The dreaded "Misfire".....

Murraycroexp

Veteran Expediter
Before I spent money for a diagnosis, I thought I'd consult the professionals.....You guys.
I have a non-critical and occasional running problem I wanted to see if anyone had experienced.
2006 Express 2500 4.8L w/ 340K...
Cold starts great. Drives fine for hundreds if miles. I stop for fuel, or any reason, for 5-10 minutes. Restarts fine but has a DEAD MISS for about 1-3 minutes after restart. The miss kills about 75% of the power under acceleration. After the 1-3 minute period of the dead miss it immediately clears. And not gradually. It's like you had cylinders "turned off" and just flipped a switch to turn them back on.
I replaced the canister purge valve (by fuel tank) as it was pulling a huge vacuum leak when scanned for codes. I had heard this valve was notorious for getting stuck open with dirt. My idle has recently begun to degrade occasionally, from very slight to horrible at times.

Any clues? I hate to shut it down as my favorite, and trusted, shop seems to take 2+ days for anything.
 

paullud

Veteran Expediter
I'm wondering if it is a worn ignition coil absorbing heat when you stop which later cools down from air flow once you get moving.

Sent from my SCH-I535 using EO Forums mobile app
 

Murraycroexp

Veteran Expediter
I like that theory most. I think it "clears" too quick to be a vapor lock. Thanks!!!

Any other opinions? I won't be doing anything with it until this weekend at the earliest.
 

billg27

Veteran Expediter
Owner/Operator
Does it do this every time? I have the same engine and if I start it and notice a rough idle, I shut the engine down and restart it. Sometimes computers don't properly reset on startup. I've had this with cars also.

Or, with the 4.8 each cylinder has its own coil pack. Possibly one or more going bad. They can be tested, get a shop manual or get specs and test procedure from your trusted mechanic.

I have the same issue with my trusted mechanic at home. Needs a couple days to get me in. I wait until I know I'm headed close to home or when I decide to be home and call ahead and schedule an appointment day. They have always been able to schedule me in with a couple of days advance notice. The few times that I just showed up with an issue, they have made time for me. Great shop that I use!
 

Murraycroexp

Veteran Expediter
Pretty much every single time as long as I allow it to operating temp and it sits at least a minute or two.
 
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