Hello fellow Ford Truck Enthusiast,

I would like to introduce my self and the 86 f150 I just acquired. I'm a welder and I've been a gear head all my life. I'm regularly a volkswagen guy but no stranger to Fords. I drove a 62 Galaxie for about 5 years. I just got back into a Ford when I sold my VW rabbit pickup, needed something a little more practical for work.

Now on to the truck. Its a 1986 F150 "4x2" with a 300 six and a four speed manual trans. As far as i can tell its bone stock and hasn't been "hacked up" "back cobbled" or "abused" by any unskilled mechanics. It is old though and has a few issues at the moment. Thats what brings me to the FTE forums. I hope to get some help bringing this great truck back to its former glory.

Here it is the day after I picked it up. Thats my fiancé creeping in the back ground. lol.

 

Those old sixes never die but the electronic systems that run them do like to give trouble. You probably have the one with the computer in it that controls the carb and the timing.

 

Welcome to the forum the guys here are a lot of help when you need it.
Dave ----

 

Not sure what the problem is but the engine is missing and won't rev past 3000rpm.
acts the same way in neutral and under load.
I checked the compression, getting 140psi +or- 5psi on all cylinders after 4 or 5 cranks.
I checked and reset the timing at 10* btdc, after that it revs to 3000 before it would only rev to ~2200 rpm.
I also checked the cap and rotor and they look fine.
Next thing I was thinking to do is throw a vacuum gauge on it and check for leaks and for the exhaust being plugged up.
If its not that maybe the cam is worn out? Is it possible for the cam to jump time on these engines?
I'm not familiar with the 300 six so if anyone can suggest where to look next or help in any way I would appreciate it.

 

Did you miss my post above? If you think you have a timing problem, the timing is controlled by a computer on your six. There were a few that were not, and some people convert it over to get rid of it. You can verify this by looking at the distributor. If it doesn't have a vacuum line going to it, then it's computer controlled.

 

I saw your post. When I checked the cap and rotor I also checked the coil and the tfi module. All checked out good. I also plugged in a working tfi module from a friends truck.
If it's not the module on the distributor should I move on to the carb controller?
Where is that located?

 

Now I don't know the "computer controlled" trucks too well but it would control the carb & dist timing from what I have seen posted.


With out checking books I know most computer controlled cars/trucks when checking/adjusting timing you need to un-plug or jump out pins to lock timing. Other wise the computer will try and adjust timing to what "it wants".


If the truck has been sitting something could have gotten into the exh and plugged it up. Vac gauge may show this could also drop the front pipe to see if this makes a change.


I know someone will ask does the computer give any codes? I don't know how to pull them but it may guide you to a fix.
Dave ----

 

Reading the codes on that truck is simple. $30 ford obd1 code reader from just about any parts store, and count the beeps to see what code it's throwing if any.

 

Ford Ranger - Testing EEC-IV Equipped Engines

 

Does everything look original under the hood or are there a lot of plugged off and loose vacuum lines and wires? Consider this setup sort of like a fuel injected engine, it will run but not correctly if there is a lot of stuff unhooked. The computer uses info from various sensors to determine how much to advance the timing to the TFI module.

Not sure exactly where the computer is on your model, but the first place I would look is right in the middle under the dash right over the tranny hump area.

 

Thanks for the help guys. I figured it out. Threw a vacuum gauge on the engine and immediately knew the exhaust was plugged up. I took off the muffler and it was full of catalytic converter substrate. Engine runs great now!
Also did a little tune up after that.
Now I just need find some F.I. exhaust manifolds to redo the exhaust.
Thanks again for all the good tips. I'll be sure to update my thread as I continue building this truck.

 

Good to hear you found the reason for the limit on RPM.


I forgot back then the cats did come apart and plug mufflers.
The other thing they did was plug and run red hot catching grass if parked over or heat up the floor and set carpet on fire.
Dave ----

 

Awesome truck! It has the same cream/metallic sandstone paintjob as my 86 F150 Flareside with a 300Six and 4 on the floor. Welcome to the forums, I'm in the same boat as you. Worked on tiny european cars (triumphs) but have only every driven fords - A 78' Ranchero and a 05' mustang. The truck thing is new to me too but a lot of fun!

How many miles are on the motor?

 

I love the paint scheme on this truck and all the two tone trucks from the 70s and 80s.
The odometer says 99xxx I'm sure it's rolled over once.

 

Since the truck needs a new exhaust I'll be upgrading to these split manifolds.

I'm waiting on the y pipe and new cats to arrive. I can't wait to hear it with the new exhaust.