heres the problem:
when at low RPMs, it misfires and bucks. when i sorta get on the gas its ok. when i get to about 45 it starts to buck again. i changed spark plug wires, and it still does it.

what led up to this:
i went out of town friday. i drive about 300 miles, most of the time going about 75-85. friday night and saturday it ran great. when i got to the first traffic light by my house coming home, it started.

i thought it might be bad gas, but i changed tanks and it was the same. im wondering if my headers screwed up my spark plugs, or if maybe i need a new coil. any insight?

 

when you changed fuel tanks did you also change your filter and pump. If not atleast change the filter, change the spark plugs also. Start with the cheap stuff. I highly doubt that headers are going to mess up your spark plugs.

 

What he is talking about when changing tanks, that truck has 2 fuel tanks, so he changed to the one he wasnt picking up from.

I had the same problem one time with my 87 silverado. I changed the plugs thinking that might be the problem. Ended up i missed the plug wire that was about half burnt through. Check yours out, when you added the headers, you might have missed a wire and its laying right up on it and burnt it just enough to cause that problem.

Let us know what you find.

 

my engine has been done for a few months. i havnt changed anything around. i went out of town, and when i came back it was messing up. something i noticed today--the truck runs good for the first 2 or 3 minutes, but once the engine warms up, it starts to misfire again. im burning a lot of fuel, and it sounds horrible. im thinking my sparkplugs are bad. im going to put my heat gun on the headers to see if i have a dead cylinder.

 

I would just replace the plugs anyways. If you have a spark strengh tester I would check each plug wire with that to see if there is a weak or broken wire. If they are all weak then it's the coil or wiring.

 

check your timing. Does it sputter at a certain RPM?Vaccuum Advance?

 

my timing has been good since i set it when i re-did my engine. could it have changed over the weekend just by driving? i dont know the RPMs, i dont have a tach since its an 87. im working on getting one though.i changed the wires on the passanger side because i had blow by and oil got on them and the screwed up. but i havnt changed the driver side since they were new (about 3 months ago). im going to change the plugs in the morning if it quits raining.

 

Check the distributor retainer or mark the distributor and something close to it and try to turn the cap. It is possible for it to loosen, though not common. Does you distributor have a vaccuum advance? Maybe there is a block or leak in the line.

 

It still could be your fuel filter, if you are saying that it runs for the first 2-3 minutes fine and then starts running bad it could be that your filter has a bunch of sediment in it and when it sits the dirt settles to the bottom of the filter then once the gas gets flowing it pushes all thatdirt near the filter outlet thus restricting it. Just a thought

 

Do you have Catalytic Converters? I've only seen it once, but, when heated the crap from years of "filtering" can turn into goo restricting the flow.
It wasn't fun using a hacksaw to cut exhaust on the side of a busy interstate.