need some help- rough idle problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cheatham · 12-16-2002, 10:51 AM

this is a new problem and mostly only during cold starts. after warming up and going to idle my truck is running very rough. also it sounds like the water pump is shot (that rattling sound). I would think this could also be the reason it is idling rough and finally dying. I dont have the problem after driving for 10 minutes. but when i took the belt off and turned the pump by hand it is smooth and quiet. could it be shot anyway and is it likely the problem (ignition and fuel have not been a problem and are set correctly)

thanks in advance
Jack

Tynee · 12-16-2002, 11:52 AM

I'm goin' out on a limb here, but check the alternator before you buy a water pump. Not gettin' enough juice would effect the idle, but I can't think of a reason that a water pump would effect the way the truck idled. The Alt could be that rattling sound you are getting.

Gordo · 12-16-2002, 09:21 PM

Just for the process of elimination, rub a bar of hand soap along each side of the v-belt and see if the noise temporarily goes away, if so you have a glazed belt and can make quite a racket, (usually happens from a few drops of anti-freeze spilled on it) clean pulleys and replace it. The rough idle could be many things, vaccum leak(s), readjust carb air/fuel settings, float settings, choke settings, faulty ignition wire(s), plugs to name a few and it doesn't hurt to double and triple check these items, you may see something that was missed before.

cheatham · 12-17-2002, 11:27 PM

Well, I ended up pulling the alt and the water pump as well as hoses, belts, tstat, etc. The water pump felt sort of tight and after reading your post tynee, I spun the alt. and it was the source of the noisy so i removed it too. After replacing everything I was quite surprised at how much better she runs.

Nothing like getting a strong spark, huh. Good call on the alternator.

It wasn't real cold this morning, but it is running much smoother already.

Peace
Jack

ChevLoRay · 12-18-2002, 10:37 PM

I had a '65 Chevy pickup that had problem with the water pump and that caused the truck to have a vibration....a SEVERE vibration! I had a vacuum guage on it and I knew it wasn't a dropped valve, because the vacuum was steady. I looked at the engine while it was idling, and saw that the fan/alternator belt had a twist in it and that caused the end of the shaft on the water pump to bend. That little fiasco cost me about $200, back in '77.....new water pump, new 4-row core for the radiator, etc.

All I did was rev up my engine to show the kid next to me that my truck sounded better than his Pontiac. Guess I was the sucker, huh?

12-16-2002, 10:51 AM	#1
cheatham I need a brake! Join Date: Jul 2002 Location: Nashville, TN Posts: 474	need some help- rough idle problem this is a new problem and mostly only during cold starts. after warming up and going to idle my truck is running very rough. also it sounds like the water pump is shot (that rattling sound). I would think this could also be the reason it is idling rough and finally dying. I dont have the problem after driving for 10 minutes. but when i took the belt off and turned the pump by hand it is smooth and quiet. could it be shot anyway and is it likely the problem (ignition and fuel have not been a problem and are set correctly) thanks in advance Jack

12-16-2002, 11:52 AM	#2
Tynee I miss this truck. Join Date: Dec 2001 Location: Lexington, KY U.S.A. Posts: 2,863	I'm goin' out on a limb here, but check the alternator before you buy a water pump. Not gettin' enough juice would effect the idle, but I can't think of a reason that a water pump would effect the way the truck idled. The Alt could be that rattling sound you are getting. __________________ '07 GMC Acadia SLT. Sweet ride. '08 Crew Cab Z-71 short bed. Really like this truck A LOT.

12-16-2002, 09:21 PM	#3
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	Just for the process of elimination, rub a bar of hand soap along each side of the v-belt and see if the noise temporarily goes away, if so you have a glazed belt and can make quite a racket, (usually happens from a few drops of anti-freeze spilled on it) clean pulleys and replace it. The rough idle could be many things, vaccum leak(s), readjust carb air/fuel settings, float settings, choke settings, faulty ignition wire(s), plugs to name a few and it doesn't hurt to double and triple check these items, you may see something that was missed before. __________________ 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.

12-18-2002, 10:37 PM	#5
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	I had a '65 Chevy pickup that had problem with the water pump and that caused the truck to have a vibration....a SEVERE vibration! I had a vacuum guage on it and I knew it wasn't a dropped valve, because the vacuum was steady. I looked at the engine while it was idling, and saw that the fan/alternator belt had a twist in it and that caused the end of the shaft on the water pump to bend. That little fiasco cost me about $200, back in '77.....new water pump, new 4-row core for the radiator, etc. All I did was rev up my engine to show the kid next to me that my truck sounded better than his Pontiac. Guess I was the sucker, huh? __________________ 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.

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12-17-2002, 11:27 PM	#4
cheatham I need a brake! Join Date: Jul 2002 Location: Nashville, TN Posts: 474	Well, I ended up pulling the alt and the water pump as well as hoses, belts, tstat, etc. The water pump felt sort of tight and after reading your post tynee, I spun the alt. and it was the source of the noisy so i removed it too. After replacing everything I was quite surprised at how much better she runs. Nothing like getting a strong spark, huh. Good call on the alternator. It wasn't real cold this morning, but it is running much smoother already. Peace Jack



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