Ive had a horrible misfire on cylinder 6. when it happens the car will drive horrible. The wierd thing is is that it keeps coming and going.I can drive for 30 miles and it be fine then the next 10 or so willbe horrible then it will be fine again. Ive had it looked at already and couldnt really fine a problem. We narrowed it down to a valvetrain problem and gave it a complete valve job and swapped the lifters in that cylinder. It ran fine for a day then started doing the same thing all over again.. Does anyone have any ideas because out of a mechanic, myself, my dad, and another mechanic have no idea... Any help woud be great!

 

Aparently it wasn't the valve train so here's some things to try, one at a time.

swap the plug wire with another cylinder
swap the plug with another cylinder
swap the coil with another cylinder
swap the injector with another cylinder

if any of these causes the misfire to move then you've found your demon.

 

That was the first thing we tried before doing any of the major work....

 

Try doing these things again , whether you want to or not , just to double check . It almost has to be one of these things , unless your rocker arm went which should have been noticed when you had the heads off , or a broken valve spring which would have been noticed when it was apart , an extremely worn guide which would have been noticed when the valve job was done , or a broken ring which would most likley cause some smoke to come out of the dipstick tube while the engine is running if you pull the dipstick out . Just my .02 .

Mike

 

I had a bad misfire on my motor on cyc #7 and 3 weeks later I realized it was the headgasket.