Misfire Rough Idle--Codes P0300, P0449 and P0455 - Saturn Outlook Online Community
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post #1 of 3 (permalink) Old 05-14-2014, 09:00 AM Thread Starter
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Misfire Rough Idle--Codes P0300, P0449 and P0455

2007 Saturn Outlook

Looking for some advise before I take this to a repair shop. My car was running just fine but has had the code P0455 for over three years. I was told by onstar that it would not affect the car it just meant that it was putting out more emission than it should.

Fast forward to last week when my husband had to drive my car to work because his truck was in the shop. He said he put gas in it Monday morning and it didn't want to star and it took a few mins to get it to start. This has never happened to my car before and it was running fine the day prior. He also put gas in it again on Wends and it did the same thing. He of course doesn't tell me until Wends. I go to get in it wends to drive to town and it has a very rough idle and engine shake and can tell that it is misfiring. I contacted onstar at the time but the only code was still the P0455. The next day when I went to dry if I noticed it worse when you are not in park and have your foot on the break at a stop. The check engine light started to flash and I contacted onstar again and the two new codes of P0300 and P0449 showed up. My husband also said that one day the tracking stystem lights came on and went off. Now if he was on our dirt road when it's muddy that would have made since but he was on the highway. They have not come back on but wanted to throw that in there just in case.

Thanks for your assistance.

P.S. No I have not replaced the gas gap yet.
cowannbell is offline  
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post #2 of 3 (permalink) Old 05-14-2014, 03:28 PM
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Re: Misfire Rough Idle--Codes P0300, P0449 and P0455

To solve the P0449 & P0455 codes, have the purge valve replaced. Also, purge valve life is shortened by the practice of topping off the tank, so try not to do that after the valve is replaced.

The purge valve is #5 in the following diagram:


As for the P0300, it is a general misfire code. While replacing the purge valve can help alleviate this condition, two additional areas to look at: ignition coils & plugs, and fuel injectors. Yes, the plugs are supposed to last 100k miles, but many misfire issues have been solved by changing the coils and the plugs. As for the fuel injectors, have you ever had the injectors cleaned? They could use a cleaning if never done before.

Continually running with a mis-fire condition can shorten the life of the catalytic converters.

'09 XR, AWD, all options except rear DVD entertainment
XRDreamliner is offline  
post #3 of 3 (permalink) Old 05-14-2014, 04:19 PM
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Posts: 754
Re: Misfire Rough Idle--Codes P0300, P0449 and P0455

Originally Posted by cowannbell
car was running just fine but has had the code P0455 for over three years.

Probably why GM is doing the Airbag recall and soldering the wires vs the plug...
too many folks continue to drive and drive and drive-- while a SERVICE light has illuminated.

+1 to what XRDreamliner said....

2010 FWD LT1-Gold Mist Metallic- seats 8.<br />Build Date- July 31, 2009-2nd day of Spring Hill 2010 production.<br />2013 Equinox 3.6L -&nbsp; &nbsp; 16,755<br />2010 Traverse 3.6L-&nbsp; &nbsp; 74,300<br />2003 Trailblazer 4.2L-170,500
rbarrios is offline  

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