01 Cherokee 303 misfire code help

awilson

Active Member
Joined
Feb 14, 2011
Location
winston-salem
Does anyone have any suggestions how I can get the famous 303 misfire code to go away on my stock 2001 Jeep Cherokee Sport4.0 inline 6cyl and stay gone? I have changed plugs, installed the factory Jeep insulator sleeve on # 3 injector wiring,. I can clear the code, drive it for about 250 miles of normal daily driving in town driving before check the engine light comes back on with the same 303 misfire code. Any recommended Jeep mechanics who can solve this within 50 miles of Winston-Salem NC? I am new to this site and this is my 1st Jeep , any and all suggestions will be very much appreciated. Send replies to awilson@triad.rr.com please with subject 303 misfire code.

Thank you,
Allan
 
I'm a tech in GSO, not a stealership either, but let me run this by my lead tech and I'll be in touch in a bit. He's real familiar with the Jeep codes and permanant fixes. Text me every code it's shooting so we can have a look see. We use Identafix, Mitchell and should get a simple and final solution.
Jason, 865-640-9694
 
Carbon buildup on exhaust valves will cause the valve(s) to seal poorly. Also, AC compressor reed valves can cause the misfire (usually can monitor the misfire with the AC on and off). The coil tower is a usual suspect as well.
We do a lot of valve jobs on the later model 4.0's for this very issue. You can hold a dollar bill at the tailpipe when the miss is occuring. If the bill gets sucked up the pipe, you know at least one exhaust valve is not sealing.
Also, be sure to use conventional plugs, nothing fancy. Gap them at 0.035", period.
We have TSB's that direct us to rotate the exhaust valves in order to knock the carbon off. This tends to only help on lower mileage engine however.
I have seen injectors (especially #3) fail, causing an intermittant misfire.
May wanna grab a dollar bill and fashion a noid light so you can distinguish between a mechanical issue or a fuel/spark related one.
 
Thank you very much, look forward to hearing back from you. Where are you located in Greensboro, will probably bring it down to you.
Allan
 
I apologize for my dealer rip of remark and have removed it form my listing. I have just had a bad experience with a local dealer on this issue who charged me over $800.00 and still have the same issue after normal daily driving of approx 250 miles and the check engine light comes back on with same code 303, just seems this dealers techs keeps wants to try new things like they are guessing instead of fixing the problem. I did file a complaint with the owner of this dealership which was like talking to a tree. But you are exactly right, not all dealerships are rip offs and I do apologize for my remark. JUst want to find a honest mechanic who knows how to fix my issue. Thank you for your reply.
Allan
 
I have a 01xj and it runs great till I drive for a long distance and then cut it off and start it back up and it starts acting like its missfireing, & I did the dollar bill test and it does suck back up, but no check engine light? it goes away fairly quickly by its self by just letting it idle for a min, but is this the same issue? Its been doing this for awhile but hadnt really worried bout it since it fixe's itself every time.

sorry for stealing your thread but I guess this is the same issue Iv been having??

So I now no atleast one exhaust valve is not sealing?, then what, if any is a cheap fix for this?
 
LBjpXj said:
I have a 01xj and it runs great till I drive for a long distance and then cut it off and start it back up and it starts acting like its missfireing, & I did the dollar bill test and it does suck back up, but no check engine light? it goes away fairly quickly by its self by just letting it idle for a min, but is this the same issue? Its been doing this for awhile but hadnt really worried bout it since it fixe's itself every time. sorry for stealing your thread but I guess this is the same issue Iv been having??
Click to expand...

If the dollar is being sucked up the tailpipe, you have an exhaust valve that is not sealing well. It *can* come and go, here's how. People dont realize that valves also rotate as they move and and down. They will typically rotate above a certain RPM range, They can rotate to a place where they do or do not seal. Make sense?
Picture the exhaust valve that is currently not sealing. What happens on the intake stroke when there should be vacuum confined (basically) to the combustion chamber (and intake side)? That vacuum that leaks past the exhaust valve is what will cause that dollar to suck up the tailpipe. It wont do it every pulse, but only on that particular cylinder's pulse.
Sounds like you're about to pull a 4.0 cyl head...
 
Jody Treadway said:
If the dollar is being sucked up the tailpipe, you have an exhaust valve that is not sealing well. It *can* come and go, here's how. People dont realize that valves also rotate as they move and and down. They will typically rotate above a certain RPM range, They can rotate to a place where they do or do not seal. Make sense?
Picture the exhaust valve that is currently not sealing. What happens on the intake stroke when there should be vacuum confined (basically) to the combustion chamber (and intake side)? That vacuum that leaks past the exhaust valve is what will cause that dollar to suck up the tailpipe. It wont do it every pulse, but only on that particular cylinder's pulse.
Sounds like you're about to pull a 4.0 cyl head...
Click to expand...
yea it only does it now and then and only after shes good and warm and turnd off then on again....Great!!!!!!@$#^$#^$## and I just did the head gasket like 4 months ago! I looked it over really good knowing these late models have head issues and didnt see any problems, but what do I know Im just a back yard mechanic..So I need to replace the head then? Thats my only option? Thanx for Info:beer:
 
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