97 Sierra engine miss while driving

[Masterb4tes]

So a few days ago I got my first American truck, a 1997 GMC Sierra 1500 extended cab. Now I have my first problem. Disclaimer, I'm not with the vehicle at the moment, my dad has it and is playing with it, he is good with pre EFI stuff but today was the first time he had heard the term OBDii.... so no codes yet. Engine had no issues yesterday, Bout 115000 miles on the clock

Truck starts fine, idles fine and can be revved fine in park/neutral. Put it into Drive, still idles fine but when driven you get an even regular misfire, CEL comes on solid, then flashes, and solid again. The engine isn't running rough exactly, just a regular miss, with a slight loss in power. Vehical can still be driven, no hesitation on throttle, makes speed ok.
What trips us up is that the problem only seems to occurs when the vehicle is in gear.
Otherwise, spark plugs, fuel filter, fuel pump and distributor cap/rotor are all things we plan on checking. OBDii scanner is on the cards but the truck is out bush at the moment, there isn't exactly a shop to go buy one. Thoughts?

Cheers
MB

 

[Erik the Awful]

Buy a good quality distributor cap and rotor, decent plugs and wires, and if you need to rely on this truck, carry a spare ignition module.

 

[Artinaudio]

I know this may sound weird but have you tried shifting the transmission manually? If all the fuel spark ect. Has been checked and all seems right then I'd look towards the transmission.

 

[Masterb4tes]

So the initial idea for this truck is indeed to be a reliable daily. With the scope to do a restore in future years.
We factored in basic maintenance items like filters and plugs from the beginning. Will source distributor and rotor in the meantime.

We will experiment with gearshift and reverse and see what it does. I'm just curious how the gearbox could affect ignition, other then providing load on the engine? If I understand correctly throttle position is relayed to the gearbox?

 

[Artinaudio]

It's never personally happened to me but a buddy of mine has, his truck would seem to have a miss under load, usually at highway type speeds. Turned out the trans wasnt down shifting fast enough causing a miss type effect. He fixed the trans issue & problem went away. The way I see it is like this, wont cost anything to try.

 

[Masterb4tes]

I have good news, it seems one of the ignition leads was secured poorly, resting on the extractors. Lead has been sorted and the problem is gone... so we will be getting all new leads. We will check through the rest of the ignition system as we go.
It seems there are no clips to hold the leads above the extractors, something to look for I guess

 

[Schurkey]

1. Most Americans probably don't know that "extractors" are "headers".
2. The plug wire retainers must have been removed. There's a thousand ways to route and secure plug wires...just make sure that the wires for #5 and #7 are kept well-separated, and where they have to cross, they should cross at a 90 degree angle. You DO NOT want the spark intended for #5 to inductively couple to the #7 plug wire.
3. Whatever your eventual solution to the scan tool may be...you WILL need one if you're going to be working on a computer-controlled vehicle. Trying to fix a computer-controlled vehicle without a scan tool is madness. I've bought all my scan tools "used" from eBay; but how willing folks would be to ship to Australia is another issue. I have done that, and filling out the Customs paperwork is a dreaded task.

 

[Masterb4tes]

1. Haha, I forgot about that. I'll do my best to speak 2 languages while here
2. Good tip in regards to #5 & #7, the vehicle will be off the road until I move back to North Queensland, so we have plenty of time to sort things like this out. I'm about 1600 miles away atm.
3. I'm looking into a few options. Any suggestions would be appreciated. I have a buddy near Gainesville Fl who is happy to send me stuff if need be. I was wondering if a Tech 2 clone will work? They were used on the early 2000 GM Holden Commodores which were LS powered.

 

[df2x4]

I was wondering if a Tech 2 clone will work? They were used on the early 2000 GM Holden Commodores which were LS powered.

Should be a good option if you're only worried about GM vehicles. The most recent software supports everything from 1991-2013.

 

[Masterb4tes]

Cheers, I think I can get a Tech 2 easily enough. Dad has a Rodeo (Isuzu/GM) so for the two vehicles we work on a Tech 2 should be OK, I don't touch the wife's Toyota, it's the reliable modern car.