motor misses at highway speed - The 1947 - Present Chevrolet & GMC Truck Message Board Network

crm318 · 01-24-2008, 05:29 AM

i notice that lately when i get on the highway for about 5 min or more, my motor starts to have a low drone and loss of power. i can tell that its not firing on all 8 at that point. i then pulled over at a gas staion to see if there is a burned wire arcing on the header which i has done before. everything was in check. i got back on the highway and it was good for another 5 min before it resumed missing. what could cause this? the i also heard a clicking coming from the pass. valve cover.

Huck · 01-24-2008, 06:53 AM

Plugs, Plug wires, vacuum advance issue~~~~. That's what I would look at.

ChevLoRay · 01-24-2008, 07:36 AM

It's called "Sometimin'...." Sometimes it runs okay, sometimes it don't...

From your description it's really hard to diagnose via internet. There's a lot of conjecture and supposin' to be done on our part, much of which won't do you one bit of good.

You should find a mechanic/friend and let him/her ride with you when you're sure it's gonna screw up.

crm318 · 01-24-2008, 08:26 AM

after reading an indepth article on how you should use manifold vacuum instead of ported on the advance, i put it on the manifold vacuum. could that be a reason?

Brad · 01-24-2008, 08:42 AM

I'm having the same problem-especially in 5th gear and going up slight hills...it's like it's running lean or something. I haven't had the desire to look into it since it's too cold outside.

Slammed70 · 01-24-2008, 10:56 AM

Look at your cap....cracks and carbon tracks in particular.

01-24-2008, 05:29 AM	#1
crm318 Alright Alright Alright Join Date: Mar 2004 Location: Midland, Texas Posts: 1,672	motor misses at highway speed i notice that lately when i get on the highway for about 5 min or more, my motor starts to have a low drone and loss of power. i can tell that its not firing on all 8 at that point. i then pulled over at a gas staion to see if there is a burned wire arcing on the header which i has done before. everything was in check. i got back on the highway and it was good for another 5 min before it resumed missing. what could cause this? the i also heard a clicking coming from the pass. valve cover. __________________ 1972 Cheyenne Chevrolet red and white 357ci, Vortec heads, GM Performance high rise intake, Comp 268H .454/.454 218/218 110 LSA Quadrajet carb, Flowtech headers, 2.25 40 series HEI, Curve kit, TH 350, 3.07 gears 275/60/15s on 15x8 rallies

01-24-2008, 06:53 AM	#2
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,261	Re: motor misses at highway speed Plugs, Plug wires, vacuum advance issue~~~~. That's what I would look at.

01-24-2008, 07:36 AM	#3
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Re: motor misses at highway speed It's called "Sometimin'...." Sometimes it runs okay, sometimes it don't... From your description it's really hard to diagnose via internet. There's a lot of conjecture and supposin' to be done on our part, much of which won't do you one bit of good. You should find a mechanic/friend and let him/her ride with you when you're sure it's gonna screw up. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

01-24-2008, 08:26 AM	#4
crm318 Alright Alright Alright Join Date: Mar 2004 Location: Midland, Texas Posts: 1,672	Re: motor misses at highway speed after reading an indepth article on how you should use manifold vacuum instead of ported on the advance, i put it on the manifold vacuum. could that be a reason? __________________ 1972 Cheyenne Chevrolet red and white 357ci, Vortec heads, GM Performance high rise intake, Comp 268H .454/.454 218/218 110 LSA Quadrajet carb, Flowtech headers, 2.25 40 series HEI, Curve kit, TH 350, 3.07 gears 275/60/15s on 15x8 rallies

01-24-2008, 08:42 AM	#5
Brad Out of the carpool lane. Join Date: Jan 2000 Location: Clark Co, WA Posts: 5,672	Re: motor misses at highway speed I'm having the same problem-especially in 5th gear and going up slight hills...it's like it's running lean or something. I haven't had the desire to look into it since it's too cold outside. __________________ 1968 C-10 SWB, 5.7 Vortec/700R4/3.73 posi, Torch Red 1968 Camaro, 250/Powerglide, all original (No, I'm not gonna drop a 350 in it!...Jeez!) 2000 Honda VFR in the faster yellow! 2008 Husqvarna TE-610 1967 C-10 SWB 'Six Appeal'-Gone but not forgotten...



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