Miss/Flat spot just off idle

[beer30]

I just bought this 84 2.3L 4speed ranger and it's a great driving little truck if it wasn't for the miss just off idle. Truck runs fine at any other speed but that one spot, which at times is where it wants to cruise. I've changed plugs, wires, and the previous owner changed fuel filter, ignition box, and coil. I thought maybe the EGR was sticking because the miss gets better and worse just outa the blue at times. So I pulled the vac line going to it and the wires, no help. So even though the previous owner said the timing was right I decided to check it, was right but I retarded it and it run way worse so I advanced it and it seems to run better and atleast now the truck will cruise at 50mph+ ok but it still has the miss/flat spot and won't hold speed at 35mph. Not sure how far it's advanced cause the last couple times I bumped it I didn't bother checking. I do have a large hill by my house that I went up at 45mph and it didn't ping or miss so it seems to be happy with the timing where it is. Also now I can't get it to miss just free reving it and before it would so I want to lean towards a timing problem but I've watched it with a light and it advances smooth. It has the old style ignition box that isn't controlled by the computer but the carb is a feedback style. I was just searching and it seems all the computer does it adjust idle right? Or could the O2 sensor or something be screwing with it? This is the only problem this thing has and it's a fairly clean truck so I'd like to fix the miss and drive it. I'm out of ideas I can test without pulling it apart or throwing more parts at it which I hate to do. Anybody?

 

[martin]

Just off idle is always a touchy thing to get right with a carb. I would suggest richening up the idle mixture screws by half a turn. If you have emissions testing where you are you might have to readjust it to pass the test so remember where they were before you adjusted them.

 

[beer30]

I thought the computer controlled the idle mixture on this thing? I'll see if I can find a mixture screw tomorrow when it's light out.

 

[martin]

I'm not certain about the 2.3 but the 2.8 of the same vintage I believe has similar controls. the computer controls the high and low speed parts of the carb but only within certain limits and even then it leans out the mixture from a mechanical preset. as the carb wears air is able to enter through the butterfly shaft which leans out eh mixture.

 

[beer30]

No mixture screws that I can find, only idle speed. I just changed the cap and rotor as they looked nasty but of course it didn't change a thing. I'm really starting to lean towards that carb. Really thinking about putting an earlier carb without all the computer bs on it atleast then I can tune and not have the computer screwing things up.

 

[martin]

Look carefuly around the base of the carb for the mixture screws. They originally had metal caps over them so that you could not play with them. The cap would have to be removed of course.

 

[schmoo]

another thing to check is the accelerator
pump link. adjust it so there is no play.