Engine missing/backfiring on acceleration

[jcolman]

I just had my 07 in the shop (local oil change place, not a Mazda shop) for a 60k fluid change yesterday. The mechanic also performed a "tune up" and by that I think all he did was replace the plugs. I'll have to double check. Anyway, The car drove fine yesterday and this morning. Tonight, on my way home from work, I was accelerating on the interstate and the engine started missfiring and blowing puffs of brown/grey smoke out the tailpipe. I backed off the throttle and cruised home. The car ran fine the rest of the way, only missfiring once under acceleration. I plan on taking the car back to the shop and have them look at it. I would like to have some idea of what may be causing the problem before I go in.

Thoughts??

 

[chimmike]

spark plugs. Do it yourself. Make sure they're either denso or ngk iridiums, and make sure they're gapped at .028".

 

[jcolman]

Thanks mike. I'll pull them myself and check the brand and gap.

 

[MSMS3]

I'll bet the mechanic put in NGK iridium plugs. They are great and that is what I run. But they come in the box gapped .044" and need to be gapped down to .028. You are probably experiencing boost induced spark blow out. Correct gap will fix that.

 

[jcolman]

I'll bet the mechanic put in NGK iridium plugs. They are great and that is what I run. But they come in the box gapped .044" and need to be gapped down to .028. You are probably experiencing boost induced spark blow out. Correct gap will fix that.

That is exactly what the problem turned out to be. Good call.

 

[chimmike]

Another good reason to do your own work on this car, shops don't look things up/assume.