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.
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
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
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
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!
the valve covers, start it up at idle, the rockers should be popping, quick
you see some just going up and down, lazy like, the lobes are shot!
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
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.
You wrote on Thu, 11 Jan 2007 21:52:53 GMT:
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