Jeeps running weird

[Henchman]

So for the past two weeks I have been trying to diagnose this problem with my jeep. It started running weird. The idle started to vary and when I was driving at a steady speed and went to give it more throttle it had no response and lack of power. I could smell gas fumes. It seemed as it would catch up and I would have my power back. Then it threw a CEL. Po104. Which is the map sensor. So I changed that. Did nothing. Changed the o2 sensors seeing as they could throw that off to cause it and changes those did nothing as well. I started the jeep and sprayed carb clean looking for vacuum leaks etc. when I sprayed by the intake manifold it would cause it to run super shitty. So there's obviously a leak in the intake manifold gasket.

Do you think that the leak in the manifold would cause all of this? Idling funny, no power when on the throttle and has fumes?

Any advice and or suggestions would be greatly appreciated!

And don't say should have gotten a 4.0 mother fuckers

[hoggie101]

my tj did that when i have a crack in the manifold

[ct67_72]

Yes, that will do it. Definitely take care of that first

[CumminsJeep]

yea for sure. usually a vacuum leak like that will cause a higher idle or a random idle. when you step on the throttle it leans out which will give you that lack of power and run like shit. def start there

[doubleuj17]

The tj's had an issue were the wiring harness from the top of the intake runs around the back of the valve cover would rub through on the rear head bolt and it would cause all kinds of weird shit to happen.Dtc's for map,02,tps,iac and it would sometimes cause a hesitation when you gas it,the engine would torque enough to cause the head bolt to contact the harness.Check it out,i have seen it happen alot.

[Henchman]

So I replaced the o2s, tps, cps, the cat, plugs, wires etc. no bueno.

Did a compression test
1 - 165
2 - 165
3 - 140
4 - 165

Spec is 120-150.

Did a leak down test at 90psi

1 - 85-87
2 - 85-87
3 - 28
4 - 85-87

Verdict is an exhaust valve

[Henchman]

Hopefully I'll just have to pull the valve cover and replace a spring. If not then one of the valves might be shot, possibly because the cat was clogged, caused a lot of back pressure and heat and burnt it out. Then I'll have to pull the head

[Burton58]

Booo. Hopefully it's an easy fix

[Henchman]

Sooo. Update...


Jeep is still fucked.

How it started: When I would hit 3,000rpm the motor would choke/want to die out and or sputter, and the RPMs on the gauge would go CRAZY. From 3,000 to 6,000 then drop.
We started checking all of the easy "normal" things

Spark, fuel, air. Threw some codes for the TPS, and the CPS. New cat and o2 sensors. New plugs, wires, distributor. Did a compression test. It was fine. Then did a leak down test and the #3 cylinder had a leak. We pulled the head and had it fully redone. Came back and put it all back together. Long story short. It still does the same thing. Did a leak down test to check and make sure the head was fixed. The motor internally is good. Now its down to an electrical issue.
We checked the timing again and its fine.

Any suggestions to what we should look into next?


I just picked up an ECU from someone and I'm going to swap it with mine. If it fixes my problem then awesome. If it doesn't. Then I'm fucking stumped.

Someone HELP!

[Ruepart Hoaxley]

Is the harness fine on that back head bolt like Jeff mentioned?No rubbed-through spots?

[ct67_72]

Few things. Is the check engine light off? Do you have any codes?
The next step is probably to find a graphing meter and graph the injector voltage. Make sure its not loosing voltage anywhere.
If you have a code for a specific cylinder missfire you can swap injectors and see if it switches cylinders and follows the injector.
If you dont have codes have you pulled plugs to inspect and try and figure out which cylinder it is? If you did was one of the plugs wet, or cleaner than the others etc.?

[Henchman]

Few things. Is the check engine light off? Do you have any codes?
The next step is probably to find a graphing meter and graph the injector voltage. Make sure its not loosing voltage anywhere.
If you have a code for a specific cylinder missfire you can swap injectors and see if it switches cylinders and follows the injector.
If you dont have codes have you pulled plugs to inspect and try and figure out which cylinder it is? If you did was one of the plugs wet, or cleaner than the others etc.?

My buddy (who owns the shop) went through everything with meters and everything cleared. We pulled each injector and checked them accordingly. There are no codes as of now. All of the plugs have been changed and look fine. All of the grounds have been checked.

[Zullock Holmes]

ecu.

[Henchman]

Swapped the ecu, still does the same thing.
Getting frustrated!!!

[Ruepart Hoaxley]

Are you 100% sure it's electrical?


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