High RPM misfire, dealer says it’s normal!?

[Zig]

the CEL only flashes for misfire when the amount of misfires exceed the allowed value

The code will be cylinder specific (P0301 to P0308 on a 8 cylinder engine telling the tech exactly what cylinder was not firing off correctly, or if there are multiple misfires it will be P0300 and then other P030X codes.

You can have misfires, usually sporadic that are not enough to trip the light and set a code, you find those by doing a dive into Mode 6 data, then cylinder contribution, and you will see misfire counts for every cylinder, and when you see one or two that far exceed the value the rest of the cylinders are showing those are the cylinders that are misfiring.

Now the question is if you were bouncing it off the rev limiter, and the computer was dropping fuel by not pulsing the injector or not firing the coil, would it show a flashing CEL indicating a misfire.

Or a top end air leak, what’s the ratio when you trip the light?

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[Skye]

Since around 1000 miles. Even if they were just put in I fail to see any possible correlation between drop in filters and a misfire.

While not specific to them, we've seen several posts pasts of weird things happening when K&N filters are used. I forget the brand name, but at a recent car meet, someone mentioned Serpent, Specter or something of the sort which had given them codes and faults in a previous generation of Mustang.

I realize it's happened sometime after-the-fact. FWIW, I think it's something worth considering.

Are the aftermarket filters in use oiled or dry?

 

[n_123]

While not specific to them, we've seen several posts pasts of weird things happening when K&N filters are used. I forget the brand name, but at a recent car meet, someone mentioned Serpent, Specter or something of the sort which had given them codes and faults in a previous generation of Mustang.

I realize it's happened sometime after-the-fact. FWIW, I think it's something worth considering.

Are the aftermarket filters in use oiled or dry?

They’re the steeda ones so oiled.

 

[n_123]

the CEL only flashes for misfire when the amount of misfires exceed the allowed value

The code will be cylinder specific (P0301 to P0308 on a 8 cylinder engine telling the tech exactly what cylinder was not firing off correctly, or if there are multiple misfires it will be P0300 and then other P030X codes.

You can have misfires, usually sporadic that are not enough to trip the light and set a code, you find those by doing a dive into Mode 6 data, then cylinder contribution, and you will see misfire counts for every cylinder, and when you see one or two that far exceed the value the rest of the cylinders are showing those are the cylinders that are misfiring.

Now the question is if you were bouncing it off the rev limiter, and the computer was dropping fuel by not pulsing the injector or not firing the coil, would it show a flashing CEL indicating a misfire.

It was a P0300 code.

 

[n_123]

It was a P0300 code.

Also no bouncing off the rev limiter, just up there in the RPM band.

 

[Skye]

They’re the steeda ones so oiled.

Could of fouled up the maf's

That was my thought. No filter maker in-particular, but I've noticed a few posts on this topic and the difficulty of getting the right amount of oil on the filter. Enough to be effective, without so much you run the risk of fouling the MAF/s.

I've not used an oiled filter before. IDK if it's a simple visual check, or something more involved. While doing that, the MAF connectors could be confirmed as seated well and secured.

I think @smurfslayer raised the issue in a previous thread on K&N and oiled filters. I later found several blog posts on the topic.

The K&N blogs were often quite defensive, K&N attempting to quell concerns over their products: that they were not defective, but people were installing them (too much oil) incorrectly.

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