01 XJ Will Not Idle

I have searched and found a few posts on the subject, but was wondering if anyone had any good ideas. I recently replaced the motor in my 01 XJ. The truck will only start if I give it gas, and will not hold an idle. But it will start and idle if I disconnect the vacuum hose going to the rear vent on the valve cover from the inake manifold. Once I give it gas, it revs fine. I replaced the battery, checked the grounds, cleaned the IAC and throttle body area and it still wont idle. Fuel pump is new. Where should I look next?

Next step is to test the throttle position sensor (TPS). It can be tested with an analog meter and a manual with the procedure.

BTW, I know you replaced the fuel pump but if the TPS checks out, you really should verify your exact fuel pressure with a gauge. For an 01, you should have 49.2 psi plus or minus 5 psi.

Good luck and let us know what you find.

You mentioned that it would idle if you disconnected a vaccum hose...maybe it is not getting enough air.

You cleaned the IAC, but does it work?