Hello, and I have a 83 F100, 4.9l inline 6cyl, 3 on the tree. All stock. The problem is when driving it will bog or have no pick up. But when sitting still or in neutral, you can rev it up and it seems to run great, but when you are driving it seems like it does not have the power going up hills. any ideas would be great.

 

Did this problem just start or did you do any work on the truck before this?

 

I have had the carb rebuilt, but had the problem before. And I have swapped out with another carb, and the samething. It idles great, starts very easy, revs good, only when you drive it, the problem is there. It is strange.

 

Right, a little more info would be helpful. When did this problem begin, and what was changed before that?

Pictures of your distributor and carb would help, too.

Your problem could be a choke not opening up, a distributor not advancing the ignition timing, or....

 

I did check the choke, and I even wired it full open, no different. I have not checked the advance. I have pulled the vacuum line off of it, and it does make a difference in the timing, the way it should. Timing is set at 10btc.

 

Is the catalytic convertor plugged?

 

I have not checked but I can feel the exhaust coming out the tail pipe. But if it was clogged, it seems like it would not idle or rev up correct.

 

Sometimes a catalytic convertor will be partially plugged and the back pressure build up will be more pronounced the faster, farther and harder one drives.

The same thing can be said regarding the fuel filter. A partially plugged filter can let enough fuel get to the carburetor for idling and racing the motor, but once one drives and "loads" the engine, the carburetor will be starved for gasoline.

 

I have changed the fuel filters twice. So I don't think that is it.

 

Well, it has to be either a fuel delivery issue, a timing/spark issue, or a plugged up exhaust. If compression is good and timing is set right, then you could still have an issue with the rest of the spark delivery system. Its possible your fuel is getting choked out. Pull the mechanical fuel pump and see if the diaphragm has a hole in it. Your going to have to start eliminating certain possibilities.

 

At this point in time, I am thinking exhaust. I will get back you with what I find. Thanks for all the assistance to everyone.
And I have found me another 1984 F150 XLT. I cound not resist the price.

 

Lets see some pics of that new to you pickum up truck

 

Not likely the answer, but you might want to look closely at the rubber fuel line sections between the fuel tank and the fuel pump. Old ones do get weak and collapse or have pin holes that allow air to be sucked into the fuel line under certain conditions.

 

I have a inline fuel filter right before the carb. I can rev the engine as much as I want the fuel level never changes. It seems to be getting plenty of fuel. I am thinking it could be the distributor. I have checked all vacuum lines and no leaks.

 

Check for vacuum leaks.

Are all of your intake manifold bolts tight?

Accelerator pump working correctly?

Automatic or manual?

If automatic, do you have the linkages connected and properly adjusted?

Full tune-up?

Undo the EGR vacuum lines and plug all the ports. Then, take it for a drive and see how it does. Could be a bad EGR valve.