I have an 87 D-150,318,auto,that wont idle.I checked all the vacuum lines and they seem to be ok.Last night i removed the carburetor and took it apart and blew out everything that looked like it might have been dirty.it really didnt look that bad,put it back on the truck and I still have the same problem.The truck starts fine but it sounds like its misfiring when you hold it above idle but as soon as you let off the gas it goes dead.I replaced the distributor cap and rotor button about a week ago,before this problem started.Also, when driving it misfires at any rpm,not bad but you can feel it.Any help would be greatly appreciated.

 

HMMM, where to start?
Are you sure you got the plug wires back on correctly?
Hows the plugs and plug wires?
Have you tried adjusting the idle mixture (the 2 screws at the base)?
Is it idling too slow?
Checked the timing?

 

You made sure the timing is good?
It misfires above idle but do you have power to excelerate and drive at highway speed?
Did you spray around for vacuum leaks?

 

The problem started 2 days after the cap and rotor were changed,plugs are six months old and plug wires are ok.Not great but ok.I haven`t adjusted the air screws in quite awhile so I don`t see where that could be the cause.The truck ran fine on the way home from work monday night but tuesday morning it was missing.Nothing had been changed or adjusted.Can`t check the timing because I cant get it to idle.I also replaced the fuel filter.I believe I`ve eliminated fuel delivery but am open to any suggestions.I`m stuck driving my wife`s Grand Cherokee while my baby sits in the driveway.I feel like maybe it may have jumped a tooth on the timing gear but I can`t say what leads me to that conclusion.

 

Has anyone ever heard of a bad spark advance causing this problem?

 

If it started after a cap and rotor change,check on those,check for carbon tracking inside of cap,moisture,rotor defects,wires pushed tight in cap?

 

Yep,all good but listen to this-A friend of mine stopped by today with a friend of his. We were talking about my problem and he asked if he could hear it.I got in it to start it for him and it started right up,sounded great,IDLED, and has been running great ever since.This guy healed my truck without even touching it.( it`s a miracle). It must have been trash or something in the carburetor I was so sure I had clean.Not sure why but I keep expecting it to act up again,but so far it`s doing fine.Thanks for the help though. And you never did tell me who makes those seats you have in your truck.