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Roadside Jerry
Roadside Jerry, Mechanic
Category: Jeep
Satisfied Customers: 2948
Experience:  40 years experience,fixing all type vehicles
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2001 Jeep Cherokee: cold start..rough idles and I get a misfire at #6

Customer Question

2001 Jeep Cherokee. Hard cold start, then it rough idles and I get a misfire at #6. This misfire persists until I turn the engine off and restart. When the engine is restarted it runs fine. This happens intermittently, only on cold starts.
Submitted: 7 years ago.
Category: Jeep
Expert:  Roadside Jerry replied 7 years ago.

Hi, finding a problem like this,without throwing parts in can take quite a bit of diagnostic time,even with all the proper testing tools. One possibility is a valve lifter holding a valves partially open.I am sending you a link to a video,this is a case study of a problem that sounds similar to yours,clink on the link,then watch and listen to what was done and what finally solved the problem. I believe you will find it interesting,and may help you diagnose your Jeeps miss.

Edited by Roadside Jerry on 10/2/2009 at 1:50 AM EST
Customer: replied 7 years ago.

I agree with the possiblity, however, that would suggest that this happens everytime I cold start. That is not the case. I will cold start lets say 20 times and it will not happen, but on the 21 it will. Then as soon as I shut the car off and restart the problem self resolves. It is intermittent... and kinda like a fuel pressure issue. what I can not understand is the relation to the hard cold start, the subsequent missfire, and then the self resolve on the immediate shut down and restart. It is almost as if the computer is at play in some way.

Expert:  Roadside Jerry replied 7 years ago.
Hi, if a lifter is the problem,the reason for the miss being intermitent is that the lifter will only be able to hold the open the valve ,if the when the engine is shut off, the valve with that the problem lifter, was in the closed position, no tension on it, then when the engine is started and the oil pressure enters the valve lifter it stays in the fully exteded position,and reduces the valve clearence holding the valve open,creating a misfire. When the engine is shut down and that valve is in the open postion, pressure on the lifter,the lifter will bleed down,and on start up won't pump up. This is just an idea I am throwing out to you,I am not suggesting you replace any parts untill you check all possibilites.