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'04 GMC Sierra Wet Weather Chuggin'

Hello everyone, hopefully somebody can shine a little light on this issue I’ve been having:

So I have a 2004 GMC Sierra 1500 RWD named Beulah and she is quite the beast… She’s got over 260,000 miles (given to me by my father after he used it as a work truck, so mostly highway mileage) and a few little kinks and issues. The one at hand today is some lugging/chugging of the engine usually after wet weather. I live near Lake Michigan and we just got dumped on by lake effect snow, but over this weekend it warmed up and we got quite a bit of rain. After this rain, I went to drive my truck and while it starts just fine and idles just fine, for about 10 or so minutes of initial driving, while at speeds anywhere from 0-30 miles an hour or so, Beulah seems to run a little rough. It almost sounds like she’s lugging a bit or something’s sticking in her engine. After about 10 minutes or so of driving it seems to fade away so my guess is its just some moisture getting into something and eventually evaporating from the heat of the engine. My questions are 1. Is this bad for my truck? 2. Is there a way to prevent this without spending a fortune? and 3. Any guess on how much longer this truck will last?

Much appreciated everyone,


My 2002 Kia sedona does the same exact thing…

What engine? How old are the ignition wires? When were the spark plugs last changed? Wet weather misfires are most often secondary (high voltage side) ignition problems.

Have the plug wires been replaced? I would start there. It’s usually the problem.

Thank you for your suggestions everyone. I’d have to agree that it is something electrical, as Beulah has always seemed to have had electrical issues - from lights in the radio/AC panel not turning on, to AC resistor issues, to overall wiring. As long as I have had it, which is now going on about 3 years, to my knowledge now wiring whatsoever has been replaced. My dad and I have both said for years that the truck needs a tune up including changing the plugs and the wiring altogether. We have simply never had the time (and I don’t have the money) to do so.

MY 2 CENTS: To be honest, I’m not sure exactly what engine model it is other than it is all stock and pretty much the baby in the line of Sierras in terms of power. We have never needed to pull much of anything until now as the family has recently gotten a 22 foot camper - dogs the heck outta ol’ Beulah. In regard to wet weather misfires, should I maybe look into protecting the existing wiring from the wet weather somehow? Is there anything in place already that should be checked that is supposed to be protecting wiring like this from wet weather?

knfenimore: I do not believe these wires have been replaced, but it would definitely be a good start.

Again, thank you all for your comments.

Actually, Ignition wires and plug wires are one and the same. There is nothing you can do to protect them. They just deteriorate with age, that’s normal. They are extremely easy to change and are not expensive. You just pull one end off the spark plug and the other end off the distributor cap (or coil pack) depending on which you have, then push the new ones on.