Mazda 6 Forums banner

P0300

9K views 41 replies 6 participants last post by  SIX_SEVEN_ONE 
#1 ·
Hey M6ers,

Getting this code on my 03 V6 manual.
Starts up and idles fine.
When driving however it feel real sluggish and weak.

Been doing some searching around here and it seems like either coil packs or a vac leak but before I order them I wanna be sure.

When at idle I sprayed starter fluid around the manifold and vac lines but no luck.

Pulled the plugs that I just installed last week and 3 are dark/black, 2 are light brown and 1 like yellowish/white.

Any info would be sweet. Thanks in advance. :)
 
#2 ·
I went ahead and order a set of coil packs. 90 bucks per pack if I was to get em locally.

Gave that a "No Thanks" and placed an order for all 6 for 80 bux.


One thing i will check when I get home is plug gap. I just trusted the manufacturer to pregap it correctly before shipping. ???
 
#9 · (Edited)
Update: Plug gap was definatly off. Gapped them to .044, put everything back together, test drove it with same issues.

Starts up fine, idles good, lack of power down low and bogges a bit when accelerating.

It does smoke out a bit out the back. If coil packs dont fix the prob I may look into changing out valve seals.

How can I confirm if the seals are out? Besides the smoke coming out the back what else can I do to confirm it is seals and not something else?

Thanks!!!!!!
 
#11 ·
Will do if the new coil packs dont fix anything.
I did do something like a compression test.
The kit I borrow didnt have the right fitting for the M6 so I used the rubber fitting end.
The one you just squeeze and seal against the plug threading.
Got about 155-160 on each cylinder.

Thanks flipper
 
#14 ·
Ya I got one on the way. Should be here today or tomorrow along with the coil packs.

Was working on my daily car yesterday and needed something from Napa.
The daily was on jack stands so i had to use the M6. It's all the same. When taking off from a dead stop you have to clutch ride it or it'll die. Almost like driving a car with a 4 puck unsprung clutch in it.

When reversing outta Napa it died because I didnt rev it high enough. After that it had a hard time starting up. I had to keep cranking it and sorta clear it out.
Maybe the plugs are fouled up???


Anyways I'll have more updates as soon as I install the new packs.

Thanks!!!!!
 
#17 ·
Ya mine gots this weird fitting on the rail, or near it anyways.
Cant find a tester to match this fitting locally so I'm just gonna tap into to it with fitting and mate it with my gauge I got lying around.

Friend of mine believes its the maf but could it be and not throw any maf codes.

Thanks!!
 
#20 ·
Ok so I removed the little valve fitting in the shrader valve and connected a hose to it.
On the other end of the hose I put a fuel gauge. Started it up and at idle its reading 65-70psi.
I know this is a bit high but will this cause the issues I'm experiencing???

Also on cold start it starts up fine and idles fine, then after driving a bit idle starts bouncing around and after I turn it off its hard to start back up.

Will inspect all the vac lines again.
As for the cats and pre cats, whats the precat? the one right off the manifold?
I found one cat under the cab and one under the motor(well I thing its a cat anyways).
Wheres the pre cats and how can I test/check them??

Ideas??? Thanks!!!!
 
#21 ·
theres 4 cats 2 coming right out of the motor and the one under the motor like you said and in this picture theres one at the very end after the 2 flex pipes. the one out at the end is what blew my first motor. i checked them while changing my motor. so how i checked them was to take them off my car. i uderstand that you can do a backpressure test or something. i dont know much about that. the one that as clogged for me i just rammed a pipe through it and put it back on. hope this helps!
 

Attachments

#24 ·
factory spec on fuel pressure

Fuel line pressure
L3: 375-450 kPa {3.9-4.5 kgf/cm2 , 55--65 psi} (I4)
AJ: 430-510 kPa {4.4-5.2 kgf/cm2, 63-73 psi} (v6)

I wouldn't be at all concerned about the cats just yet. They will cause a missfire due to damaged piston rings and shit in your intake track. Your compression test suggest that hasn't happened.

PS maybe I'm forgetting, but what brand plugs are you running at .044(which is a little low I might add)?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top