Misfire P0300

Tiny
GJEWELL
  • MEMBER
  • 1996 CHEVROLET CAVALIER
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 86,600 MILES
1996 Chevy Cavalier LS (2.4 dohc)
This problem first occured 2 months ago but may not be related, at that time I replaced the spark plugs, boots and a coil but it ended up being the coil housing.
The 'same' problem reoccured 'Random Multiple Misfire code P0300' this time I replaced the other coil, I.C.M. And coil housing again, I also checked the injectors and replaced their seals to no avail.
I have however noticed that the top of Catalitic Converter and the area around the rear oxygen sensor is glowing red after about a mile or 2 drive, is this a difinitive conformation that the C.C. Is bad/blocked or just a result of unburned fuel created by the misfire?
I released the the exhaust at the joint behind the sensor and it was a little (not much) louder, I was expecting a lot louder, and it was still glowing after a mile or 2.
The only other things that mistify me are that I tried taking out the fuel pump fuse and there was no difference in performance and the fuel pressure regulator is discoloured but I don't have a fuel pressure guage to check it.
I did get a compression tester 2 months ago and it checked O.K.
The car has 86k on it and has been very reliable until this.
Monday, November 29th, 2010 AT 12:01 AM

1 Reply

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
The converter may be blocked. Check your vacuum at idle if it's around 15" then it may be blocked. The misfire can be low fuel pressure, vacuum leak, compression as well as ignition problem.
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Monday, November 29th, 2010 AT 12:13 AM

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