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My Kia is misfiring on cylinder 4 after it is driven for quite a while. New coil packs last year, plugs, wires, did plugs again last week. It runs good cold, so I didn't think it would be the injectors. I replaced the ECM, ran great for a week. Today was real hot, and it started misfiring again. It ran fine to dinner and back, and then I let it rest for 20 minutes and went to drive and ran horrible. I know that it wasn't a fuel pump issue, but I wanted to replace it before it left me stranded, 200,000 miles now. I cleaned the heck out of the throttle body, mass air flow sensor and I installed new O2 sensors weeks before this began. I ran a compression test and it was good and even. I swapped coil, wire/boot and plug from 4 to 2 and it still came back as #4 misfire after I reset it. It took a week to come back the first time. After that I changed the plugs, just for safe measure. It only does this on real hot days, and usually after it has been driven for a while. This has now been going on for about a month. The weather cooled down and I changed the ECM as the last thing. Ran really good for like a week now, probably until it learned the system...Any thoughts would be great.
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Did you change the spark plugs and correctly gap them?
Swap the coil and plug from cylinder 4 to cylinder 1 and see if the misfire moves to 1.
If it does move, then the coil or spark plug is bad. Then you can swap the coil from cylinder 1 to cylinder 2 and if the misfire moves, you know it is the coil.
It is possible that you may have two coil packs going bad as cylinders 3 and 5 are on different packs. To attempt to prove this without going broke, you could swap the 1/4 coil pack with one of the other two and see if the misfire changes the 1 or 4 cylinder instead. If it does, you have the issue resolved. See the diagram below for more details.
If you can't read the coil packs on the right, they are paired from top to bottom as 3/6, 2/5, and 1/4
Jeep Liberty Check Engine Light/Misfire Due to Intake Valve Locks/Valves. ...Misfire cyc 4 and random cyc misfires, changed coil packs and plugs... sounds as if rod ... Light came on again (misfire on cylinder 4) - switched coil from 4 to 2. Light ...
CarGurusMay 27, 2009 - #4 misfire new plugs and coil pack on #4 light came back on after 300 miles if ... How come it stopped misfiring for 2-3 months, and now is back? ... I have a 2005 Jeep Liberty 6 cylinder, engine light came on scaned the codes ...
the orer of the cyls from front to back 1 first 2 second 3 third and the last at the windshield is 4 so you should have a coil on 2 or 1 and the wire goes to plug as well 3 and 4 have a coil and a wire somes times the plugs are the problem but check the coils while your there
The injector is bad , internal coil when heated shorts out . Feel lucky it's only one injector . It could be like this corvette all injectors Quit when hot ! Test the injector with ohm meter . Chevy Corvette No Start When Hot The Diagnosis
if you started out with no misfire at all and then got a misfire after the tune up that does seem strange, my best guess would be that the plugs are not gapped correctly or the spark plug wire is, not completely snapped on, or the wire on the 4th cylinder was damaged when it was removed, i would start out making sure all the wires are on, you will either hear of feel a small snap when the wire is seated on the plug good, also make sure the wire is connected to the coil good
If you can't read the coil packs on the right, they are paired from top to bottom as 3/6, 2/5, and 1/4
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