Hello guys. I am totally stumped as to what is wrong with my jeep. I have been having an intermittent power loss once the jeeps is at full operating temperature. It almost seems like it running out of gas. So far i have changed the following:
Cap and rotor
NTK O2 sensors, both
I checked fuel pressure at the rail and it was solid at 49-50 psi.
I really do not know what else to do! Any suggestions? When cold runs strong then five miles later its lost 75% power.
No codes either.
Thanks for the reply. By power loss I mean if I put any kind of load on the engine it will buck and cut out. The jeep has never shut off it just will not accelerate. If i try and go WOT it may run up to 2500-3000 rpm and buck and cut out. I have not noticed any gauge issues. What connections are usually suspect?
Ok guys, so its looks like i may have finally found my bogging and hesitation issue when warm. After throwing more parts at it i decided to seafoam it. With the seafoam i discovered i have cracked exhaust manifold. Would i cracked manifold cause the issues i am having?
No problem and make sure you place your probes correctly on the pins in the connector to the crank sensor itself. Black probes goes on the middle B pin (ground cavity), red probe goes on the C pin (power, right pin w/locking tab up), and any resistance at all with meter set to the lowest ohm setting you have a bad sensor.
I have a 96 4.0 just like you and have found the crank sensor to be one of the most finicky electronic devices on a ZJ. And having clean grounds as mentioned in ZJ's dirty dozen thread, especially on the engine block, are super important.
I had a bad PCM ground on one of the coil studs which took out the PCM. The PCM grounds all the sensors so it most likely took out the crank sensor too. Didn't know any better back then and had the dealer replace the PCM but they didn't clean this ground wire off on the block. So it then took out another PCM and possibly another crank sensor. Not until all my grounds were clean, especially the coil stud which was corroded/covered in oil, did my problems cease. Of course it only took 3 PCM's, 4-5 bad crank sensors (shouldn't even count the 2 new/faulty aftermarket ones), and ZeeJay to figure this out!
If your crank sensor tests bad only go with a Mopar replacement and let us know how the test goes. Good luck!
Ok, that sucks. I am at a loss here. The thing runs fine cold and then gradually develops a bucking hesitation under load. It has never stalled and starts perfectly. Vacuum and fuel pressure good.
I had a bad TPS do that once. Weird.
Stay with the advice you've gotten so far, but keep a clogged cat in the back of your in mind...even though it's been replaced.
That cracked exhaust manifold can screw up your fuel trim after it's warmed up and it could even burn an exhaust valve if the crack is high enough on the manifold. I'd go ahead and replace it when I could, if it were mine. Get the one with the flex joints. While you're in there, you might as well swap the 5 large freeze plugs and the motor mounts too. Much easier doing it all at once.
Well I checked the crank sensor and the meter showed no change at all. Looks like its good. I guess next i will clean the grounds. One thing i noticed is that it now does not wait to get warm to run weak.
Ok I have another update. While driving in to work this morning, the jeep did the same thing. 15 mins into the drive the jeep would not take anything over 1/4 throttle. If I put in neutral and just hold to the floor is will rev to about 2500-3000 and just cut out and act like its out of gas. Now heres the weird thing, I get to work turn the jeep off and then restart it. Now with the restart it revs just fine?? I also noticed that when I cycled the fuel pump it only buzzed for a maybe second. Normally, when cycle the fuel pump is give a good 2 sec buzz.