1996 5.7 Vortec 'Hitching"?

Muskoka · May 28, 2003

I have a 1996 Yukon with the 5.7L Vortec that's got about 117000 miles on it.

At highway speeds under load, it seems to 'hitch'. It's almost a running out of gas kind of feel, but not quite as dramatic. It's not constant, and only hitches a few times over a couple hundred yards, then goes away for a couple of minutes and does it again. It feels like it's missing.

Where do I start? I have not checked anything yet and will likely look at the plugs first, but you may have other ideas.

Also at idle, it's got a bit of a tick. Nothing like the startup racket my '99 5.3 had, but a little tick. Any suggestions there?

americanmuscleman · May 28, 2003

I'd say start with changing the plugs and wires, and PCV valve. If that doesn't cure it, I'd take a look at your oxygen sensors and see what shape they're in. If the fuel filter hasn't been changed in a while, I'd change that as well.

Good luck

bigmack · May 28, 2003

Is this happening with the cruise on. I have the same feeling occasionally with the cruise on. It seems to hit the set speed then the cruise makes a quick throttle move back. Feels like what you describe. Again it is intermittent (maybe 2-3 times/ 100 miles on cruise control), usually unloaded on flat ground at the end of a minor rise where the truck has a little extra throttle but not much.

I just did new plugs, wires, cap, rotor, and fuel filter as part of a regular tune-up and this still occurs.

For me it's not a big problem, do you have fuel mileage issues etc to support the thoughts it might be a miss or otherwise?

k1500chevy97 · May 28, 2003

Shot in the dark but if all that fails my 97 4.3 was doing the same thing and it turned out that the catalytic converter was shot and not flowing right

badhammer · May 31, 2003

could also be the toqure convertor clutch going on and off. when it does this it feels like an engine miss.

Muskoka · May 31, 2003

Electrodes? We don't need no stinkin' electrodes!

I pulled the plugs, and came out with these:

Plugs

You don't think that may have had anything to do with my problem, do you?

Maybe the boot on #7 not being fully seated played a roll?

I've not had a chance to really get out on the highway to test run it, but the couple of 10-15 minute runs I have been able to drive have not resulted in a duplication, so perhaps a combination of the two was the root of my problem.

BTW, I've only had the truck for 2 1/2 weeks, so I take no responsibility for the condition of these plugs!

Muskoka · May 31, 2003

Is this happening with the cruise on. I have the same feeling occasionally with the cruise on.

It didn't seem to make a difference. It would happen with the cruise on and with it off, though the morning I started this thread (w/o cruise) it really chugged for a few seconds at about 65 under load & felt like I was running out of gas - not that that's ever happened before

It seemed it was actually a little less pronounced with the cruise on, but since I did the plugs, PCV etc, I haven't had it again....yet.

bigmack · June 6, 2003

Your plugs don't look to bad. The platinum eletrodes are still intact. The darker brown/black seems to be somewhat normal for thes plugs with lots of miles. How were the gaps ?

Did you replace with platinums or copper?

There's been alot of discussion here about the merits of copper vs. platinum. Myself I reinstalled platinums as the plugs are quite hard to get at with the headers. Ended up fabricating my own socket to get to 3 of them. For a stock engine the platinums will work just as well as the copper and you have the added bonus of not having to change plugs for 60,000 miles. May as well get your money's worth.

Glad you problem is solved.

Muskoka · June 7, 2003

The gaps were a little big - certainly bigger than .060, but not huge. My main concern with the old plugs was how little of the electrode was left in terms of their diameter - it was just a little stub.

I went with copper based on the hotter spark/cleaner burn argument. I have also since changes the spark plug wireset, and have noticed a real difference compared to what I started with.

The tough ones to change were teh back three on the passenger side, but pulling out the air intake box made them much easier to access.