Misfire/Rough idle

Asked by josephbajza Jul 02, 2018 at 07:57 AM about the 1999 Jeep Grand Cherokee Laredo 4WD

Question type: Maintenance & Repair

I have a 99 Grand Cherokee. Recently I replaced the head gasket and took
the head to the shop for valve job and resurface job. While in there I
replaced the Lifters, Push rods, rocker arms, timing chain, water pump,
Spark plugs, and radiator. After getting it all back together there seems to be
a misfire and it runs rough. No check engine light unless I drive it for about 5
miles. The check engine light came on and was for multiple misfire, and
misfire cylinder 4 and 6. Since that time I have replaced the injectors,fuel
filter, crank Position sensor, I checked the injector plugs with a noid light, No
problems, I checked the coil pack with spark tester, No problems. I
rechecked the time gears, and they appear to be lined up. I did a
compression test and #3 was at about 135, and all other cylinders were at
150. I'm not sure what else to check.  

1 Answer
3,100

SubaruTech5862 answered 6 years ago

O2 sensors mass air flow but leaning towards O2 because of you saying you have to drive it before it does it so maybe once your Cat is hot enough it doesnt read properly and thinks it's running to lean or rich and I would just replace your coil pack because you've done everything else just because it tested fine once doesn't mean it is.

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