N3GH

All,

I appreciate any and all help with this jeep. Please excuse the long description but I figure it will help.
First problem as a slight miss and Coolant in the oil:
I change the Head Gasket twice and finally had the head pressure tested. Of course they found the usual crack between 3 and 4 cylinders.. Bought reman Head and installed.
Second problem is the rough running and misfiring codes. Mostly P 0305, cylinder #5. Sometimes there is P0306 and P0300.
Started when warmed up only but now it's all the time.
I have tested the compression both hot and cold,, About 140 to 150 and steady on all cylinders.
checked temperature sensor, Map Sensor, Throttle position sensor, Heaters on the O2 sensors, Grounds, and Idler air Servo.
After all this I noticed the most common code is the P0305 for Misfire #5.
Pulled the Fuel rail and checked Injectors,, saw a small crack in the plastic and thought that was it. Swapped the #5 and #3 injectors and re installed for verification. Hoped the problem would follow injector,, It didn't,, still Cylinder #5.
Pulled control wiring from injector #5 and found no misfire code but the code for injector circuit open. Which I expected to verify the electric connection was good. Cleaned the Cam Position sensor and magnet. Replaced the Spark plug/Coil Bar, and finally the Crank position sensor.

I think I am losing my mind with this. I am thinking about a computer but that seems unlikely. I did read the bulletin about the Carbon on exhaust valves but remember this is a remanned head.

Thanks

jpdocdave

swap a plug and see if it follows, i just had one like this, new spark plug was misfiring. and not because of gap either, sometimes plugs get dropped and gap gets screwed up, check for that also.

N3GH

Thanks,

I forgot to add I have replace the plugs first thing and have re gapped then switched them around like I did the injectors.
Thanks,, More ideas?

jpdocdave

man, you're doing a good job on the diagnosis, how about vacuum leak? maybe on manifold gasket or somewhere.

N3GH

Hmmm ,, Good thought!
I have not done a very good job on vacuum checking.
Some connections at the intake checked, but now you mention it the heater blower director reacts slower which I believe is vacuum activated.
Do you have a source for the vacuum lines for this jeep.
My manual doesn't show those.
Thanks

jpdocdave

i would check the manifold gasket first. i'm assuming its new with the head work, it needs to be replaced everytime though, i know you had to do it twice right? spray the manifold where it seals at the head with carb cleaner, or even water and see if it changes how its running. if the rpm's go up with the carb cleaner thats where the leak is, water will obviuosly make it sputter a little.

N3GH

Thanks for the responses.
I did put on a new manifold gasket but since the issue seems to be centered around #5 cylinder I will use your Carb Cleaner idea.
Perhaps I didn't tighten the manifold bolts in proper order and/or I left one out for final torque. I will check the torque first in a cold state. Then the Carb Cleaner idea and torque in a warmed up state.
Thanks for the idea. I will post my results.

jpdocdave

good luck, keep us informed

N3GH

Well back wit some news.
The torques on the intake bolts near the #5 port were just fine.
Next was checking all the vacuum lines going to the Heater Air Diverter.
Checking all the one way valves for leaks and found nothing.
Then to my amazement the hard line to the cruise control diaphragm was cracked and as I lifted it broke. Hmmm gotcha!@
I used a piece of hose to replace it and started it up.
No codes,, Ran it at idle till got to temperature and still no codes.
Still running rough.
Tonight I took it for a ride hoping the rough running was the computer learning once again. I was WRONG!
after reaching temperature and driving for a couple of miles I got misfire codes of P0305, P0306, and P0300.
At least it waits till it gets to full operating temperature to code out now.
Next test is to take for a ride tomorrow and see if the temperature and distance to code is the same.
Any Ideas??

THanks

jpdocdave

jeese, i was hoping that vacuum line fixed it. so have you figured out that #5 is the culprit? thats what it sounds like to me. if not, pull the injector connector while running and see if it makes a big difference, it should. compare it to a good cylinder when removing connector just to get an idea of the difference it should make while running. then from there i'd say first try another coil assembly. it is unlikely, but it really sucks when you get a bad new part and run around pulling your hair out trying to figure it out.

after that, if 5 is dead, you gotta look mechanical, thats all i can think. and you also said 5 and 6 sometimes, being next to eachother worries me. possible bad reman head, weak valve spring, or head gasket problem. there's a lot of reman companies now, they are not all good. they could've missed something. but after trying a second new coil i would also replace the manifold gasket. i've seen a lot of times that causing this problem when some one is sure it went on good.

good luck, i wanna see how this turns out.

N3GH

Well, I finally found the problem,
Your not going to believe it but the Exhaust lifter for #5 and #6 cylinder would not pump up. I replaced the lifters and all codes are gone and she running smooth once again!

Finally Done!!!!

Thanks all for the help.

xer0

what year jeep?

tjx54

2000 runs rough and misfire codes

thesplintercell

i get this code on my 01 because the #5 cylinder thinks the car over heats.. which is caused by the car contiuing to heat up after you shut it off and #5 being so close to the header it thinks its too hot..