Average Cherokee enjoyer

Hello fellow Cherokee owners I have a 94 Cherokee Sport with a 5 speed manual that has a bad misfire at idle. It seems to be only on one cylinder and only does it when it’s warm. It goes away as soon as you bring it up off idle but does it again as soon as it goes back down. Starts just fine runs fine and doesn’t try to die just misses really hard at idle. I have held off on the parts canon for now all I did was put new plugs and distributed cap and rotor and down stream o2 sensor. Thank you.

tech

Sound like it could be a vacuum leak have you checked for that ?

Average Cherokee enjoyer

I found one that when from my intake manifold to the back of my fuel pressure regulator but I put a new hose on it and it helped a little but it will still miss at idle w when it’s warm. I haven’t found any other leaks but if you know an easy way to find them that would be great

tjwalker

Finish the tuneup, regardless of whether it resolves it, needs to be done. New high quality plug wires and a fuel filter. Both inexpensive and easy to replace.

Test fuel pressure. Must be done with a gauge which can be rented inexpensively at most parts stores if you don't have access to one. At idle, you should have approximately 31 psi. Then disconnect the vacuum line leading to the fuel pressure regulator under the hood and pressure should jump to approximately 39 psi. If there is any raw fuel in that vacuum line, replace the fuel pressure regulator as it has a ruptured diaphragm.

Simple stuff first. This is a process of elimination.

tech

You can use carb spray but it can catch fire or you can use propane with a hose so you can put it where you want . I would check the intake manifold gasket . and maybe check to if any of the bolts are loose .

MKP

The brake booster can hide a vacuum leak. Easy enough to test, just plug that line and see if it improves anything.

bluejeep2001

From past experience , your miss does not go away at off idle, you can't feel it due to its short duration

agreen

Engine mounts?