Random misfire

fastmazdams3

Member
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09 MS3 black
I was driving home the other night and was ripping on her pretty hard, I did a shift at about 6200 rpm and the CEL came on. The car still ran fine, but i took it easy on her the rest of the way. I scanned it when I got home and it was a random misfire code. I figured it was just something wacky with the pcm, so I cleared it and its been good for now. I was just wondering if anyone else had this happen when they did high rpm shifts. If it comes on again I'll take it to mazda since its still well within warranty and I have zero mods atm. I don't remember seeing a service bulletin on this either.
 
happened to me once too, when I hit a truck rut under hard acceleration/shifting and rang the rev limiter. Cleared code and no recurrence.
 
It's happened to me as well after I installed my Injen intake. I figured it was from me screwing up the install, but the car runs smooth so I wasn't sure. I haven't taken it to the dealer for it yet and was debating whether or not I would.
 
I wouldn't worry to much about it, if it ran fine even after the CEL then eh, clear it and forget it. Only worry if it comes back.
 
Check your spark plugs. You might have some build-up on one of em.
 
Funny thing is I never changed my plugs until just a week ago and I have 31k on the odo.. man after the change to ITV22's the thing runs like a monster, no more slug however it does suck ALOT more gas now and I don't go into boost that much.(naughty)


I'll check the plugs Monday at work, its only has 14k on it so I doubt that's it but I'll find out.
 
The CEL is supposed to go off after few (3 I beleive) consecutive runs without a problem. If it doesn't, then I would start checking things like spark plugs, wires, etc. Sometimes a bad batch of fuel is enough to make it happen.

From what I see you already cleared it. I wouldn't be bothered unless it comes back soon.
 
Thats interesting, I have never heard that before 3x?



The CEL is supposed to go off after few (3 I beleive) consecutive runs without a problem. If it doesn't, then I would start checking things like spark plugs, wires, etc. Sometimes a bad batch of fuel is enough to make it happen.

From what I see you already cleared it. I wouldn't be bothered unless it comes back soon.
 
Same issue, full/high boost = random misfires

My engine is stock except for a COBB SF Intake.

I store my MS3 over the winter (2nd winter now) and yes, she’s fully winterized. This time around everything went south about 1/2 way into the second tank of gas when I resurrected her this spring.

Basically I started to feel a single hesitation at around 3200rpm. Over the course of a few hundred miles it became a lean backfire at high boost around 4-4500rpm. Then it started randomly throwing P2187 and a solid CEL. After three "clean" drives the CEL would go out. As soon as the CEL went out, the next drive or two would produce the problem and the cycle would start all over again. I put the stock air box back on and still had the issue though it became rather infrequent. I also cleaned the MAF sensor and the COBB air filter, and replaced the stock as well. This went on for 3 weeks, before I was finally able to get in and have her looked at by the dealership. Of course driving her like a granny and keeping off boost as much as possible during that time proved to produce zero problems.

Brown's Mazda in VA told me the P2187 was caused by a faulty purge valve. I had this replaced and drove her for a week. She still produced the same symptoms but only twice.

I put the COBB intake back on a few days ago, cleaned the MAF sensor again and she produced the symptoms more frequently, but since the purge valve replacement, no CEL, no codes. Then this happened...

The other night, after two drives that day with no issues I took her out and opened her up. This time, as soon as I got my foot in her (5Kish rpms,) she had multiple misfires (that I felt and heard,) a huge lean backfire, a blinking CEL (obviously from the misfires) that went solid and then limited boost. Limped home, pulled the codes and got P0300, P2187 and P0300.

I'm at a freaking loss and currently looking for a different dealer to take her to.

If anyone has any suggestions, give me a holler...next steps for me are new MAF and new EGR (maybe)...
 
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mine wasn't as harsh as Ambersand, but I threw that P0300 CEL today. On my way back from work, I did some spirited driving on the highway. The CEL went on when I shifted from 5th to 6th.
I stopped by the local Advance Auto Parts and asked them for a CEL check. He said P0300 random misfire from cylinders. He asked if I had changed the sparkplugs or anything like that.
I'm getting close to 30k and still on stock plugs, so I'm thinking they might be getting old and have some buildup around them.
The car runs fine, it doesnt seem to be doing anything different then usuall. I cleared the CEL drove around for a bit, hit up the highway for some more spirited driving and the CEL didn't come back. If it does, I'm sure I will need to replace the spark plugs.
 
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