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Dave, Jeep Master Tech
Category: Jeep
Satisfied Customers: 1158
Experience:  Chrysler Triple Master, ASE master Tech AA degree in Auto.
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Jeep Grand Cherokee Laredo 2000 jeep 4.7 random cylinder misfire

Customer Question

2000 jeep 4.7 random cylinder misfire changed plugs checked compression on all cylinders all 145 lbs cylinders 1-3-5-7-2-6 all looked carbon fouled #4&8 are still clean i checked fuel pressure and fuel injectors all are fireing what else should i check
Submitted: 6 years ago.
Category: Jeep
Expert:  Dave replied 6 years ago.

Dave :

Hi, we have had a lot of the 4.7L engines having multiple cylinder misfires due to burnt valves. Even with good compression you can still have a burnt valve causing the problem. The only way to know for sure is to do a cylinder leakdown test. That is a test that needs a special piece of equipment and air from a compressor. You fill the cobostion chamber with air and watch a gage and see if it holds the air or if it leaks down. If it leaks down then wither one of the valves or the rings are bad. We have also had issues with the cam and crank sensors going bad and not setting any codes, either one of them can cause the problem so we replace both at the same time. Use only Mopar sensors as we have had nothing but problems with customeers coming in after they have replacved a sensor with an after market one. Also if the flywheel has gotten dinged, bent or cracked it will cause the crank sensor to get the wrong information and cause misfires but this is way rare.

Customer :

i,ll check it tomorrow and get back with you thanks

Dave :

sounds good, let me know