Hello, so last time I posted on here my XJ had a misfire and an evap code. Well, I replaced the coil pack, put all new 4 hole injectors in, new cone style air intake, magnaflow exhaust, changed the oil and coolant, new water pump, and I swear it has only made things worse lol. Now, some days the Jeep will idle perfectly around 750 and other days, it will flutter between 250 and 500 and sometimes dies completely. Yesterday after starting it up it was sitting around 250 fluttering and when I pumped the brakes it brought the idle up. It was almost as if I could control the idle through the brakes. As of now I have a no bus code, a large evap leak (already replaced the gas cap with a factory replacement), and the cylinder 5 misfire that came back a few weeks after the coil pack was installed (already replaced the spark plugs and gapped them to 35). I am at a loss. When I look under the hood, it sounds like there is a leak somewhere because there are fumes coming up from the intake side, but I can't pin down where its coming from. Any help would be appreciated. Thank you. 2001 Jeep Cherokee Limited 4x4 4.0L

 

Idle problem sounds like a vacuum leak. The fumes coming up from the intake side maybe a crack exhaust manifold.

 

For the exhaust leak, check everything youve done.

For the No Bus, disconnect the crank sensor and see if the No Bus is gone. A shorted crank sensor will throw that code. Disconnecting it removes the short. A poor connection with the cluster can throw the same code, but its quicker to disconnect the crank sensor to check the sensor, than pull the cluster.

If you can control the idle with the brakes, id say thats a vacuum leak. Those can hard to find sometimes. Dont just check the lines, but the rubber bits. Squeeze them. If you can see cracks, replace. What ive done on other vehicles was to pull the vacuum hose for the booster off the vacuum source (at the engine if i could get to it) and plug the port. If the idle still changed when i depress the brake pedal, id grab a wiring diagram and start tracing wires to see what, if anything, was wired into the brake switch circuit. Not tried this with an XJ, but i dont see it wouldnt work. Its a start, anway.