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Old 02-27-2016, 04:05 PM
Mopar_Mikey Mopar_Mikey is offline
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Join Date: Mar 2008
Location: Parker Colorado
Posts: 1
Default Chrysler 300M Misfire issue

Hey all,
I'm getting a p0303 and car idles rough. This car is a 2001 Chrysler 300m with 185000 miles on it. It's a 3.5l like every other 300m.
Spark is good so I did a compression test and it's giving me good on all but the #3 as listed below:
Cyl 6000' Sea Level
1 135 161
2 130 155
3 60 71 Wet test 70 or 83 at sea level
4 140 167
5 130 155
6 135 161
I'm pretty certain I have a valve issue with the #3. Rings are not suspect to me since the wet test only brought it up about 10PSI. Overall the compression seems good for a car with 185000 on it.
So far I have done combustion chamber cleaning using the methanol/water cleaning, Seafoam, and the Mopar combustion chamber cleaner with no results....I had the stuff in the garage so thought what the heck, before I pull the head I'd try it.

A little background on the car. I bought it 2 years ago and did a bunch of work on it to get it up to my standards and comfort level. Before I had a chance to change the timing belt it snapped and I took a chance and changed it...already had the kit in the garage. Fired right up after that with no missing and ran great for about 12-15000 miles.
About 2 months ago the CEL came on...my son had put most of those miles on it I only drive it maybe 30 miles a month.
I now have to dig into it to get emissions done on it.
Any suggestions?
I do not have a leakdow tester and no auto parts stores seem to rent them anymore.
I have been contemplating doing the rope test to see if I can free the valve. I do have a bottle of Marvels in the garage....just really don't want to have to pull the head! Really hoping it's not a bent valve.
Any help would be appreciated!
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