Random cylinder misfires

backyarder1 · May 2, 2016

I have a 2004 GMC Sierra 1500 that has pretty much just been sitting in my driveway for over 2 years. It belonged to my husband and he passed away. Anyway, I've probably only driven it 4 or 5 times since he died and now I'm trying to decide whether to get it fixed or not. The battery has died several times and I have charged it and replaced it. Now it has a check engine light on that WAS blinking yesterday but now is steady.

My question is, do you think that just the fact that it has pretty old gas in it could cause the random cylinder misfire. I have added newer gas whenever I drive it but, like I said, that isn't very often.

Any thoughts?

dkjbama · May 2, 2016

I'm very sorry for your loss.

I'd start with the simple things. Top up with a tank of fresh 93 octane fuel. Ethanol free if possible. If it's going to sit, treat the fuel with sta-bil. I use the Sta-Bil Marine 360 formulation, 1 oz per 10 gallons of fuel. Today's fuels, especially with ethanol, degrade pretty quick.

If that doesn't fix it, my next step would be a tune-up: plugs and wires, maybe coils.

Regarding the battery: these trucks will drain a battery in as little as a month. If it's going to sit, either get a battery tender to leave hooked up or disconnect the battery if the truck will sit idle for any length of time.

backyarder1 · May 2, 2016

Thanks. I was originally going to take it to a mechanic today but when I looked up all the things it could be, I don't think I want to spend that much money on it. Plus, since the check engine light was blinking yesterday, I wasn't sure I should even drive it to the mechanic.

muddkatt · May 2, 2016

2 year old fuel could be the issue for sure. I would not drive it with a blinking check engine light. Like dkjbama stated, adding some fresh 93 octane will help freshen up the gas. I hate to say it, but you might want to sell the truck since it only gets driven a couple of times a year. I know it can have sentimental value to you is why I didn't really want to mention it.

backyarder1 · May 2, 2016

The check engine light isn't blinking now, although its still on. I just replaced the battery yesterday and drove it around a little yesterday and today and the check engine light quit blinking. I will probably see if I can see any sparks from the spark plug wires tonight after it gets dark and see if that could be it. I don't think the spark plug wires have ever been changed.

Yes, I definitely need to sell it. Kind of nice still seeing his truck out there in the driveway but he would be giving me grief for keeping it. LOL.

txab · May 2, 2016

Get your codes read to see what you're dealing with, have them cleared and see if they return. Driving it bit more regularly with fresh fuel may clear up some issues. Old ethanol fuel isn't a good thing. It of course could be leaky intake gaskets

backyarder1 · May 2, 2016

The guys at the car parts place read the codes yesterday when I swapped out the battery. P0300 - Random cylinder misfires within a predetermined period of time.

dkjbama · May 2, 2016

How many miles on the truck. If over 100k, then how long since the last tune-up?

backyarder1 · May 3, 2016

Over 100K. Not sure it ever had a real tune-up bad had the sparkplugs replaced in 2012.

dkjbama · May 3, 2016

These days, a tune-up basically consists of plugs and wires. Given that the plugs have been done and it's a random misfire instead of a specific cylinder I'm even more inclined to think it's a bad fuel issue.

If possible, I'd siphon the old gas out and start with fresh, but I don't know if you can get a tube down the filler to siphon it out. I know you can't on my 08.

backyarder1 · May 3, 2016

I meant to run it last night and see if I could see any sparks from the spark plug wires but it was raining. I'll try to do that tonight. I did see an old "suggestion" from a tire store that said "fuel induction" which I assume was something they were recommending but they were probably just going from mileage. Would it help, at this point, to put something like sta-bil in it?