P0300 - Random Misfire - RESOLVED

Devast8sjl

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2003 Buick LeSabre
So for a few weeks the random misfire my '03 LeSabre was exhibiting was a bit of a mystery for not only myself but 2 different shops and about 15+ ASE tech hours.

I went through all the basics of everything I read on this forum, other GM forums, or just about anything that would come up on a search. Plugs, wires, voltage tests, ohm tests, vacuum tests, pressure tests, cleaning sensors, checking grounding......the list goes on.

The first shop ran the car through a similar gambit of testing and scanning with their SnapOn scanner plus doing fuel system flushing and fuel flow tests, and even swapping a couple of the basic spare parts they had on the shelf to rule them out. After 2 days and about 6 labor hours, they said 'we can't fix it..'

They recommended another local shop that they send the problem children that they can't figure out to. These guys have a GM tech 2 scanner, so everyone figured no problem, in a couple hours or less they'd have this issue nailed down. Again, 2 days later and about 8 hours of tech time they finally took their best "guess" and grabbed a used PCM at the local car recycle center, reprogrammed it and bang, the car runs like new again. Of course there were some posts that I read speaking of this issue, but I wouldn't have ever gone that route due to the expense it would have taken based on a hunch.

I've had the car back a few weeks now and it has run flawlessly. We've driven it several hundred miles without issue. I won't claim to be an auto tech of any sort but I am still a little dismayed at how this car stumped these guys with way more experience and advanced tools than I would ever dream to have, and ended up taking a best guess to fix it. All and all, if this fixes the car in the long run, I've made out like a bandit. The first shop charged me nothing since they couldn't figure it out, and the second shop only charged me for the used part, programming and a few hours of labor. Good times.:headbang:
 
That's good news Devast8 - sometimes it just takes not letting go of a problem until you get to the bottom of it.

Those were some good saves as far as shop hours are concerned. I'm not sure most shops would have been so generous - that speaks well to your shops integrity.

Now you can look forward to many miles of trouble free driving.
 
Thanks for sharing! That could help someone out in the future. Sometimes these little electronic gremlins cause some pretty substantial problems in a car that actually has nothing mechanically wrong! If you think they will care, you might want to advise shop #1 what the problem ended up being. Maybe that info will stick in one of their mechanic's minds the next time another customer comes in with similar symptoms.
 
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