I have a cx-7 2007 2.3l turbo, I had a engine light come up P0303. The car started dropping revs in gear reverse worse then days latter shuttering. I replace coils an sparks cleared code an it re appeared. I changed manifold gasket an cleaned everything along the way checking vac lines also, come up empty handed the shutter went away a little now back. I currently have a engine light blinking at me 20 times, with now P0303 an pending P2178 any help please

 

Swap injectors around, clear the code & see if the misfire moves cylinders.

 

Cheers for the advice, I’ve ran some injector cleaner through it An topped up with 98 when it got to a quarter less the of fuel. An cleared all codes.. so far so good occasional shuttering with Ac on an in gear but no where as bad. I am swinging towards sticky injector or fuel issue would that cause these codes?

 

buy a quart of Marvel additive. Put 4.oz to 10 gallons in gas tank to clean fuel injectors and the rest in with your new oil change. This will gently clean the sludge and carbon deposits inside the engine, Next time you change your oil all the gunk will go out. This is a VVT engine with a Turbo that gets really hot spinning up to 200k rpm. Clean oil is essential and new filter every 3000 miles to keep this engine running well.

 

THe car only has 120k on it would the rings burn out this soon? There is no smoke or fuel smell coming from the tailpipes would this be the case if oil was burning or fouling that cylinder. Plugs 1,2,4 are rich white colour An then plug 3 is fouling out black

 

with code 2178 probably not oil but a bad fuel injector fouling the plug. too much fuel is bad for the engine, causes the metal to get too hot and also the catalytic converter. If you replaced the coil and it still is 303 I would consider pulling the fuel injectors and having them inspected and cleaned. While your in there you can replace your PCV valve that is a bear to get to. Where I live fuel injectors are cleaned and rebuilt for $25 each at the NAPA store. Getting to them requires taking the intake manifold off and the fuel rail. not easy to do. Here is a link to the CX7 shop manual where you can study procedures for diagnosing trouble codes. https://www.mazdabg.com/ftp-uploads/...zda%20CX-7.pdf

 

No worries cheers. I should have replace PCV when I did manifold gasket, I’ve been sus about injector 3 Mabey sticking open at times, all other codes have cleared an the only re-occurring fault is P303 cyl 3 mis fire, I’m about to pull my hair out an Torch the b***h

 

Is there any info on engine vac line diagram, Mabey I’ve missed a crack deeper then the manifold, once The intercooler comes off (on top of engine) you can’t start the car to help find it

 

The car is now booked in to get injector checked in cyl 3. I have a hunch it’s letting to much fuel in like you said above, I’m doing an oil change an have a strong fuel odour as if it’s leaking down the cyl 3 wall unburnt due to misfire, thanks for all the advice guys fingers crossed it’s just a grommet or washer.. will keep you posted on the fix

 

James,
What ever came about with your cx7 as I am having the same problem.