Misfiring during cold start / idle and stuttering when revving at times

[brandon19]

Hey guys, been trying to figure out this misfiring for some time now.

Bit of history to understand where things are at to hopefully make this easier to understand. I originally had a built motor in my old MAZDA 3 MPS GEN1, all was running fine and no problems, but decided to switch to a MAZDA 6 MPS for a change, mainly for the AWD. In doing this, I removed the motor from my 3 and also added some changes, such as:
- 3" Catless Custom Downpipe
- G30-770
- CPE exhaust manifold with 44mm EWG
- 4" custom intake (unsure of brand or if it is even a branded one, bought from a wrecked car)

With the full swap done, for first start up I had to (obviously) update the MAF calibration, otherwise copied majority of the other maps from my 3 over to the 6, in which helped me get somewhere but no matter what I try, I just can't seem to get the car to run smoothly at idle and majority of the times when I rev around 1500-2500RPM, it stutters, although once RPMs are above 3000 or so it comes clean and runs no problem. I'm starting to believe that maybe the issue is else where, unrelated to the tune, but I can't see how hence the motor and sensors were just being ran in my old 3 that I pulled it from and really the major changes are what I had listed above.

I should also mention that I put the stock intake MAF housing on to disprove it being the 4" intake causing the misfires and that didn't change anything. I also has new spark plugs gapped to 0.26", pressure / smoke tested intake and boost pipes, confirmed no leaks.

I have attached a log and video to show what I mean, nothing stands out to me in the log so hopefully someone else picks up on something. The video is also recorded at the same time the log was taken.

Thanks.

 

[Crazycanadian]

Double check Non of your timing has slipped, on the washers. It sounds more like a timing issue popping out the exhaust then a typical spark or coil miss fire. Something might have slipped when you were swapping between cars. Also do you have the tune you can post?

The log isn't long enough to see how some things are going to settle out as it comes out of start up and warm up.. If you can do it without hurting the motor try getting a 3 - 4 min log, after 2 min of idling raise the rpm to 2k - 2500 and hold it for a little bit then let it idle for a little bit..

 

[brandon19]

I would be surprised if the timing has slipped, but I can agree it does sound like that. (Edit: I have just verified timing and it is all in check)

The new log is from cold, I let it warm up as much as I could without it going on forever constantly dying up and down. I had to blip the gas near the start because it was trying to die and then it fixed itself after that. I also included the holding 2500RPM at the end in the same log.

Tune:

 

[Crazycanadian]

To rule out tune issues I'd put all of your Spark, APP, VVT, and DBW maps back to stock..

 

[brandon19]

Unfortunately, still no difference. If anything, made it slightly worse.

Starting to believe there is a bad ground, or bad wiring somewhere on the car, hence that is the only thing different to the engine.

Edit: Once the car gets warm, it does seem to run substantially better. I have never had this problem before but maybe it is just one of those things I need to be mindful of for the future?

 

[Crazycanadian]

Unfortunately, still no difference. If anything, made it slightly worse.

Starting to believe there is a bad ground, or bad wiring somewhere on the car, hence that is the only thing different to the engine.

Edit: Once the car gets warm, it does seem to run substantially better. I have never had this problem before but maybe it is just one of those things I need to be mindful of for the future?

Try doing a cold leak down test. It's possible a valve isn't sealing and it gets better warmed up.. Or maybe an injector has gotten gummed up while sitting/during the swap...