Mechanic Suggested I Replace the Engine After Taking it in with P0304 Code.....

07-cx7

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Mazda, CX7
I have a 2007 Mazda CX7 with 144k on it. I have had more issues than I can count and have usually been able to fix them until this latest issue...

Car has been driving very poor for the past 2-3 months but haven't had a chance to spend time on it (figured it needed a tune up). Been getting two reads from the CEL, P0304 and P2177.

Worked this weekend on it (new coils and sparks). Expected the issues to stop and they did not.
Took it into the shop today and the mechanic said I would need a new engine and he does not recommend replacing it (due to age of car and miles).
He was getting a combustion reading of 80-85 out of cylinder 1 and 4... he put oil in there and was getting a reading of 120... This was his explanation of how it was an internal engine issue and there is not hope for my engine.... He said he could do a carbon clean out (as it is DI) but said he does not recommend as he does not think it would help.

As I was in shock over this, I decided to turn to this forum...

Any suggestions?
(shocked)(shocked)(shocked)(shocked)(shocked)
 
ouch, yes a dry compression test should be over ~160 and closer to 180psi wet...

Driving with a misfire for 2-3 months is never good...the 2.3L turbo motor replacement is about $4000-5000 after labor...
 
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Your mechanic started well, (plugs and coils), but then misdiagnosed (mine did the same). You do not need a new engine. it is unlikely that you have a cracked cylinder or valve problem: 99% sure it is your injector seals (and perhaps your injectors as well but probably not). A good mechanic will change that in ~5 hours. That said, by now you probably have a second problem, which is your catalytic converter is probably shot too.

Are you in Southern California by any chance?

Here is the thread I developed to document this issue when it happened to me last month (all fixed):
https://www.mazdas247.com/forum/showthread.php?123861548-P0303-and-failed-compression-test

If after changing your injector seals you still have a 2177, change your MAF (but I would bet you won't even have that issue after resolving your compression issue). That takes about 2 minutes even if blindfolded. You can get the Walker MAF on Amazon for ~$40 (works great on my '07 CX-7).

PS: a carbon clean will only make it worse... For me, this issue ironically happened 500 miles AFTER a carbon clean. You can remove all the carbon you want, if you are not reaching pressure, you can't have an ignition.
 
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