Diagnosing Misfire

[Tnort]

I have a misfire that I am trying to figure out. It started as an intermittent mild stutter that only occurred in 5/6 gear at low RPMs and mid to high throttle input. At that time I could let off the gas for a moment or down shift and it would go away. Over the course of the last week it has rapidly turned into a misfire that happens in all gears, it feels less severe in 1/2, but will shake the entire car if I throttle up in 4/5/6 above 4k RPM. I just changed the plugs and ignition coils and there was no change. I changed back to the stock map from the cobb stage 1, and it improved slightly, but was definitely still there. The car seems to free rev just fine, and the misfire is worst under the highest engine load (accelerating in high gear low RPM).
I reset the codes right after I changed the plugs and coils and drove around for about an hour tonight and nothing popped up, the check engine light has not been lit through any of this. Any ideas for me? Thanks for any help on this.

 

[M0LTEN]

Maybe check the gap on the plugs. To much and it might be blowing out the spark.

 

[Tnort]

Is that something that could happen slowly over time?

 

[the duke]

What were the CEL codes?

Also, what grade of fuel did/are you running?

 

[Fiestig]

As mentioned previously, double check gap and adjust for your mods if necessary. It's the easiest first step to try if you don't have a CEL.

It can happen over time if you have iridium plugs. Just for reference, ruthenium plugs will not gap degrade.

 

[Tnort]

I always run 93. Can you gap iridium plugs? that's what I just installed. I don't remember the code numbers, but they were related to the evap system. There was also one for bank 1 afr.

 

[Sam4]

Check the gap - it's too wide. I put the Iridium plugs in a while back - they're at least .030. Also basics - how's the air filter? I need to clean and re-oil mine...

 

[Tnort]

Are there some parameters I can monitor on the AP to help me diagnose this? I will check the plug gap.

 

[Dialcaliper]

You can regap almost any single ground bar type plugs - it’s the multi-ground plugs that can’t be altered easily

Monitoring suggestions:
Air Fuel Ratio (Both actual and desired)
Boost Pressure
Ignition timing corrections
Load (desired and actual)
Fuel rail pressure
Short term and long term fuel trims
Misfire count per cylinder
Wastegate duty cycle

Since you have the Accessport, your best bet to actually take a data log and look over it later rather than trying to watch the gauges while driving

Someone put a list here of all the choices:

https://cobbtuning.atlassian.net/wiki/spaces/PRS/pages/96996998/Ford+Data+Monitor+Support

 

[XR650R]

Check the gap - it's too wide. I put the Iridium plugs in a while back - they're at least .030. Also basics - how's the air filter? I need to clean and re-oil mine...

This. ^ "Pre-gapped" is a joke. Manufacturers can't anticipate every possible use of a spark plug. My tuner told me to gap them at .025. I did, and all is well.

Makes me think of other jokes, like 10,000 mile oil change intervals or "lifetime" transmission fluid.

Sure, it will last until the warranty expires. That's the lifetime of a new car in the manufacturer's world.

 

[dhminer]

This. ^ "Pre-gapped" is a joke. Manufacturers can't anticipate every possible use of a spark plug. My tuner told me to gap them at .025. I did, and all is well.

Makes me think of other jokes, like 10,000 mile oil change intervals or "lifetime" transmission fluid.

Sure, it will last until the warranty expires. That's the lifetime of a new car in the manufacturer's world.

The lifetime trans fluid one kills me. No chance in hell

 

[XR650R]

The lifetime trans fluid one kills me. No chance in hell

I know, right? How long is the lifetime of the car? Until the tranny disintegrates from lack of service and it's not worth replacing, so you have to scrap it?
Far-sighted motherfuckers, I'll give them that!

 

[HAHAFiST]

Any resolution here? I’m going through the same thing.

 

[Tnort]

Well, it actually ended up being a busted CV joint that was only making noise under load. It didn't clunk under partial throttle or even turning, just medium to heavy acceleration. It was about time for new plugs any ways, so not a total loss, lol.