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2001 Mitsubishi Eclipse Runs rough

Tiny
WESWINS
  • MEMBER
  • 2001 MITSUBISHI ECLIPSE
  • 2.4L
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 160,000 MILES
Car runs rough in drive not so much in park.I have changed the following upstream O2 sensor, plugs gaped correctly, plug wires set of 2 also 2 ignition coils. After all this was done the check engine light turned off car ran good for 50 miles then light comes on and rough again.I did notice a little oil on top of spark plug boot, 2 plugs looked black on end(remember o2 sensor done)not seeing oil on bottom of spark plug boot also must mention valve cover gasket and spark plug rubber rings that you get with kit were new. Timing belt also new. Could it be computer, injectors?Back to top why would it run better in neutral and park than drive?Giving up on this car pleas help. Thank you.
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Saturday, June 20th, 2015 AT 10:15 AM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
You have a simple misfire. Misfiring engines always run rougher when under load. In "park" they can easily coast along so you won't feel the misfire as much.

Oxygen sensors don't cause misfires. They simply report on what has already taken place inside the cylinders. The place to start is by reading and recording the diagnostic fault code(s). Chances are there is at least one code indicating which cylinder is misfiring. Once you know that, you can switch spark plugs and injectors between other cylinders, erase the fault codes, then see if new codes set for the cylinders you moved the parts to.
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Saturday, June 20th, 2015 AT 7:33 PM

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