My goodness, I think the Cow Chick might just be on to something, here...

I'm also betting that at idle, you'll see a slight rise and fall of the tach needle, not the dead steady rpm's that you should have.

 

+1 on the wiring, not so sure about the spark plugs but worth a check
could even be a sensor going out that the computer hasn't picked up on yet.

 

does it get rough when it starts surging?

 

Wow, I guess I am learning stuff and I got a brain to go with the semi-good looks... dang it I was suppose to keep that out of here... oh well...

Another example I remembered was a vid I put up a while back, it was from frostbite2009 when I went with the boys

http://www.youtube.com/watch?v=SvwjHY1Bw3Y

Listen to the last 2 secs of it, guess what he found was wrong with the Jeep a few days later... Yup, you guessed...

PS. - i didnt intend for that vid to become embedded... grrrrrr....

--Cow-Chick--

 

maby take your SC tune off back to stock then re program worth a 10 min shot

 

If it was the wiring or plugs, wouldn't it do the surging all the time, not just at 65+mph as Pyro described? To me, a problem with plugs or wires would manifest iteslf at all speeds, not just at highway cruising speeds.

 

That would depend on how badly off the problems are, best way to decribe the wiring is the line could be frayed or pulled, like a stereo speaker, it only does it sometimes and works when you put them in a certian position.

The spark plugs, thats really the same case, it varys on the power, how the driver drives, etc. When my twins 05 'balt went, she had the issue from 45-75MPH but not when it was 40 and below...

If you dont buy that, Pyro is well... pyro, and weird so you expected his truck to be normal?

--Cow-Chick--

 

he was on the interstate, cruising. I'd bet if he were driving around town, it would manifest itself at different times. He was also traveling a good distance, heat would cause an iffy boot, wire end or plug to fail during sustained driving at high temps...

 

So I guess the real question is, has it happened any other times other than when he was cruising down the highway like he described in the original post?

 

Well, well, well, the Cow Chick got it right. Just for the record, I knew the solution before posting the problem, it took Hammer all of 4 seconds to figure it out. The problem hadn't occurred around town because I haven't done much in town driving, mostly highway. It's a bad wire, running to the #5 cylinder plug.