4.0L Multiple Cylinder misfire
- Thread starter Utah_jeepster
- Start date
Utah_jeepster
Super Moderator
Another swing and a miss....oh shut up chip lol. I am now having nightmares that it might be my heads and not having the money to fix them. I have enough bad dreams of what the heck the problem might be without that one creeping in adding a whole new dimension of sleeplessness.
P.S. what did the total cost of replacing the heads cost?
P.S. what did the total cost of replacing the heads cost?
Chip01TJ
New member
I don't have the cost handy as the dealer I bought the Jeep from was responsible to make it run right and I made them. The final numbers they put in were in the neighborhood of $4000.00. Nice to see a dealer get it once in a while huh? I have read a lot of reports of Jeep's 4.0l having lazy valve springs though. The last valve job I had done on an old GMC I owned was about $150.00 per head and pulled them myself. Good luck in solving your issue. If you diagnose valves you might be able to find a cheap head off a wreck or something but still a risk over a fresh valve job. Unfortunately a misfire can be very vague for cause. They replaced the coil pack, ECM, traced out all the wire harness looking for shorts, TPS, checked the injectors. They even had another Jeep on the lot and spent much time swapping sensors and test driving. The Jeep dealer finally diagnosed the bad head.
Sent from my iPod touch using Jeepz
Sent from my iPod touch using Jeepz
Utah_jeepster
Super Moderator
Well I just replaced the fuel pump and pump assembly, so far I haven't been able to get it to throw a code. Knock on wood I think I have fixed it.
Sent from my Android using Jeepz
Sent from my Android using Jeepz
I have a code 43 and according to many forums, it could be many things.
Valve springs, and or head, fuel issues..injector(s) etc
Jeep TJ Diagnostic Codes
I don't know where to start
Valve springs, and or head, fuel issues..injector(s) etc
Jeep TJ Diagnostic Codes
I don't know where to start
I have a code 43 and according to many forums, it could be many things.
Valve springs, and or head, fuel issues..injector(s) etc
Jeep TJ Diagnostic Codes
I don't know where to start
Valve springs, and or head, fuel issues..injector(s) etc
Jeep TJ Diagnostic Codes
I don't know where to start
Utah_jeepster
Super Moderator
Give me some back ground info, year of jeep, motor size ext, ext and let's see if,we can help you.
Sent from McDonald's happy meal toy phone using Jeepz
Sent from McDonald's happy meal toy phone using Jeepz
jpatterson
New member
hey there utah, looking at your pictures i see you are using e3 plugs, DO NOT DO THAT!!! use the stock plugs unless you have upgraded the rest of the ignition system to work (well) with high end plugs
Chip01TJ
New member
Just some advice with a misfire... If it is misfiring real bad and causing your rig to run terrible don't let it go like that too long. My Jeep went a couple months running like that off and on and eventually I fixed the misfire but the cat failed a few months after all that fuel getting pumped down the pipe. I attribute that expensive repair to the misfire problem. I swapped all the O2 sensors first too trying my best not purchase a new cat.
Utah_jeepster
Super Moderator
After everything I have done still never got to tge bottom of this. When the money comes available going to pull the head and have it rebuilt. Thinking it might be the exhaust valve springs as one article I read suggested.
Funny, I read a similar article/post over at either Wranglerforum or Jeepforum. Hate to have to spend that much cash but... The worst thing is that it doesn't effect my nice, smooth ride, only passing smog and that just takes a reset to get rid of the code. My milage has gone down to about 11/12 and wonder if the head has a lot to do with it.?
Either way, good-luck, thanks for the reply and post if and when you decide to take this route.
Tony
Michael Murphy
New member
Multiple misfire in a 2001 WJ Grand Cherokee with 4.0. Shop replaced Crank Sensor with a warranty Auto Zone that I had installed the year before and still same multiple misfire and cylinder misfire. Then replaced with genuine jeep crank sensor from Chrysler and fault cleared. Drove for a week now including 700 mile trip to Southern California and no misfire or check engine light and we pulled plenty of grades that had it winding hard. Be very wary of aftermarket Chinese junk parts. They have stranded me more than once.
JPNinPA
Active member
It is not difficult. The hardest part is it is near the top of the bellhousing passenger side. There is a bolt and an electrical connection.
As stated be sure you use OEM sensors. This one in particular. The sensor deeds to have the paper spacer over the sensor when installed. This sets the safe space from the ring and insures it is not damaged when the vehicle starts. If it doesn't have the spacer the ring damages the sensor and the issues you had will continue.
