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Old 08-14-2015, 01:37 PM
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2002 jeep grand cherokee p0300 multiple cylinder misfire

Its got the 4.7 v8 125k miles...it started throwing this code occasionally, at high rpm 4k & now more often. Also it seems to happen more severely with the a/c on going uphill, it also throws individual cylinder misfire codes it started with cylinder 4, then 4&7 now 4, 7, 2, 6, it starts great runs good until I get to higher revs.

So I have changed the spark plugs I went with champion double platinum & I have ruled out the coils by replacing cylinder 7 & still get the code for 7

Any Ideas where to go from here?

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Old 08-14-2015, 09:34 PM
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Re: 2002 jeep grand cherokee p0300 multiple cylinder misfire

It also threw trany code p1793 loss of torque management system
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Old 08-14-2015, 09:39 PM
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Re: 2002 jeep grand cherokee p0300 multiple cylinder misfire

Yes, to start by posting under the right section. Here is the WK section.
There are several possibilities which can cause misfires. It can be cylinder related, but in your case its a random misfire, so some options will not apply.
This engine doesn´t like fancy plugs, use only the standard copper core plugs.
Then i would have a look at the O2 sensor readings and see what the STFT (short term fuel trim) figures do. You will need a scanner with live data possibility, or a smartphone with bluetooth or wifi dongle and the free Torque app.
A too rich or a too lean mixture can cause misfires. Since the misfires happens on both banks, i would not expect an individual O2 sensor, its more probably a common thing for both banks. A MAP sensor for example. But it would be interresting to see what the STFT´s are showing for both banks. Single digit figures are normal (under constant throttle), but when it goes over + or - 10 it normally means that something is going on.
Also possible is sticking exhaust valves due to carbon buildup on the stems, eventhough i wonder if using AC or not would make any difference. For this a seafoam treatment through the brake booster line would help.
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Old 08-14-2015, 09:44 PM
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Re: 2002 jeep grand cherokee p0300 multiple cylinder misfire

I just realized that I posted in the wk forum I just reposted in the wj thanks for the info today it ran great do you think I should change the plugs back to coppers
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Old 08-14-2015, 09:46 PM
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Re: 2002 jeep grand cherokee p0300 multiple cylinder misfire

Also the plugs I replaced were very worn out but clean exept for a little white residue
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Old 08-14-2015, 10:04 PM
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Re: 2002 jeep grand cherokee p0300 multiple cylinder misfire

Some people seem to run other then copper plugs, but i heard that they can give problems. You can first to try to rule out any other possibility, or just change them and be sure its (not) that.
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