3.7L Misfire - JeepForum.com
 
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post #1 of 9 Old 11-13-2019, 10:54 AM Thread Starter
stevedenali
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3.7L Misfire

Hi,
I have a 2005 Jeep Grand Cherokee 3.7L. It misfires only on cylinder 2(passenger front). I have put new plugs in it, swapped the coils around, put a new coil pack on cylinder 2, done a new Bosch fuel injector, and took off the valve cover to make sure all looked good and it looked fine under there. I did a compression test as a last resort and compression was good. Throttle body is clean and all other typical causes of a misfire have been checked off. The car has just over 85,000 miles on it. It misfires more at idle than in the high rpms if you watch the live data on a scanner and the misfire is much worse in the cold(check engine light flashes sometimes only in winter). I believe the computer was replaced before I purchased it because my Autel scanner says it has 130,000 miles on it and the odometer says 85,000 and the car fax lines up with what the odometer says. I am at a loss here. Any help would be greatly appreciated! Thank you!


Last edited by stevedenali; 11-14-2019 at 07:11 PM.
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post #2 of 9 Old 11-13-2019, 01:01 PM
pshivers
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Have you done a compression check?

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post #3 of 9 Old 11-14-2019, 07:10 PM Thread Starter
stevedenali
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Originally Posted by pshivers View Post
Have you done a compression check?

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I should have mentioned that. Yes I have good compression! Thanks!
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post #4 of 9 Old 11-14-2019, 08:41 PM
pshivers
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If you can watch the live data, what are the fuel trims at idle cold and warm and at 3000rpms cold and warm? Thinking intake gasket leak made worse by the cold temps with the metal shrinking.

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post #5 of 9 Old 11-19-2019, 03:16 PM Thread Starter
stevedenali
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Quote:
Originally Posted by pshivers View Post
If you can watch the live data, what are the fuel trims at idle cold and warm and at 3000rpms cold and warm? Thinking intake gasket leak made worse by the cold temps with the metal shrinking.

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Sorry it took so long to get back to you. For some reason my scanner appears to do most everything else except for the Fuel Trims. I think I am going to do the intake gaskets anyways considering how cheap they are. I think I have gone through every other cause. Thanks!
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post #6 of 9 Old 03-31-2020, 06:37 AM Thread Starter
stevedenali
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It has been a long time since I have posted on this. Verified the computer was not replaced and is original. I replaced the fuel injector with a new Bosch one and still no difference. I then changed out the intake gaskets and torqued everything to spec and it changed nothing. I looked in at the intake valve while the intake was off and it looked clean and normal. It is a really strange problem. I have a special test light kit to make sure that the injector and coil pack connectors are getting adequate even power and the light will pulse with the voltage. Both tests on the injector and coil connector appeared even and normal, so that rules out a computer and wiring issue. Now, I am really confused. Any help would be great thanks!
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post #7 of 9 Old 03-31-2020, 07:38 AM
Freedome04
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pull the spark plug and check the color of the plug to some of the others.At this point all I can think of is a small coolant leak into the cylinder while sitting over night.

2004 WJ Overland Freedom 4.7 H.O 156,000
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post #8 of 9 Old 03-31-2020, 10:22 AM Thread Starter
stevedenali
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I have pulled the plug, dark brown with a little black on it from the fuel not burning off. No white. Thanks.
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post #9 of 9 Old 03-31-2020, 01:05 PM
jtec
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Some thiughts - free and easy esp with a scanner

you are seeing a p0302?
the engine is reaching correct ECT @220?
What is o2 reading B2S1?
When head was off - did #2 chamber look cleaner than others?
What plugs are you using? ZFR6F - 11G (NGK) solid copper core

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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