Misfire under load.

Brenneman2385 · Apr 17, 2019

TobyU said:
Short of vacuum leaks, the only thing I know that will cause those types of conditions is the air bypass valve sticking. Maybe you could take it off and clean it out well with carb cleaner and work it back and forth or pick up a use cheaper for junkyard or a cheap one off of eBay.
I guess it's possible for a flat spot or a low fuel signal from the throttle position sensor but I doubt it. You should be able to monitor live data on a scan tool and maybe see more.

TobyU, thanks for the response. I am not familiar with the air bypass valve you are speaking of. Can you tell me where this is located, or provide a picture? I googled it but it kept coming back with IAC, which this does not have.

Thank you,

TobyU · Apr 17, 2019

Brenneman2385 said:
TobyU, thanks for the response. I am not familiar with the air bypass valve you are speaking of. Can you tell me where this is located, or provide a picture? I googled it but it kept coming back with IAC, which this does not have.

Thank you,

Sorry, air bypass valve and IAC are interchangeable. On a phone so wasn't able to scroll up through all the threads to see start year were talking about.

comobreadman · Apr 28, 2019

hey just a thought - make sure all your connectors that are on the coils are good . I have had to replace 2 of them over this year due to misfires that at first I thought were coil failures. Sometimes after throwing code it would fix itself and be good for a while and the code would go away on its own. I had one that was shorting out and caused the truck to almost not want to run and the other one I just replaced after thinking a coil was bad but realized the coil made no difference connected or not .. Just saying . I don't know why connectors go bad but they do . I did only have this problem on this truck that I bought with 120k on it . All my other vehicles with coils I always worked on and never had this problem but I owned from close to new.

Brenneman2385 · May 1, 2019

Hello all,

Thanks again for everyone’s help. I wanted to advise that I purchased the xct4 from 5star tuning and tried a tune with changing the idle in gear up to 650, and I am not having any issues as all now. This thing shifts and runs better than it has since I purchased it. I am not sure what the root was, likely just the wear on the engine and pure coincidence that it happened when it did, but it’s running like a champ now.

Again thanks for everyone’s input!

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Misfire under load.

Brenneman2385

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