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Check engine light 3 times in first 6,000 miles

10K views 59 replies 15 participants last post by  Desertnate 
#1 ·
Hi everyone. I have had my '10 M3 since mid June and have had the check engine light come on 3 times due to carbon buildup on the spark plugs. Each of the previous times the dealer cleaned the plugs and turned off the light. This time I am going to have them look at it more throughly. Any ideas on an underlying reason this keeps happening?
 
#4 ·
How's your gas mileage been? Carbon deposits are generally due to an excess of fuel in the oxygen/fuel mixture. Could be a bad O2 sensor, bad fuel injector, or an issue with the computer that regulates the mix.

The dealership should be able to hook up your car to their diagnostic equipment and see what's out of whack.
 
#5 ·
Been getting very steady 29MPG since I have had the car.

The first time I took the car in the dealer cleaned the plugs and said it was due to starting and very briefly running the car and then turning it off (said this might have been done at the dealer before I got the car).

The next time it was 3000 miles later and they just cleared the light and held the car at 4,000RPM for a few minutes to burn off the carbon as they just squeaked me in between other appointments becauase they wanted to look at it quick to make sure it wasn't a bigger problem and I could still drive it.

I put the K&N air filter in from my '06 M3 about 2,000 miles ago, so I got the light twice before that was in. Never had this problem on my '06.
 
#7 ·
Thanks for the thoughts, will remember to have them check that. I have an appointment Friday afternoon to have the car looked at. Any harm in driving it until then or should I try to borrow another car?
 
#9 ·
Any harm in driving it until I get the car in for service this Friday or should I try to borrow another car?
 
#11 ·
My old car, 2002 Pontiac Grand Prix, had a thing where if the check engine light came on, the car would go into "safety mode" it would drastically cut performance as well as mpg just to make sure whatever the problem was wouldn't make the engine go KABOOM!

Anyone know if Mazda has this "feature"?
 
#13 ·
Ok thanks, oddly enough I don't really even notice much of a difference in power. Car still takes off like always.
 
#14 ·
Is the EGR the same as a PCV?

If it is, in addition to plug problems you also get pressure built up in the crank case which can cause gaskets to leak in the long run.

Also, if this is the same device, check the air cleaner to see if there is any blow back on the underside of the filter.
 
#15 ·
#16 ·
did a quick search on the two and they don't seem to be the same. something to bring up though when I take the car in. It does seem to idle a hare rough right after starting.
 
#18 ·
#23 ·
i know exactly why engine light went on, he Most likely put gas in his car and didn't twist the lid until he heard 3 clicks , that's exactly what my friend did to her car we took off the light with computer, then when she checked gas lid it wasn't twisted all the way. it even warns you that if you don't tighten it the light may go on
 
#25 ·
dont we have a lil light for the gas cap thing?
 
#27 ·
I know it's not the gas cap as all 2010 models have a seperate light for that.
 
#29 ·
indeed. Also, i have used different brands of gas, not really favoring one. Speedway, Shell, BP, Giant Eagle GetGo
 
#30 ·
We dont have Getgo's over here, but I have heard they are pretty decent from my homies in the mid and south. I always stick with either Chevron or Shell, in that order. If there is no chevron in sight, I will go to shell. THey are both super-clean gasolines, and run really well, even on regular.
 
#31 ·
I was a pretty regular Speedway user on my '06 Mazda3s Sedan and it never gave me any problems, plus the speedy rewards points are a nice bonus.
 
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