The symptoms of a failing crank sensor CPK is engine randomly not starting or shutting off while driving. When it fails the engine just doesn't start.
A failing or bad cam position sensor CPS depending on the year jeep is either under the rotor in the distributor or on the side of the oil pump drive assembly OPDA. This too is an easy fix. Bolt and a wire connector.
The symptom of a bad CPS is poor gas mileage, rough running, misfires or engine not starting.
Last edited:
Hmmm, not sure if this is my problem then. The milage is horrible 11 -12, but I do have 190k on the engine so wonder if it's simply age. Runs great, smooth, never hesitates and has never stalled. As far as starting I do have to turn the key and wait about 5 seconds then she cranks over fine. If I don't wait and crank it right away it's harder to start. Misfires, really none to speak of if you listen, but watching the needle at idle you can see it just slightly bump. Engine light stays on forever unless it's reset then after I hit 65mph it comes on solid again.
I'm still thinking valve springs as I've read, but don't want to go there if I can help it. If I did the valve springs can I just swap them out with OEM's without doing a complete rebuild of the head?
JPNinPA
Active member
Before swapping things start with some preventative maintenance.
First the turn the key and wait issue, is the valve on the fuel pump. The valve keeps the gas from bleeding back into the tank and when it fails the lines empty. When you start without waiting the lines are empty and you end up cranking until they are primed. Waiting 5 sec allows the lines to be primed. You could operate this way for years without an issue.
Watching which needle? Battery?
If so and as general maintenance you should get your battery load tested. Clean the terminals and connectors. Also look at the cables. They do corrode over time and end up become high resistance and will causes issues. Be sure to inspect and clean the ground cables. The places where the grounds connect to the body and engine need to be sanded to a shine and reconnected. Be sure your alternator is charging. At idle you should read 14.4 volts on the battery. 12.6volts with the engine off.
Clean your throttle body and IAC. Last clean the valves and cylinders. There is a method of pouring slowly about a1/2 cup of water into the TB when the engine is not and running. Manually keeping the idle up so it doesn't stall drizzle the water in over 2min. Once finished shut the engine off and for 15 min. Then start the engine and run at 2500-3000 rpm for a few min. It is ok to drive it this way. Take the RPMs above 3300 occasionally so the valves have a chance to rotate.
Also run fuel injector cleaner in your tank.
For the check engine light. What year jeep? You could do the key dance ( off to on, and off three times ending in the on position) and read the codes in the odometer or go to AZ or adv and borrow their clad reader. Post up the codes. Well give direction fro there.
Last edited:
Thanks for the reply and suggestions. Sorry it took a day or so, but a big turkey got in my way.
The Tach sitting at an idle.
Not too long ago I ran a dose of Seafoam through the valve cover, vacuum line and gas tank after a similar suggestion elsewhere. Didn't get big puffs of smoke like others have experienced. Still got the errors after a reset. I recently did an oil change and don't want to go there again unless it's absolutely necessary.
I remember back in the 80's running water through, so I'm somewhat familiar with the procedure; should I still do it after this recent dose of Seafoam that didn't make a difference If that didn't do the trick will the water?
I own a code reader and the last time I ran it this is what I got:
PO300 Random/Multiple Cylinder Misfire Detected
PO302 Cylinder 2 Misfire Detected
PO304 Cylinder 4 Misfire Detected
PO305 Cylinder 5 Misfire Detected
PO306 Cylinder 6 Misfire Detected
My Jeep is a '97, 4.0, auto.
The Tach sitting at an idle.
Not too long ago I ran a dose of Seafoam through the valve cover, vacuum line and gas tank after a similar suggestion elsewhere. Didn't get big puffs of smoke like others have experienced. Still got the errors after a reset. I recently did an oil change and don't want to go there again unless it's absolutely necessary.
I remember back in the 80's running water through, so I'm somewhat familiar with the procedure; should I still do it after this recent dose of Seafoam that didn't make a difference If that didn't do the trick will the water?
I own a code reader and the last time I ran it this is what I got:
PO300 Random/Multiple Cylinder Misfire Detected
PO302 Cylinder 2 Misfire Detected
PO304 Cylinder 4 Misfire Detected
PO305 Cylinder 5 Misfire Detected
PO306 Cylinder 6 Misfire Detected
My Jeep is a '97, 4.0, auto.
Similar threads
