03 silverado running rough

Thanks for the tip. I put 150 miles on it today and it seems to be running fine.

LIKE2BUILD wrote:

Thunderbolt wrote:
Update. I am not positive it is fixed, but it may be. I am ashamed to say the spark plugs must have had more miles than I thought. They were worn bad and instead of a .060 gap they were at .090+. I changed them and it runs great and idles smooth, but I am not positive the actual problem is fixed.The reason I say that is because the truck had cooled down and if I am not mistaken the coil packs can act up when hot. Is that a correct assumption ? It is idling smoother than it has in awhile.Any guesses on whether the problem is solved ?? I got the ac/delco plugs the dealer told me to, but the new ones are only .040 instead of .060. The dealer said they changed the specifications.

Yes, electrical gremlins like to show up in hot conditions. It's also possible you might have one or more coils that are marginal and with that excessive plug gap couldn't deliver enough juice to jump the gap and properly fire the cylinder(s).

Take a look at this GM coil testing guide to see if you ignition coils are good or failing.

KJ

Thunderbolt wrote:
Update. I am not positive it is fixed, but it may be. I am ashamed to say the spark plugs must have had more miles than I thought. They were worn bad and instead of a .060 gap they were at .090+. I changed them and it runs great and idles smooth, but I am not positive the actual problem is fixed.The reason I say that is because the truck had cooled down and if I am not mistaken the coil packs can act up when hot. Is that a correct assumption ? It is idling smoother than it has in awhile.Any guesses on whether the problem is solved ?? I got the ac/delco plugs the dealer told me to, but the new ones are only .040 instead of .060. The dealer said they changed the specifications.

Yes, electrical gremlins like to show up in hot conditions. It's also possible you might have one or more coils that are marginal and with that excessive plug gap couldn't deliver enough juice to jump the gap and properly fire the cylinder(s).

Take a look at this GM coil testing guide to see if you ignition coils are good or failing.

KJ

Thunderbolt wrote:
Update. I am not positive it is fixed, but it may be. I am ashamed to say the spark plugs must have had more miles than I thought. They were worn bad and instead of a .060 gap they were at .090+. I changed them and it runs great and idles smooth, but I am not positive the actual problem is fixed.The reason I say that is because the truck had cooled down and if I am not mistaken the coil packs can act up when hot. Is that a correct assumption ? It is idling smoother than it has in awhile.Any guesses on whether the problem is solved ?? I got the ac/delco plugs the dealer told me to, but the new ones are only .040 instead of .060. The dealer said they changed the specifications.

Yes, the coil packs will misbehave when hot (when they're failing). But you may have also fixed it by replacing the plugs. A few weeks ago my stepson's Rubicon had a P0302 code (#2 misfire) and after replacing the coil pack it was still there. New plugs fixed it....

Update. I am not positive it is fixed, but it may be. I am ashamed to say the spark plugs must have had more miles than I thought. They were worn bad and instead of a .060 gap they were at .090+. I changed them and it runs great and idles smooth, but I am not positive the actual problem is fixed.The reason I say that is because the truck had cooled down and if I am not mistaken the coil packs can act up when hot. Is that a correct assumption ? It is idling smoother than it has in awhile.Any guesses on whether the problem is solved ?? I got the ac/delco plugs the dealer told me to, but the new ones are only .040 instead of .060. The dealer said they changed the specifications.

Fuel filter.....

USAFBILL wrote:
Go to Auto Zone or one of the automotive stores that will read the codes for free. When ever one of my coils went out I went and had the codes read and they always showed which cylinder coil was bad.....Might get a replacement from the junk yard and save a little money

Second that. Most auto parts stores will read your code for free and then look it up and give you the possibilities. The light will not usually come on until the code has been repeated a few times, so there may be something there.

Go to Auto Zone or one of the automotive stores that will read the codes for free. When ever one of my coils went out I went and had the codes read and they always showed which cylinder coil was bad.....Might get a replacement from the junk yard and save a little money

Thunderbolt wrote:
I am thinking coil pack as well. Is there a way to test them ? I bought new plugs to start because it is over due for them. It is shuddering bad enough where I am not going to drive it until I figure it out. It was a crappy weekend. Not only did I not get a deer, the rectifier on my 4 wheeler shorted out and started smoking. I went and paid Yamaha 160.00 for a new one and now my truck.

That does suck. But that's the way it goes with mechanical things sometimes. My Chevy is a 5.3 and has plug wires (though short ones). I ASSume the 6.0 is similar or the same. Without a misfire code, you're going to have to check each cylinder for spark (again, I'd wait for a code). I stick a screwdriver in the end of the wire and set it close to something metallic. Spark should be clear and evident. If not, there's your problem cylinder. Word to the wise - do not hold the screwdriver while testing. Or have some unsuspecting helper hold it. A good time will be had by all.

I am thinking coil pack as well. Is there a way to test them ? I bought new plugs to start because it is over due for them. It is shuddering bad enough where I am not going to drive it until I figure it out. It was a crappy weekend. Not only did I not get a deer, the rectifier on my 4 wheeler shorted out and started smoking. I went and paid Yamaha 160.00 for a new one and now my truck.

Common problem is coil failure on one of the cylinders.