77 chevy truck missing when warm

My 77 K10 developed a problem in the last few weeks, It runs great when it is cold, but when it gets warm and under a load,( like climbing hills), it starts to miss and sputter. I have changed the plugs, wires, coil and cap and
rotor, but nothing seems to help. Any one got any ideas of what i can try next?
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You don't give much information, such as engine type, temperature where you are at etc. If you live where it's gotten colder I would venture to guess that the choke isn't fully opening when the motor warms up and doesn't need it. Also air filter could be filthy and partially blocked. Could be a lot of other things as well, but that's a place to start.
Brian
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I think you have a partialy plugged fuel filter in the carburetor. it is inside of the carburetor where the fuel line comes in. they have a small filter and a sprong that allows the fuel to get in for a short time and then the spring return seats and it will miss from fuel starvation. i cleaned mine on the side of a mountain after it would hardly pull the hill. old john

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Have to agree with Brian. I wanted to add some information for your investigation. Take out your spark plugs and inspect them. They will tell you the story. 1. If they are black with soot that indicates too much fuel (choke not coming off all the way, etc.) or poor spark (check wires, cap, and rotor, which you've already done). 2. If the porcelain is baked white-orange or blistered and normal deposits are strangely absent, then your engine is running way too lean (look for a vacuum leak that is more prominent when the car is warm and the choke is off). After you fix your problem, pull out a plug and inspect it. It will have light tan-orange deposits on it (orange stuff is from unleaded fuel), if your truck burns a little oil (no big deal) there will be puffy charcoal grey deposits mixed in with the tan-orange along the outer curve of the ground electrode and other "cool " areas of the plug. Learn what this "good running" plug looks like (and smells like). If you don't know what it should look like when it's right, how are you going to tell when it's wrong? Have someone follow behind you when the truck is running rough. Floor it, and have them tell you if it belched out a cloud of black exhaust or not. Black cloud indicates too much fuel or extremely poor spark and will eliminate looking for any lean condition problems. I'm giving you the benefit of the doubt on the wires, cap, rotor, and plugs. That is the most logical place to start. I can't count how many customers have torn apart perfectly good carburetors (until they got their hands on them) when they actually had an ignition problem. Don't use the cheapest wires. Use NGK V-power plugs, old chevys burn oil, and the V-power plug provides excellent performance and has the highest resistance to oil fouling. If you weren't driving a Chevy with HEI ignition I would recommend checking the ignition coil too. An ignition coil's internal resistance rises as it gets warm and I have seen them cause a problem like this,... but not in HEI ignition systems. HEI systems have the coil protected in the cap (which you know because you've removed and replaced it, and the carbon rotor contact underneath it, when you replaced your cap). In the extremely rare cases when I have seen HEI coils fail, were mostly because they were accidently dropped when they were out of the cap. There's some basic stuff to go on. Can't emphasize developing plug reading skills enough. In 25 years I have found that quite often even the world's most expensive scope can be fooled,...but plugs never lie. Good Luck.
Old Wrench
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If it has a 4 barrel carb, take the top off and check the float while there is gas in it. I had a 77, and it had a BLACK bakelite, or whatever float...and that float didn't float, it absorbed the gas and let the engine flood, replace it with a brass one , and you might have a sweet running truck! While you are at it rebuild the carb, very easy, if i can do it anybody can! You might have a bad camshaft...lots a bad ones back then! pull off the valve covers, start it up at idle, the rockers should be popping, quick and fast!,if you see some just going up and down, lazy like, the lobes are shot!
Andy

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well if you sputter and miss while using gas pedal HARD, IT COULD BE THAT THE FUEL FILTER INSIDE THE CARBURETOR WHERE THE GAS LINE CONNECTS IS PARTIALLY PLUGGED. thet are made with a coil spring between the little filter and the carburetor that will push the filter back when pressure builds up and let more gas bypass the filter. the truck will then smooth out and as soon as the coil goes back to original shape, the plugged filter will cause the gas flow to diminish and the truck will sputter and mis for lack of fuel. it feels like the truck is out af gas(it is momentarily) and is easy to take out and clean. i had to do this on a logging road that was steep and fuel was starved, causing miss and sputter. i threw the filter away and no trouble since. i recommend you put an external filter on. old john
Hello, Andy! You wrote on Thu, 11 Jan 2007 21:52:53 GMT:
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Have you cnecked for Vac. leaks
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check you EGR...plugg it off and see the out come..I had a 79' chevy same thing that you are talkin about..plugged it off and man it came alive after that..
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