I have a 2002 3.9L with a misfire cyl4. I changed the cap, rotter, plugs, and wires not too long ago. Changed the wire and plug again the cap still looks brand new. I put the wire next to the plug and it's getting good spark. I tried the carb cleaner on the manifold to see if there was a leak and no change in the idle and I don't see any vacuum hoses messed up. Whats next??? Thinking of changing the injector. When i pulled the plug to look at it it smells like raw fuel too if that can help some one let me know what they think. and also it has more of a ruff idle after driving it on the freeway. cold starts idles fine in tell i drive it a few miles

 

It very well could be a dirty/bad fuel injector.

 

Could be a bad O2 sensor as well... I had the backfire from hell which after changing everything turned out to be my bank 1 sensor 1 O2.

 

Do a complete compression test that means pull all the spark plugs and record compression on each one. I am in the process myself of a lifter change and gaskets I will be checking push rods,rocker arms. I have cyl#5 it is not totally dead but enough to cause a misfire. I did all the other stuff injector etc.

 

I never thought of that. I have a compression tester never used it on the truck. kind of scared to see how bad it is because it does burn oil with 175,000 miles and i cant remember which plug gets real bad but i want to say it is #4 I didn't think a little oil burning would have cause a misfire. Too much oil builds up on the plug then i would change it and every thing would be good. It cant be too bad just passed smog. ill check the compression any ways just hopping it's not so low thats going to cause more prob then just a misfire

 

I have 150k on mine and I have had this truck since new with oil changes and all maintenance required. I am still changing the lifters I have everything to do so. I did take a scope camera and check the cylinder. Once I get the valve cover off today I will and see if something is broke. The funny thing is that no noise in the valve train. One more thing take off the air cleaner and look down the throttle body and see if there is alot of oil. The gasket on the bottom of the intake manifold known to go away. Reman heads are $500. I will do a leak down test on that cylinder.

 

i never looked down into the t body but when i take off the air cleaner it smells pretty bad of burnt oil. im off today so ill be checking some things out in between pulling apart my steering column to put in a new ignition on my 72 nova and an oil change on the wife's jeep patriot. going to be a whole day of working on cars

 

My spark plugs looked good. The chevy should be easy either way. The switch down the column a plug a few screws unless you are changing the key cylinder. Your dodge does it consume a lot of oil? Oil on the bottom of the intake or stuck PCV valve. Well I have the valve cover off nothing broken.