Mechanics

P0300 CODE

2004 Cadillac Deville

Engine Performance problem
2004 Cadillac Deville V8 Front Wheel Drive Automatic 120000 miles

I have a 2004 Cadillac deville that has the P0300 code and flashing check engine light on it was missing and sputtering. I narrowed it down to what I thought was spark plugs and 2 bad coils, changed them and it helped for awhile (about two miles). Now it is missing again and has the flashing check engine light and po300 code again I checked for vacuum leaks and didnt find any. I checked for bad connections and didnt find any. I checked the EGR valve to see if it was stuck or blocked and it is fine also. And the exhaust smells rich, but not like rotten eggs. I also had a new fuel pump and filters installed about 6000 miles ago. I also narrowed it down to cylinder #7 on the scan tool and the cylinder seems to be dead and completlely misfiring, I then swapped fuel injectors on #7 with 6 and #7 still is misfiring. I put a new ignition coil on # 7 cylinder also. I also checked compression and it was fine. I checked for spark and it was good, Any Ideas? Ignition module? Crank sensor? Cam sensor? Bad wiring harness? It is running very rich also.
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Chris2363
May 16, 2010.




A random misfire P0300 normally is caused by vacuum leaks and bad fuel

Tiny
Rasmataz
May 16, 2010.
I sprayed carb cleaner everywhere, all around the hoses, boots, intake and fuel injectors, checked all the hoses, and nothing changed. Does water work better for checking for vacuum leaks?

Tiny
Chris2363
May 16, 2010.
Carb cleaner or WD40 will do when you hit the leak the engine will run smooth indicating where the leak is-You could also use a vacuum/pressure tester
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Tiny
Rasmataz
May 16, 2010.
Im having the same problem right now and I would be interested in what you find Chris im getting a rich exhaust smell and I currently drive a 2004 cadillac deville with 67k miles and i've checked for leaks and pressure and nothing yet I got the same code p0300 and it doesn't seem to be misfiring im thinking it could be one of my spark plugs I found a bit of moisture by one of them but I cant be sure any advice?

Tiny
Tjayphilly
Nov 9, 2011.

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