail, and two go to the vacuum canister that mounts on the fender. Does that sound right?
I am getting a P0108 code which is either vacuum leak or faulty MAP sensor. I changed the MAP sensor and that didn't make a difference.
Anyone have thoughts on how to diagnose what's going on? Can I remove vacuum hoses one at a time from the manifold and learn anything based on the response to the engine?
Thanks for any thoughts or ideas.
Mike
I have a 98 TJ with the 2.5 four cylinder motor. I had a cracked exhaust manifold that I recently changed. While the manifold was off I cleaned up the intake manifold, replaced the throttle body with a newer used one (the one on it had a broken pipe between the MAP sensor and the throttle body itself- it was rusted so bad the little pipe broke). Prior to changing everything the jeep ran and idled great. After, it idles really high (like 2100 rpms) and if I touch the gas pedal, it revs even higher, hangs up there a few seconds, then back down to 2100 rpms.
I do not believe it is an intake manifold leak. I made sure that the intake was on flat against the head and the little dowels were clean and able to pop into the holes on the head for alignment. I used a brand new Felpro gasket and it went together very easily. I torqued in the correct order to the torque specs.
Today, I started it and placed my hand over the throttle body intake opening (without the airbox on) and it didn't change the idle at all. I also didn't hear any sucking sound or possible vacuum leak anywhere. It possibly lowered it 50-100 rpms but it was so slight I could barely notice. I'm wondering if I somehow put the vacuum lines on the wrong spots...I have looked up a few diagrams but I'm not sure if they match the components I have on my jeep. The intake manifold has 4 nipples under the throttle body. One goes to my brake booster, one goes to a small vacuum booster on the fuel rail, and two go to the vacuum canister that mounts on the fender. Does that sound right?
I am getting a P0108 code which is either vacuum leak or faulty MAP sensor. I changed the MAP sensor and that didn't make a difference.
Anyone have thoughts on how to diagnose what's going on? Can I remove vacuum hoses one at a time from the manifold and learn anything based on the response to the engine?
Thanks for any thoughts or ideas.
Mike
