Misfiring on 3 cylinders

[MHW100]

Hi. I have a 2022 built Gen 2 that has about 5k on it in a 2017 350. There are intermittent misfires on 3 cylinders but not throwing any codes. The Ford tech is going to try plugs but are there any other known things that he should try?

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[klawrence]

Hi. I have a 2022 built Gen 2 that has about 5k on it in a 2017 350. There are intermittent misfires on 3 cylinders but not throwing any codes. The Ford tech is going to try plugs but are there any other known things that he should try?

could swap the coils , and see if the issue follows the coils or stays with the cylinder. Are they all on the same bank ? cam timing request and cam timing actual the same ?

 

[WItoTX]

Just to clarify, is the Ford tech the same guy/shop who built your motor?

 

[MHW100]

It was a long block warranty replacement at a different dealer. Not all on the same bank. I was thinking switching the coils around. I’ll mention about the cam timing thank you.

 

[JAJ]

Question: How do you know that there are misfires on three cylinders if there aren't any codes? Or did you mean that the only codes are the misfire codes, nothing regarding anything else?

In any case, have you tried switching to a different gas? I run Shell 93 rather than Chevron 94 because the car seems to run smoother with it. I'm not sure if it's available where you are, but fuel can cause misfires, so maybe just run a tank of Shell 91 if 93's not available.

 

[MHW100]

At idle after warm up the idle stumbles and recovers. Went for a drive and Ford tech was able to see the misfires on a graph on his laptop.

The purge valve was not functioning so that was replaced previously.

interesting. I’ve been running chevron 94. I can’t believe it would create misfires but worth trying if we hit a wall on the diagnosis.

 

[JAJ]

At idle after warm up the idle stumbles and recovers. Went for a drive and Ford tech was able to see the misfires on a graph on his laptop.

The purge valve was not functioning so that was replaced previously.

interesting. I’ve been running chevron 94. I can’t believe it would create misfires but worth trying if we hit a wall on the diagnosis.

I agree that Chevron 94 is unlikely to be causing misfires, but a change to a different fuel would confirm that it's not the cause. My theory is that there's not a lot of ways to cause a stumble at idle (and only at idle) without leaving a code in the ECU. It's either fuel or spark, and that's pretty much it. The fact that it moves from one cylinder to another suggests fuel, because spark would likely be localized to the same cylinder(s) each time.

Also, even if the fuel's good, any water (condensation) in the fuel tank from the car sitting for a long time could cause misfires if it gets sucked into the engine's fuel system. Ethanol-free Chevron 94 won't interact with water but ethanol blended fuel will gradually absorb it and get it out of there. Again, it's a long shot, but it's worth a try and there's no downside.

 

[klawrence]

Does it have an after market cold air intake ?

 

[MHW100]

I agree that Chevron 94 is unlikely to be causing misfires, but a change to a different fuel would confirm that it's not the cause. My theory is that there's not a lot of ways to cause a stumble at idle (and only at idle) without leaving a code in the ECU. It's either fuel or spark, and that's pretty much it. The fact that it moves from one cylinder to another suggests fuel, because spark would likely be localized to the same cylinder(s) each time.

Also, even if the fuel's good, any water (condensation) in the fuel tank from the car sitting for a long time could cause misfires if it gets sucked into the engine's fuel system. Ethanol-free Chevron 94 won't interact with water but ethanol blended fuel will gradually absorb it and get it out of there. Again, it's a long shot, but it's worth a try and there's no downside.

Thank you. I think it shows up in the same 3 cylinders. I’ll change the fuel if we start hitting a dead end.

 

[MHW100]

Does it have an after market cold air intake ?

No its stock and no tune.

 

[DCShelby]

Any rodents around that might have chewed into the wiring loom?

 

[MHW100]

Any rodents around that might have chewed into the wiring loom?

No thank goodness.

 

[MHW100]

Seems the plugs weren’t gapped properly or had changed overtime. All new plugs so peace of mind and hopefully the idle will be stable.

thank you for everyone’s help.

 

[MHW100]

back again guys unfortunately. Purge valve, plugs, changed. Tried different fuel. No codes. Doesn’t seem to be misfiring as much but occasionally at a stop, clutch in, engine warm the idle drops momentarily

Out there question but is there any way it could be the aluminum flywheel and McLeod doing something to cause it to stumble?

 

[JAJ]

back again guys unfortunately. Purge valve, plugs, changed. Tried different fuel. No codes. Doesn’t seem to be misfiring as much but occasionally at a stop, clutch in, engine warm the idle drops momentarily

Out there question but is there any way it could be the aluminum flywheel and McLeod doing something to cause it to stumble?

Has it had a crank relearn?

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