1987 F-150 300 in-line 6, 4 speed Manual
Idle is fine slow takeoff is ok speed tops out at 35 mph. If you try to push it faster than that, it falls on its face.

If you press acc to the floor at a stop it does the same thing, actualy sounds as if it has died, let off gas and it comes back to life and idles fine...... Stumped on this one, and very little cash to start changinh parts in hopes of finding the failed part...

 

Sounds like a plugged air filter (easiest to check) or collapsed catalytic converter (in the exhaust).

To check for cat converter problems, unhook the exhaust at the manifold and see if it is better.

 

Could also be a fuel related problem. Check filter and fuel pressure.

 

Just went and tried a couple of things...

1. Ruled out clogged air filter.
2. there is no cat. anymore (someone ran pipes)

havent verified fuel pressure yet. will try tomorrow.

Here is a twist for ya...
The more vacum lines I unplug the faster the rpms get mabee a clue their.

I am sorta stumped for now....
Just bought the truck (had no trans when I bought it) so I dont know its history, I do know that it has sat-up for several months.

any and all help is much apreciated as I am new to Fords

 

Check the timing with SPOUT connector removed. I've seen trucks that idled fine but ran slow/rich be timed w/o SPOUT removed and be too slow. If you check codes you should tell if pcm has stored a code for running lean or rich which could be HEGO (oxygen) sensor problem. Be careful with the vacuum lines, they will break. You can buy tubing at parts store and connectors if you have to replace any but it is generally black, not color coded. Best bet is to check timing, fuel pressure (gauge is ~$40), and scan for codes. Reply with that info and can get even more help.

 

> Check the timing with SPOUT connector removed.

Ok, at the risk of sounding stupid...... Just what is a SPOUT connector?

 

The SPOUT connector is shaped similar to a spade type fuse but larger. It is close to the distributer and plugs into a connector with 2 wires. This gives the pcm control over timing. While you are checking/setting timing you don't want the pcm adjusting reverse of where you are putting it. Newer models have it near the pcm connector on driver side firewall but yours should be within 4-6" from the distributer. If you set timing with it in, timing will be slow and truck will idle fine but run rich at higher rpms because spark is too late. Exhaust manifolds will overheat and glow orange and crack. Just unplug it and use the timing light. When you tighten the distributer bolt back down, just plug SPOUT back in.

 

Thank you, will try to narrow this thing down some more this evening.