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08-19-2002, 11:43 PM | #1 |
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Join Date: Jan 2002
Location: Beaver County, PA
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Help with rough running I-6
My I-6 started running a little rough 2 weeks ago. It would occasionally hesitate/miss (under load) - not always though. It idled like normal though. Last week it started doing it all the time even during idle. It has almost no power and even idles roughly now. At times you can hear a slight exhaust backfire also. I checked the compression: 1-143, 2-150, 3-130, 4-145, 5-149, 6-146. Although these numbers are not great they are about the same as when I checked it last year and it ran fine.
Possibly jumped a timing gear tooth? But then again it was intermittent at first and a timing gear would be sudden. I put an hei in last year and relatively new cap, rotor, and wires. Any ideas?
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67 LWB GMC 250 inline w/4spd manual Disc/power brake conversion |
08-19-2002, 11:54 PM | #2 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Check your fuel and air filters, douche it with some gum-out, and if still spittin and farting, try messing with the carb screws. Sounds like a sick carb to me.
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08-20-2002, 08:54 AM | #3 |
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Location: Arlington, VA
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This could be coming from the Department of Redundancy Department but, is timing and dwell (if you have points/condenser distributer) at specification? OOps, I just reread your post, you don't have points.
I mention this because last year I was experiencing the same symptoms. I was thinking "Oh no! Valve job time." The engine has a lot of miles on it. When I checked the timing to see where it was, I found out that the distributer had worked its way to being 15 degrees off!!! I was amazed that it ran at all. Reset timing and it runs fine. |
08-20-2002, 09:08 AM | #4 |
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Location: Beaver County, PA
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Thanx for the input guys. I will clean the K&N and replace the fuel filter tonight. I did the filter a few thousand miles ago but maybe I over oiled. I'll let you know.
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67 LWB GMC 250 inline w/4spd manual Disc/power brake conversion |
08-20-2002, 05:28 PM | #5 |
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Join Date: Jan 2001
Location: Killingworth, CT. USA
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Double check your tune-up parts and check for vaccum leaks. Don't worry about the timing gears jumping, this is a gear drivin cam, not a chain, if it sheared teeth off the stock fiber cam gear, it wouldn't run at all.
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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. |
08-20-2002, 09:54 PM | #6 |
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Join Date: Dec 1999
Location: TN/VA
Posts: 6,388
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replace your intake and exaust manifoid gasket both of them the one that goes on the block also the one were the intake and exaust manifoid bolts together and the doughnut to.
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08-20-2002, 11:27 PM | #7 |
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Location: Beaver County, PA
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Well no luck on the air filter or the fuel filter - changed both with the same results. I did find a bolt loose - one of the ones that bolts the intake/exhaust together. I'm now thinking that maybe the gasket seal was broken. I did tighten it and it still runs the same. Maybe my tomorrow project should be to put new manifold gaskets on.
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67 LWB GMC 250 inline w/4spd manual Disc/power brake conversion |
08-21-2002, 10:08 AM | #8 |
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Join Date: Mar 2002
Location: Floodwood Minnesota
Posts: 1,057
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free parts 4u
I recently acquired a parts truck with an inline 6. Inside the glovebox were some tune-up parts for it. There yours if you PM me your mailing address. I have no use for them. If you need other hard parts i have them as well. bruce minn
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1967 K30 Napco 292/SM420 original paint 30k miles 1968 K60 Napco 396/5spd. dbl frame 52" michelins 1969 K10 SWB GMC 454/4spd 6" 35's posi,hooks 1972 C30 longhorn,BB/AT,A/C,Tilt,Toolbox,lokr 1987 K20 Chevrolet Suburban. 6" lift. 5.7L/TH400 1979 K60 GMC Coleman 4x4, 427/Allison. |
08-21-2002, 12:39 PM | #9 |
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Location: Victoria, BC, Canada
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I'm betting something is amiss in the distributor area, have a look inside the cap for any busted or burned contacts, check the plugs for fouling, check the wires etc. The symptoms you described are very similar to what I went thru with my 350, I found the center contact in the cap was broken. Must have been a real light show inside, lol.
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1970 GMC 1500 Custom Original 350/TH350 Victoria, BC, Canada You can wish in one hand and crap in the other. See which one gets filled first. |
08-21-2002, 02:00 PM | #10 |
Progress = 0%
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Location: Kansas City, MO
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Loose or cracked vacuum hoses? Distributor advance froze up? My brother had similar symptoms (lack of power) and he found that his mechanical advance was froze up.
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Jason - '67 GMC swb | '57 Bel-Air 4dr hardtop | '56 210 4dr Wagon | 2000 GMC Sierra |
08-21-2002, 08:50 PM | #11 |
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Location: Beaver County, PA
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I've got it narrowed down pretty good now. It was not the manifold gaskets either. I still kinda thought it was an electrical problem so I thought of putting my timing light on the wire for each cylinder - guess what I found... Cylinders 2 and 3 are only firing maybe 1/3 of what they are supposed to be. I guess I found my miss.
Cap and rotor still look good. I'll try putting some new plugs in 1st and if that doesn't do it I guess it's cap and rotor time. Amazing being I changed all of those at the same time - maybe 2,000 miles ago. Gotta love those cheap parts. Anyway - Thanx alot for all the previous replies. They really helped me...
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67 LWB GMC 250 inline w/4spd manual Disc/power brake conversion |
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