I can't figure this out.... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

iluvmy72 · 10-18-2002, 03:10 PM

I picked up my truck from the tranny shop today.....like before it went into the shop it runs rough when it's in gear but when it's at idle, it runs perfectly normal.....someone told me that this is a sign that the engine is dying and I'm colse to needing a rebuild....is this true?.....it's really bad when I'm slowing down to a light and then I stop and then it starts to shake....but if I put it in park, it runs like nothing happend.....any help or info would be apreciated.

71GMC_3/4T · 10-18-2002, 03:40 PM

Could be several things, or a combination.
Timing. Vacuum advance, or mechanical advance, or sloppy distributor.
Worn out timing chain.
Vacuum leak, intake to head, or carb.
Leaky carb at throttle shaft.
Bad spark plugs or wires.
Bad points or dist cap.
I'm sure there are ohter possibilities...
I'd start with a full tune-up and see what you find while you're doing it.

Blazer1970 · 10-18-2002, 05:51 PM

Or the idle is just set too low.

**COBALT** · 10-18-2002, 05:57 PM

What do you mean by "runs rough"?

iluvmy72 · 10-18-2002, 06:46 PM

it almost feels as if the timing is off but I know it's not the timing.....because it runs so smooth at idle....but does this change when it's in gear?....also...I just had the rear main seale replaced....do I need to adjust something after this has been done?

my new 72 · 10-18-2002, 08:03 PM

I am haveing the same problem on my Fresh 383. I think I have it narrowed down to a vac leak, but I don't know where. I got the dist. from my brothers truck we tore down a few weeks ago, and it did the same thing. I tried changing the spring and weights, since it seemed to be a timing thing at first, but that isn't it. Now I have to find the vac leak. It's bu!!sh!t about this meaning it needs a rebuild. When I find out for sure about mine I'll let you know. If you find out about yours first shoot me a line.

Gordo · 10-18-2002, 09:04 PM

Give us some history on this engine/truck, we need more info like is it stock, modified and what has been done to the engine recently?

iluvmy72 · 10-18-2002, 10:39 PM

it's a 350 and everything is stock except for the Carter carb and K&N air filter.....I might be on to something though...the exaust manifolds are completely shot and there are a few exaust leaks now......also about a year ago before it sat for a year.....the water pump went out and the engine overheated to the point that it shut itself down and then when I lifted the hood, steam was coming out around the edges of the intake.....so I'm wondering if this too had something to do with it....but that's the history of bad in the last 6 years I've had it......Oh yeah....I burned out about 3 gallons of desile fuel 5 years ago......didn't do any harm though....just alot of smoke.....I'll tell ya guys.....I'm closer and closer to putting in that rebuilt Olds 350 longblock....but I' don't know what I need in terms of mounts for engine and pumps and alternator.

Paul Clark · 10-19-2002, 12:20 AM

Timing and idle were set with the truck in gear, right (hope I remember that correctly)
Check the intake and carb bolts (nuts)

Solver · 10-19-2002, 01:55 AM

If the truck has power brakes then with the vehicle running pull the hose loose from the power brake booster. If engine doesn't kill then your booster is leaking vacuum. I know this sounds weird but the vacuum as explained to me is also engine vacuum reservoir. Been through that before.

10-18-2002, 03:10 PM	#1
iluvmy72 Registered User Join Date: Jan 2002 Location: Springville, UT, USA Posts: 1,010	I can't figure this out.... I picked up my truck from the tranny shop today.....like before it went into the shop it runs rough when it's in gear but when it's at idle, it runs perfectly normal.....someone told me that this is a sign that the engine is dying and I'm colse to needing a rebuild....is this true?.....it's really bad when I'm slowing down to a light and then I stop and then it starts to shake....but if I put it in park, it runs like nothing happend.....any help or info would be apreciated.

