Misfiring cyl 4

[magikflight]

I have a motor that was missing on cylinder 4, same code you have. Burnt exhaust valve was the culprit.


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[Bronson9856]

how bad was that to get fixed? What did you have to pay for that?

 

[magikflight]

how bad was that to get fixed? What did you have to pay for that?

Tbh I’m not sure. I bought the car like this. I am replacing the whole motor. Compression was shit on the other cylinders. Gunna put a built motor in it. Car hasn’t been on the road in close to 3 years.


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[Easter Bunny]

There cx7 will work. It's pretty much the same as the gen 1 Mazdaspeed 3. You do need to be careful with them as most of them are not well maintained and oil coated valve train. It needs to be there turbo 2.3 not the NA 2.3

Cx 7 motor is lower compression. It will work but performance will suffer

 

[Ssinstaller]

Cx 7 motor is lower compression. It will work but performance will suffer

IIRC the CR was 9.5 just like the ms6/ms3, only the turbo was slightly smaller.

 

[Easter Bunny]

They run regular fuel though.

 

[Bronson9856]

Just to give an update, my mechanic is swamped at the moment. He says he has started it up a couple of times and he said that it seems like a blown head gasket. He is going to get to it in the next week or two. I fortunately have another vehicle to drive, so it hasnt been a hurry. I will keep the updates coming.

 

[Bronson9856]

Well, finally got an update. . My mechanic that was going to work on this got swamped and didn't want to take it on, just because he has other minor stuff that he can do and make more money. So it sat for about a year, since I have another vehicle to drive. So I took it to another shop that was recommended. They found the issue in the head, A BURNT VALVE! The head was taken off and reworked with 2 new valves, valves seals, etc. The Head put back on and the car runs like a champ! It cost about $2200, but at least I have a running vehicle. . and BTW, this completely solved my issue with it burning oil too. It was burning probably about a quart a week. Now, doesn't burn a drop! So everything is good on the homefront. . for now.

 

[Easter Bunny]

Doesn't seem to expensive for the amount of work either

 

[jsilva]

They run regular fuel though.

Although not directly thread related, I’m curious about this. What would be different that would cause lower compression? Couldn’t the fuel requirement be simply a tuning issue? (I’m genuinely asking, I have no actual opinion since I know nothing.)

 

[Easter Bunny]

I always thought the motors had lower compression and a smaller turbo

 

[jsilva]

I always thought the motors had lower compression and a smaller turbo

I have no reason to think you’re anything but correct. I’m just asking what about the essentially same engine would make it have lower compression?

 

[Easter Bunny]

I meant static compression as in compression ratio

Shorter pistons or rods