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A misfire. 30,000 on the engine. It is random. 2002 Jeep…

Customer Question
30,000 on the engine...

30,000 on the engine. It is random

Mechanic's Assistant: What is the model/year of your Jeep?

2002 Jeep Grand Cherokee, 4.7

Mechanic's Assistant: Are you fixing your Grand Cherokee yourself? What have you tried so far?

Yes, I am doing it myself

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

I have replaced the spark plug, ignition coil and injector. Still getting a P0301 code

Submitted: 7 months ago.Category: Jeep
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Customer reply replied 7 months ago
I have also check power to the ignition coil and checked for a ground signal to the injector, both checked out fine. I swapped the ignition coil from cylinder #1 to cylinder #2, and the code stayed on cylinder 1. Also, while the engine was running, I unplugged the coil to cylinder #1 and it made no difference in the running quality, almost like the cylinder is completely dead. I can clear the code and drive and the CEL light does not return until the next time I start the vehicle. The CEL is solid, no flashing. So it's almost like it is intermittent, but I can tell it is running a bit sluggish all the time.
Answered in 1 hour by:
12/5/2017
Jeep Mechanic: Mechanic01, ASE Certified Technician replied 7 months ago
Mechanic01
Mechanic01, ASE Certified Technician
Category: Jeep
Satisfied Customers: 3,290
Experience: Owner at Baltic investments
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Hello my name is ***** ***** welcome to just answers! I will be assisting you with all of your vehicle questions today. Give me one moment while I review your question and come back with a answer. Please be aware I do not know your skill level or abilities so I will be asking a lot of questions and in a lot of cases we will respond to each other quite a lot before we find a solution. As far as phone calls are concerned that is the system prompting you, not me, and they do cost more money, I prefer text but in some cases a phone call is required. If I don’t answer right away or quickly in conversation I am helping another customer or have stepped out for a moment and will respond as soon as I can. Ok lets get started!

So I would suspect a problem with the valve spring, valve or rocker arm or maybe even borderline bad compression.

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Customer reply replied 7 months ago
I would tend to agree with you, but I believe if it were a mechanical issue such as a fallen ticket arm, the CEL would trigger immediately and the misfire would be constant, right?
Jeep Mechanic: Mechanic01, ASE Certified Technician replied 7 months ago

not always, if there is just slight play in it it would be interment, best would be to pull the valve cover and inspect

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Customer reply replied 7 months ago
Okay, I'll pull the valve cover and let you know what I find. Keep in mind, I had the motor rebuilt 30k miles ago, so it's still fresh. Cheers!
Jeep Mechanic: Mechanic01, ASE Certified Technician replied 7 months ago

also check compression too make sure thats ok

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Customer reply replied 7 months ago
I was going to go ahead and perform a compression test anyways, just to check in case there was a bent valve. I will let you know the results.
Jeep Mechanic: Mechanic01, ASE Certified Technician replied 7 months ago

sounds good ill be around today

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Jeep Mechanic: Mechanic01, ASE Certified Technician replied 7 months ago

Please let me know if you have any more questions.
Customer satisfaction is my number one goal. Giving me nothing less than a 5 star rating would be appreciated very much. You can do this rating at the box on the upper right hand corner. This will not close our chat session and at no extra charge we will still be able to talk about any other issues you may have for free! Providing a rating is the only way I will receive credit for my work with you. Negative ratings do not result in a refund so If you’re not satisfied with the work we have done so far please respond more and let’s get your question figured out. Thanks Shawn!

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