10-18-2002, 03:40 PM	#2
71GMC_3/4T Weapons Of Construction Join Date: Apr 2000 Location: Colorado, USA Posts: 1,095	Could be several things, or a combination. Timing. Vacuum advance, or mechanical advance, or sloppy distributor. Worn out timing chain. Vacuum leak, intake to head, or carb. Leaky carb at throttle shaft. Bad spark plugs or wires. Bad points or dist cap. I'm sure there are ohter possibilities... I'd start with a full tune-up and see what you find while you're doing it. __________________ 1971 GMC 2500, 402/TH400 4.10 Daily Driver Lafayette, CO

10-18-2002, 05:51 PM	#3
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,510	Or the idle is just set too low. __________________ Tim

10-18-2002, 05:57 PM	#4
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	What do you mean by "runs rough"? __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

10-18-2002, 08:03 PM	#6
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	I am haveing the same problem on my Fresh 383. I think I have it narrowed down to a vac leak, but I don't know where. I got the dist. from my brothers truck we tore down a few weeks ago, and it did the same thing. I tried changing the spring and weights, since it seemed to be a timing thing at first, but that isn't it. Now I have to find the vac leak. It's bu!!sh!t about this meaning it needs a rebuild. When I find out for sure about mine I'll let you know. If you find out about yours first shoot me a line. __________________ I'm going to Law School, wanna debate? It's good practice.

10-18-2002, 06:46 PM	#5
iluvmy72 Registered User Join Date: Jan 2002 Location: Springville, UT, USA Posts: 1,010	it almost feels as if the timing is off but I know it's not the timing.....because it runs so smooth at idle....but does this change when it's in gear?....also...I just had the rear main seale replaced....do I need to adjust something after this has been done?

10-18-2002, 09:04 PM	#7
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	Give us some history on this engine/truck, we need more info like is it stock, modified and what has been done to the engine recently? __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

10-18-2002, 10:39 PM	#8
iluvmy72 Registered User Join Date: Jan 2002 Location: Springville, UT, USA Posts: 1,010	it's a 350 and everything is stock except for the Carter carb and K&N air filter.....I might be on to something though...the exaust manifolds are completely shot and there are a few exaust leaks now......also about a year ago before it sat for a year.....the water pump went out and the engine overheated to the point that it shut itself down and then when I lifted the hood, steam was coming out around the edges of the intake.....so I'm wondering if this too had something to do with it....but that's the history of bad in the last 6 years I've had it......Oh yeah....I burned out about 3 gallons of desile fuel 5 years ago......didn't do any harm though....just alot of smoke.....I'll tell ya guys.....I'm closer and closer to putting in that rebuilt Olds 350 longblock....but I' don't know what I need in terms of mounts for engine and pumps and alternator. Last edited by iluvmy72; 10-18-2002 at 10:42 PM.

10-19-2002, 12:20 AM	#9
Paul Clark Registered User Join Date: Apr 2002 Location: Center Point, IA Posts: 502	Timing and idle were set with the truck in gear, right (hope I remember that correctly) Check the intake and carb bolts (nuts)

10-19-2002, 01:55 AM	#10
Solver Registered User Join Date: May 2000 Location: Storm Lake, Ia Posts: 1,449	If the truck has power brakes then with the vehicle running pull the hose loose from the power brake booster. If engine doesn't kill then your booster is leaking vacuum. I know this sounds weird but the vacuum as explained to me is also engine vacuum reservoir. Been through that before. __________________ 1972 Cheyenne Super 20 LWB-Blue 1972 Cheyenne Super 10 LWB-Black 1972 Cheyenne Super 10 LWB-Red 1972 Cheyenne Super 10 LWB-green 1972 GMC 4x4 LWB-White 1971 Cheyenne 10 LWB-Ochre 1971 Cheyenne 20 Longhorn-Copper 1971 Cheyenne 20 Longhorn-Black 1969 Custom 10 LWB-lt blue 1968 GMC 3/4 ton-green 1968 1/2 ton swb stepside-silver 1967 Chevrolet CST 10 LWB-green 1967 Chevrolet custom 20 LWB-Maroon



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.