codes, codes, codes (help a newb)

j-dizzle

Member
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2002 Mazda P5
hi all. just purchased my first mazda yesterday, a 2002 P5 with a ton of miles (187xxx) and a recently rebuilt engine. currently getting 3 codes:

P0103: MAF sensor high input signal
P0300: misfire
P0301: cylinder 1 misfire

other symptoms: car idles poorly (fluctuates and will dip real low well first started, shuddery. less noticeable after warming up); seems to lack some power when driving.

plugs, wires, MAF, cylinder 1 coil recently replaced (april). possibly O2 sensor? EGR? searched like a madman and most of the suggestions were the same (the things that've already been done). any guidance from you fine people will be appreciated. cheers!
 
When i had my random misfire i replaced all the plugs and both coils and my cleared codes. They've never come back. im pretty sure it was the coils which were the problem. Along with the MAF i cleaned mine with intake/carb cleaner and let it dry for an hour or so in the shop before reconnecting and starting it and my codes all went out. :)
 
checked everything over again tonight with a mechanic friend of mine. plugs looked ok (running rich), MAF was clean and connected properly, wires are new, and the coils look newer. my buddy thinks it could be a lemon MAF (it was replaced with a reman.), a voltage/electrical issue at the MAF, or (least likely) the ECU is bad.

may be worth doing the plugs, coils, and wires on my own just to make sure, but i have a feeling it's something more sinister. taking it to a shop on friday, but would like to avoid it if at all possible. any further suggestions? thanks all!
 
update - took it to a garage this morning and learned the following:

- there's no misfire while driving the car, computer only picks it up at idle (could be that it's not actually misfiring and that the funky idle is causing it to think there's a misfire in 1)
- idle is still really funky (nearly stalling, fluctuating)
- mechanic seems to think it's either the MAF sensor or a vacuum leak

any ideas on where to check for a vacuum leak? though i thought a vacuum leak would make the car run lean, not rich(?).

probably have to bite the bullet and try a new MAF sensor.
 
call around for a MAF sensor, and see if you can get any kind of return policy for it. (if it doesn't help) explain that you are trying to diagnose a problem. P0103 IS related to the MAF sensor. it is entirely possible that the MAF was not reconditioned correctly. a bad MAF would also cause a misfire.

failing that, it might be worth the $75 diagnostic fee from mazda to figure out the problem, so you're not just throwing parts at it.
 
I know this is a different vehicle, but I had the coils replaced on my honda van. A day later it was misfiring again. The mechanic said one of the coils was defective. Maybe it's applicable to your situation?
 
check your intake tube and make sure nothing is cracked especially between the accordion looking section
 
Pull the wires off the plugs, put some dielectric grease in the holes where it seats on the plug. Do the same with the coils.
 
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