Misfire under load with no CEL

Canada_CX7

Red Line
Hey guys, I'm having an ongoing issue with misfires that I'm trying to track down.

What happens:

Under load, particularly when going up a hill, the engine will misfire a lot at between 2700-3300 RPM. This gets particularly bad on cold and wet mornings and reduces when engine warms up. If I put the transmission in manual mode and drop it down a gear or two to bump up the rpm past this range it runs fine until the rpm drops down into this range again.

What I've done to fix this:

replaced MAF sensor, no change
replaced coil packs and plugs, no change

Any ideas what to try next? I would think fuel system, but wouldn't the fact that it runs smoothly if I can get the RPM past this range rule that out?
 

MoistMazdas

Banned
:
2015 Mazda 6
Hey guys, I'm having an ongoing issue with misfires that I'm trying to track down.

What happens:

Under load, particularly when going up a hill, the engine will misfire a lot at between 2700-3300 RPM. This gets particularly bad on cold and wet mornings and reduces when engine warms up. If I put the transmission in manual mode and drop it down a gear or two to bump up the rpm past this range it runs fine until the rpm drops down into this range again.

What I've done to fix this:

replaced MAF sensor, no change
replaced coil packs and plugs, no change

Any ideas what to try next? I would think fuel system, but wouldn't the fact that it runs smoothly if I can get the RPM past this range rule that out?

I had the exact same symptoms as you with a faulty ignition coil on my BMW 528i. very strange that the coil pack replacement did not fix your issue. even more strange still that you do not have a misfire code.

honestly, my only other guess would be fuel injector(s)
 

Canada_CX7

Red Line
Yeah the most annoying part is the no CEL.... actually I had thought to check the injectors, so maybe that's why I'll have a look at next. I forgot to mention in my previous post that I have tried running injector cleaner through the system a couple of times to no avail, but that doesn't necessarily discount the possibility of an injector issue.
 
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