Misfire, only sometimes.

[Taylor513]

This has me scratching my head.. my truck skips / misfires only when it’s hot outside, like 100+ degrees. Well, living in AZ this is pretty common. It only does this when starting the truck, never while driving. Whenever it’s not hot the trucks starts like normal. My initial thought was spark plugs but talking with friends they said it could be a starter shim issue and isn’t that big of a deal. Was wondering if anyone had this same issue or any suggestions. 2015 with 99K on it. However it did it last summer as well but we had a mild summer so it didn’t do it that much.

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[DILLIGAF]

Check your stored codes
Check your plugs
Swap coil pack from a good Cyl
Ect ect ect !!! Its a process of elimination.

 

[Burla]

Misfire? Not sure about that, maybe just a hesitation? Did you get a p0300 code?

 

[Burla]

Have to replaced air filter? Hot air has less o2, it is possible it is an ai issue.

 

[Taylor513]

Misfire? Not sure about that, maybe just a hesitation? Did you get a p0300 code?

You’re right, not necessarily a misfire. It could be described as a hesitation. I haven’t received any thrown codes and the air filter is a k&n that I check and clean if needed when I change my oil.

 

[Taylor513]

Check your stored codes
Check your plugs
Swap coil pack from a good Cyl
Ect ect ect !!! Its a process of elimination.

No stored codes, I’ll have to go through the check list of things and see if any of them make a difference. Figured I’d try here first to save time if someone has had the issue before. Only happens when the truck sits in the sun and hits a certain temp outside.

 

[Taylor513]

I was told to not really worry about it since it’s not a everyday thing but only when the truck gets baked in the sun. However it bothers me when something is off like that with my truck and I’d rather it not continue to happen

 

[Burla]

next time it is hot, take of the kn and see if it does this.

You truck is always adjusting for o2 levels, all trucks do, sometimes when starting when hot it hasnt had a chance to adjust. Try opening the air flow on start, then if this is the issue, you can get a different filter.

 

[Taylor513]

Good idea, will do

 

[Taylor513]

So a little update.. taking off the K&N didn't see a difference. However when its hot out and I put the key to acc and then turn it off and repeat 3 times it starts just fine. I'm not a mechanic so I have no idea so I'm just speculating. Could it be a fuel pump issue?

 

[G-Ride990]

Any chance it happens more often when you are below a half tank of fuel?

Priming the pump 3x makes me think its more fuel pump related though.

 

[Taylor513]

Any chance it happens more often when you are below a half tank of fuel?

Priming the pump 3x makes me think its more fuel pump related though.

I'm also thinking its a fuel pump issue. I haven't noticed any difference when I have a full tank vs when I'm at a quarter or less. Which I thought was strange

 

[KoboldTaco]

I'm also thinking its a fuel pump issue. I haven't noticed any difference when I have a full tank vs when I'm at a quarter or less. Which I thought was strange

Or fuel pump relay. Had this exact issue in my old Pontiac.

 

[Taylor513]

Or fuel pump relay. Had this exact issue in my old Pontiac.

Good to know. Thanks for the heads up on that. I'll probably start at that and see if there is any changes