What woukd cause an intermitit misfire in a cylender

Tiny
READ3056
  • MEMBER
  • 2003 MITSUBISHI ECLIPSE
  • 126,000 MILES
When the engine light comes on it reads cylender 2 misfire. I replaced the map sensor, throttle position sensor, and the fuel injectors. But at an idle the car runs good and and if I slowly apply the gas but if I hit the gas hard or fast it will mosfire and the engine light will come on. There is no vcume leaks or intake leakd. There are new plugs and wires. I switch the coils around and still cylender 2. Now last night I started to take the engine wire harness out and checked the connectioms. Put it all back together and she ran great. I went out this morning and back to the misfire now I am lost. Any one have any ideas?
Monday, October 8th, 2012 AT 12:16 AM

11 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Check the spark plug wire at the cylinder. Wiggle the injector wire harness connector to see if there are any changes. Seems like something is loose somewhere.
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Monday, October 8th, 2012 AT 1:18 AM
Tiny
READ3056
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Yea all the connectors are tight and they are all plugged in. I'm not sure why she came out of it for a little while last night but its still acting up and when it kicks the engine light on it runs 10 times worse
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Monday, October 8th, 2012 AT 3:10 AM
Tiny
READ3056
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In neutral or any gear I can slowly accelerate to any rom without issue but if I accurate kinda hard it will sputter in neutral and all the gears
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Monday, October 8th, 2012 AT 3:16 AM
Tiny
KHLOW2008
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You need to retrieve the trouble codes for the MIL indicating. Let me know the EXACT code and we shall see what needs to be done.
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Monday, October 8th, 2012 AT 3:19 AM
Tiny
READ3056
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I believe the code was p302 not sure but I looked it up and said it was misfire in cylinder 2 but I erased the code and runs better but if it gets into a bad sputter it will set the code and run 10 times worse. If I am easy on the throttle the engine light won't come on
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Monday, October 8th, 2012 AT 3:23 AM
Tiny
KHLOW2008
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Yup, a misfire in cylinder # 2. If the spark plug wires are not OEM, I would repeat my suggestion of having it checked.
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Monday, October 8th, 2012 AT 4:05 AM
Tiny
RHONDALMORGAN
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  • 1 POST
I have somewhat of the same issue - had several fault codes that called out #2 cylinder misfire -after clearing codes no light lately - but quick acceleration causes stumbling. Working through troubleshooting but haven't found any smoking guns. Currently troubleshooting injector system. Very weird symptoms.
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Sunday, October 14th, 2012 AT 1:07 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
What were the codes retrieved?
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Sunday, October 14th, 2012 AT 1:27 AM
Tiny
GREGMORGAN1
  • MEMBER
  • 1 POST
PO302. Weird thing is haven't had a code light for a while now but symptoms are getting worse. Plugs are golden tan. Electrical is in excellent condition.
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Sunday, October 14th, 2012 AT 1:59 AM
Tiny
READ3056
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My problem ended up being the boot coming off the coil on the number 2 cylinder. It threw me off cause I swapped the coils with the boots attached and it was still reading cylinder 2 misfire, but I don't think the computer cycled through to put out the new code. But I got a wire and boot set from advanced and she came out of it. But I've been driving around and my light still hasn't gone out yet, gonna have to have it checked tomorrow to see if it just didn't clear yet.
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Sunday, October 14th, 2012 AT 2:05 AM
Tiny
KHLOW2008
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If wires are non OEM, they tend to slide off the casing where you plug into the plug tubes. This would result in the wire not reaching the spark plug causing the misfiring.

Recheck the wires for snugness and ensure the wires are reacing the spark plugs. Have the coils tested and ensre you have bright blue sparks.
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Sunday, October 14th, 2012 AT 2:24 AM

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