[majinkun180]

So I had another post about my car misfiring on the #2 cylinder and I swapped it out with a new ignition coil and it's been well over a month that it's been running fine but this morning I started to feel that shuddering of my car all over again. I scanned my car and of course the P0302 code is back but my cel is not on yet. I don't understand, could it be that the ignition coil I purchased from autozone is already dead or could it be something else.

I also read on the forums about cleaning the maf sensor but what else should I be trying? Please help, the shuddering is a lot worst than it was before for some reason. Thanks!

 

[BigAlDJ]

What kind of mileage is on your car?
Have you used fuel injector cleaner every 1/2 year?
is it shuddering all the time or under load @ higher rpm's?
When I had a mis-fire, they changed plug & coil. then they changed the fuel injector.
Good place to start.

Missfires can be caused by a million and one things,

Vac leaks
wiring issues
spark plugs(even fresh spark plugs that are crappy quality.... E3 and such)
alternators(search EMI)
MAFS
injectors
injector o-rings
intake gaskets
TB gaskets
PCV hoses
PCVs
malfuctioning EGRs
Malfuctioning CAS
o2 sensors
aftermarket intakes
intake hoses
vac lines
Timing chains
timing chain tensioner
Broken cam gears
Malfuctioning cam sensors
Incorrect Crank gears(the I4 has like 40 different configurations for whatever reason)
incorrect PCM flash
issues within the PCM
PCM wiring
bad diaphram within the FPR
issues within the fuel pump
dirty fuel filter
dirty fuel lines
PRE-CATS

On my 2006 Mazda 6 V6 3.0 ltr, they also changed the fuel tank and fuel pump (did nothing).
After they changed the left front pre-cat assembly problem was solved.

 

[majinkun180]

I have 102000k miles on my car. Changed all the spark plugs around 95k (kinda late I know). Maybe from 4-5 months ago I had the problem of the engine sounding weird as in almost stalling at a stop. When I'm at a stop the engine shudders and it struggles to accelerate. So back in January I got an odb scanner and found the code p0302 and someone suggested changing out the #2 ignition coil. As hard as it was to get to the ignition coil I changed it out and it's been running like new for the past 2 months until this morning. It's showing that the #2 is misfiring again.

Unfortunately I haven't been using an fuel injector cleaner at all. I hope that helps.

 

[BigAlDJ]

PRAY !
That's a lot of mileage.
I'd also check for a vaccuum leak. My brake vaccuum booster leaked causing bad idling at a stop, almost stalling (not common). PCV valve definitely change and inspect for cracked hoses. PCV hoses have cracked. The accordian intake hose between your throttle body and air filter have shown weakness in age and cracks to let in unecessary air not caught by mass air flow sensor causing roughness (Duct tape is a temporary fix as per RED GREEN).

 

[flipper66]

broken PCV throw a P300 code

Cracked accordian throws a P300 code

take off the plenum and check your intake runner gaskets. could be worn out.

remove the coil+plug and see what condition the plug is in. Being that it spent time when you had a bad coil, the plug likely got carb build up and may very well be running under compacity causing your issues.

move coil 2 to the front bank and see if the coil issues follow the coil.

This should help you rule out a douzen things.

btw, since when is 102k "A lot" of miles?

PS what kind of plugs did you put in?

 

[tkemme]

btw, since when is 102k "A lot" of miles?

I'm dating my self here, but a 100,000 miles used to be the end of a car's life. I've never owned a car past 130,000 until this past year. Not sure if it was a marketing thing to get people to buy new cars or just the fact that in Michigan a car is usually a rust bucket by the time it reaches that kind of mileage. The first car I bought in high school was a VW Rabbit for like $200. It was 5 years old and you could sit in the drivers seat and put your feet on the ground like Fred Flintstone. I welded in all new floors, drove it for 2 years and ended up selling it for $400. It was a blast.

 

[flipper66]

100k used to be the life of a car....... electronic fuel pumps was a novelty at one point too.

modern cars outside of rust problems not so much(less it is a lambo). O yeah or a rotary.... lol jk even those have the potential to last a lot longer than 100k with proper upkeep.

 

[flipper66]

btw al....... it was a smart ass comment when I made that list for you........ but I find it mildly amusing that you now chose to use it.

 

[BigAlDJ]

btw al....... it was a smart ass comment when I made that list for you........ but I find it mildly amusing that you now chose to use it.

Is it not true? Does it need to be modified?
What are hundreds of other people that viewed that list on the previous thread on Misfire Cylinder 1 believing.
I really hope the list is valid.

 

[flipper66]

No it is all valid.

Just ironic.

 

[majinkun180]

Thanks for the advice guys. I used NGk iridium spark plugs. I will be swapping out the coils from the #2 bank to another and see if it follows it. I have a few new spark plugs so I'll be swapping that out too. Thx will update tomorrow night!

 

[flipper66]

I had nothing but missfire issues with the NGK irdiums. did you re-gap them? the standard gap they come in is a .057 and our cars are speced for .052

My car ran like crap after running them.

 

[e4w]

got to be careful when gapping irridium plugs. ill still with the double plats!

 

[flipper66]

you are supposed to use a special tool to gap irdium plugs to not damage the tip.

thats why I stick to copper plugs.......

you couldn't pay me to use platinum

 

[mtcassell2]

Actually P0302 is cylinder #4 not cylinder #2. The codes run in firing order: 142536. You're fixing the wrong cylinder, that's why the code's coming back.

 

[tkemme]

My manual says he is on the correct cylinder?

 

[flipper66]

Actually P0302 is cylinder #4 not cylinder #2. The codes run in firing order: 142536. You're fixing the wrong cylinder, that's why the code's coming back.

1 2 3 <----rear bank

4 5 6 <----front bank

is the order of cyclindar #ing.

they firing order and numbering a different. 142536 is the order they fire.

rear bank, front, rear,front, rear, front as the crank cycles.

 

[majinkun180]

Okay so here is the update.

Checked the spark plug on #2 and of course flipper your right the spark plug was pretty much disintegrated. I've never seen a plug like this in my life. I should've checked the plug when I swapped out the ignition coil.

I didn't know it wasn't gapped to the correct space, I thought it came pre gapped to the correct amount, I got misinformed. So what do you recommend- brands? makes? for spark plugs.

The CEL went away for now and the car sounds alot better but who knows. I'll going to be updating again. Oh yeah i'll be posting the pic of the destroyed spark plug later since I took a photo of it. Thanks for all the help.

 

[BigAlDJ]

That spark plug didn't last long!
The coil really beat the crap out of it.
I have been using Denso Iridium Plugs for 2 years with no issues. Soon I will be putting some real coils on.
Denso # 5325 and/or 1T16#4 or IT16#4 (can't tell from my invoice)

 

[flipper66]

I only use NGK Copper plugs. we run V-powers in our daily drivers

the 6
the wife's G
brother's mach1
GMC1500
pacifica

We NGK copper race plugs in our race cars and drift cars and show cars.... They may not last as long as a Platinium or iridium, but I can trust them with sub 10 second cars better than anything else so thats good enough for me. I change them ~ every 40k and my car runs like a champ.