Stuttering at idle when cold, threw misfire code

Hi everyone,

I have a relatively new-to-me automatic 2007 Mazda 5 with about 210,000km on it. I had it inspected by a mechanic when I bought it in December and they deemed the engine/transmission to be in good shape and only noted problems with rotors and rear shocks - both of which the dealer replaced.

I've been having some problems lately with the engine stuttering at idle when cold. If I'm at a traffic light the engine will idle rough, almost as if it could stall, every few seconds. It only does this when it's been started from being very cold and the condition lasts about 5-10 minutes then it's good to go and drives normally. It threw a code for the first time (P0301 cyl 1 misfire) about two weeks ago but it was extremely cold out so I dismissed it. It threw the same code again yesterday although it was much warmer.

I've seen talk of a recall/software update that might be related? I don't know if it would have been done on this car. I've also noticed some people suggesting spark plugs could cause this type of a condition. What should I start with to try to solve the problem?

Thanks!

Have you got it figured out, yet?

If that would have happened to me, I would have installed a set of plugs as the first step. If that didn't get rid of it, I'd swap the spark plug coils between cylinders #1 and #2 and see if the code changed from cylinder #1 to #2.

Thanks for the suggestion! I was out of town for the last week so didn't have a chance to look much further into it but I'll try this. It seems like most people prefer to just get the OEM plugs from the dealer so I'll phone them during the week when the parts department is open and check on pricing.

New spark plugs did the trick! Took a little wrestling but got the old ones out and the #1 plug was particularly rough looking (see below). Anyways, the cars running as normal again - thanks for the help!

Gotta love a simple fix! Nice.

FiftySix said:

Gotta love a simple fix! Nice.

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Even better when it's cheap too.

pnambic said:

Even better when it's cheap too.

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I got a pretty good deal too. I checked my receipt later and realized that they only charged me for 1 spark plug!

OxnardMontalvo said:

I got a pretty good deal too. I checked my receipt later and realized that they only charged me for 1 spark plug!

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That's why Canadians have a reputatiopn for being so nice...giving away spark plugs and whatnot.
And if you went back to let them know about it, they'd probably apologize for it too.