2014 Mazda CX-5 misfire

[duker733]

I have a 2014 Mazda CX-5 with the 2.5L engine, (187,000km) and it has an audible misfire, but only on warmup from being cold. As soon as it warms up it runs fine.
It has thrown the PO301 misfire on cylinder 1 code.
I have changed the plugs, and even swapped cylinder 1 & 2 coil packs and it still throws the misfire code for cylinder 1 after clearing it.
Pretty sure if it was ignition related it would have a misfire on more than just warmup.
It has a new MAF sensor, air filter, and I just removed and cleaned the carboned up throttle body and MAP sensor in the intake.
Any other ideas on what it could be? Is it possible it could be the fuel injector on cylinder 1? Or carbon buildup on the valves?
Not sure what else it could be.
Thanks for any insight on this

 

[N7turbo]

Can you define at what part of "warmup" does it run normally? Can you drive it and actually feel the misfire before it smooths out?

Otherwise it sounds like you did your diligence on the spark side. I think you're right that it's time to look at the fuel injectors.

 

[ADS-B]

I just replaced the spark plugs today. I would've replaced the ignition coils, too, but the auto shop did not have them available. If spark plugs replacement did not fix your issue, I would definitely consider to replace the ignition coils.

 

[N7turbo]

I just replaced the spark plugs today. I would've replaced the ignition coils, too, but the auto shop did not have them available. If spark plugs replacement did not fix your issue, I would definitely consider to replace the ignition coils.

He did move the coil packs and the misfire remained on #1.

 

[ADS-B]

Then I would look at the injector.

 

[Jmaz]

As suggested above, look at the injector(s). If you haven't already, I'd start with a can/bottle of injector cleaner in the gas tank. Chevron Techron ( not the weaker Techroline if it's still around) Injector cleaner or Berryman B-12 Chemtool which I consider a strong cleaner. Also one of the BG products.

 

[duker733]

thanks for the suggestions, but from most of the research I've been doing it looks like it's leading to carbon buildup on the intake valves. Especially because it only has a misfire when starting from cold. It runs dead smooth once it warms up. Anyone done a mechanical cleaning on the intake valves? I've seen quite a few videos of this being done, and it looks like a dirty, but pretty straightforward job. I can't believe how much carbon buildup there is on these GDI engines

 

[cz5gt]

walnut blasting. Look for shops around you who can do it and yea it is messy.
The other option is expensive but disassembly of the valves and you can do 1870,000 km more unless something else fails.

You should see what the Diesel DI look after 100k miles but they dont have a throttle body and air is less important there so no misfiring.

 

[Kedis82ZE8]

If valve cleaning doesn’t help maybe look through these but many you have already covered

https://static.nhtsa.gov/odi/tsbs/2017/MC-10129368-9999.pdf

https://static.nhtsa.gov/odi/tsbs/2016/SB-10092582-6903.pdf

https://static.nhtsa.gov/odi/tsbs/2016/SB-10085446-6903.pdf

 

[duker733]

If valve cleaning doesn’t help maybe look through these but many you have already covered

https://static.nhtsa.gov/odi/tsbs/2017/MC-10129368-9999.pdf

https://static.nhtsa.gov/odi/tsbs/2016/SB-10092582-6903.pdf

https://static.nhtsa.gov/odi/tsbs/2016/SB-10085446-6903.pdf

wow thanks for all that great info

 

[edmaz]

If it were mine I would do compression and leak down tests. If carbon is holding an intake valve on #1 even slightly open, it will become apparent from that testing. And those tests will also either eliminate or confirm any other mechanical issue with the engine as well.

 

[madar]

As suggested above, look at the injector(s). If you haven't already, I'd start with a can/bottle of injector cleaner in the gas tank. Chevron Techron ( not the weaker Techroline if it's still around) Injector cleaner or Berryman B-12 Chemtool which I consider a strong cleaner. Also one of the BG products.

This first. I've gotten rid of quite a few misfire codes with a good cleaner, especially if you aren't using top tier gas. Easiest thing you could do. Techron is great stuff, so is Berryman B-12.

 

[duker733]

yes I will for sure be using a good fuel additive as well. Looking at redline total fuel system cleaner

 

[duker733]

Well, I tackled the big job of cleaning the intake valves today. Boy they sure were nasty 188,000km's
Car runs like an absolute dream now. No more missing and stuttering on cold starts. Seems to have a little more throttle response now too. Guess time will tell how much better the fuel mileage will get. Not a hard job at all, just time consuming and lots of scrubbing. Just presoaked the valves with carb cleaner and used the zip tie method in my drill and some nylon brushes that fit in my drill as well. The key is to soak them real good and then the hard carbon turns to goo. I just cut up a whole bunch of small rags that i jammed in down to the bottom with a screwdriver to soak all the carbon up and it worked pretty well. Took me about 6.5 hours from start to finish. I see why walnut blasting would be the preferred quicker and easier method though. If I had to do this more than once in awhile I would get one.

 

[sm1ke]

Nice job with the cleaning!