I have an 01 cherokee with a distributerless 4.0 it is throwing a cylinder 1 misfire. I have replaced the coil, the injecters, Plugs, and the TPS and it is still missing and has almost no power. it happens inconsistently usually when the jeep warms up. if i reset the computer it stops for a while then starts throwing the code again. anyone have any ideas? Im out.

Thanks a lot

Dunno about the problem, but it sounds like a sick XJ. Need to post some pics.

Check your fuel pressure. Could be your pressure regulator? Check it at idle, then pinch or remove the vac line. Fuel pressure should increase.

2nd test, monitor leak down of fuel pressure. Hook up fuel pressure gauge, turn vehicle on and run for a minute, turn vehicle off. Write down fuel pressure reading. Come back in 20 minutes, if it is dramatically lower you have an issue with an injector or the pressure regulator.

Are you throwing any other codes ECM/PCM? Check those first.

Thanks ill look at that, the only code i get is misfire on cylinder 1 it is saying it may be a problem with the electrical circuit for the first injector.

to test the injector circut, get a NOID light, it will flash as the circut cycles, if it misses a flash it's screwed

Also might be a bad Injector (coil or clogged)

Might be a bent valve or broken valve seat



I've been through this recently, I know your pain :(

check compression

do a compression check, if it checks out, swap injectors and see if the fault follows the injector. also make sure all your grounds are clean and tight

thanks, I changed the injector, followed the wires re taped the wires where they looked like the could be bad, i need to check the circut, and ill look at the valve seat.

Good luck man! I tracked one problem for two years! Run great for months, then run like shit... back to normal for months. Wound up being the ECM.

I would have to say it is the fuel pump, had a very similar problem with mine. I checked and replaced several things before doing the pump. Works great now. I have a 2000 Cherokee for reference.

Look at your plug wires at night in the dark....I had a random missfire on #2.It ended up being a bad plug wire that was intermittenly grounding itself out on the head.

Look at your plug wires at night in the dark....I had a random missfire on #2.It ended up being a bad plug wire that was intermittenly grounding itself out on the head.
there are no plug wires on distributorless ignition... has a coil rail bolted over the plugs...

There was a TSB for the distributorless 4.0's. The Cam position sensor (where the distributor used to go) can get out of phase. There is a tab that prevents you front turning it but something about the internals can slip...

the only way to see if that is it is to hook it up to a shop scope that can monitor the pulses from the Cam Position Sensor and the Crank Position Sensor. you need to be able to plot the data out on a time series and overlay the two graphs.

There should be a cam pulse and then 4 crank pulses (think about the 3 sets of 4 holes on a 4.0 flywheel), then a cam pulse and 4 crank pulses, then a cam pulse and so on...

On a faulty cam position sensor the cam pulse will happen during the 4 crank pulses. it cam be fixed without buying new parts apparently by grinding off the locating tabs and turning the sensor untill the pulses are right. but you could just swap in another sensor and see.

I actually have a cam position sensor complete with lower oil pump drive you can have for the cost of shipping if you wanna try it. It can out of a running 01 grand cherokee that i got the engine out of. (it had been totaled in a wreck).

PM me your addresse if you want to give it a shot.

also, try this:

http://www.wjjeeps.com/tsb_list.htm#1803103

I know this is alot and its for a WJ but dig through the whole thing....

http://www.wjjeeps.com/tsb_list.htm

Gumbo, thanks for the help, I replaced the crank position sensor Ill look into the cam position sensor. as of right now i think i will pass on your offer but i may get back to you about that.

i had a problem similar to this, it turned out to be a vacuume leak on one of the fuel injector o rings. the problem isnt solved, but it runs a lot better, i think i have a bad valve. good luck, i hate misfires.

Gumbo, thanks for the help, I replaced the crank position sensor Ill look into the cam position sensor. as of right now i think i will pass on your offer but i may get back to you about that.


You should take him up on the offer. You may want to decarbon the engine first though.