Hi. I recently bought an 86 f150 with the 4.9 v6. The guy I bought it from changed the manual fuel pump right before I got it. The truck ran fine the first day, then started to act up. The truck is running very rough and smells rich. It acts like its missing so I replaced the plugs, wires, cap and rotor. Still runs bad.*

Ive changed the oil and there was some fuel in it from the fuel pump going bad. The auto choke is fully open after a few minutes of running and the pcv valve has plenty of suction. So, they both seem to be operating correctly. Im not sure what else to check so any help would be great.

 

That truck should have a computer on it, so you need to go to the sticky on pulling the codes, here. The computer will tell you what it is seeing as the problem.

 

Gary's advice is right on and you should follow it. I will add something, though. The 4.9L really dislikes any vacuum leaks and at 28+ years old, the rubber and plastic lines get brittle and crack. Also, any vacuum ports [carburetor or manifold vacuum tree] which have been capped, often lose the cap. Check all these and replace as necessary.

Grab the air cleaner with both hands and see if you can gently rock it back and forth. If it moves, then the carburetor is likely loose. There are two nuts which hold the carburetor to the EGR adapter. If loose, there is a vacuum leak. These tend to vibrate loose. If they are tight, but the top half of the carburetor moves, then the 4 screws which hold the two halves of the carburetor together have loosened.

Finally, if the 13 or so bolts which secure the intake and exhaust manifold to the engine block are loose, there will be a vacuum leak.

Let us hear back from you. Good luck and welcome to the forum!

 

Thanks for the replies. Im gonna buy a obd1 scanner tonight and mess with it. It seems like it's dumping to much fuel. It has a very rich smell and the new plugs are covered with fuel. Thanks for the help, Jeremy.

 

If anything goes wrong [bad sensor, loose wire, missing emission component, etc.] regarding the feedback system, then the computer places everything in a "safe" mode, so no damage occurs. That means that the timing is locked at the static timing [usually 10 degress BTDC] and the carburetor mixture solenoid swings to the rich side.

This equals poor performance and very high fuel consumption [8-10 mpg; ask me how I know?].

Our Moderator, ctubutis, shared this link with me, previously.

http://www.therangerstation.com/tech...ry/OBD_I.shtml

 

I don't think these are OBD-compliant. IOW, buying a scanner will be a waste of money. You need to follow the instructions in the link.


Edit: WRONG! See Chris' clarification below.

 

Gary,

His 1986 should have an EEC-IV which AFAIK can be scanned by handheld scanners BUT the same procedures still need to be followed, e.g. KOEO, CM, KOER codes taken correctly, step on the brake pedal/turn the steering wheel when told to during the KOER test, etc.

To my knowledge, the EEC-III stuff was all pre-1984.

 

Thanks for the clarification, Chris. I've edited my post.

 

So, I used a code reader and all I got was 14 and 18.
Code 14 is the ignition profile pickup (pip) circuit failure and code 18 is loss of tach input/idm circuit failure/spout circuit grounded.
Im gonna read over my haynes manual and see if I can make sense of these codes. Any other help is appreciated.

 

I tested the pip out voltage on the module on the side of the distributor and got 0 volts ac. The manual said I should have around 5 volts ac. Any input would be great. Im getting desperate and think I may go ahead and replace the distributor and the module. Thanks in advance for any help

 

I don't think a TFI-IV dist has an voltage output, just a DS2 Dist with the magnetic pickup which does create a small AC sine wave.

 

The TFI ign module is famous for heating and failing, also the 14 signal lets you know the signal from the diz is shady at least intermittently. This sometimes can be solved by checking and cleaning the wiring associated with the mounting of it. You CAN replace the diz internal PU which fails, but it's a job. Read up on the "TFI module relocation concept". Ford DID re-locate the diz module remotely in the 90's after being involved in the famous lawsuits over the thing failing at in-opportune moments.

Of course if you don't need to retain the TFI distributor for emission inspections reasons, a simple revert to a late 70's "duraspark" conversion may benefit you. Many people take that approach to solve the many issues.

 

After messing with the truck all day I think im going with the duraspark conversion. It seems like everything will be pretty easy to find except the wiring harness. Anybody have one they wanna sell? Thanks for all the help.

 

Look down the carb throat with a flashlight while it's running. If you see liquid fuel dripping into the engine, you have a carb problem(besides the other problems). Your float level might be too high and raw fuel is spilling into the engine. Just takes a minute to pull the aircleaner off and check it. Don't get caught in the fan or the belts.

 

If you want to retain your present TFI coil and it's wiring, which many have done, you may do so this will solve part of your parts search and help with some of the wiring. User "jimsrebel" has done this as well and recommends the use of a GM HEI module in place of the usual ECM on the fender-well. If I were you I would research this as an option, and build your own harness good luck

This read should be informative:

http://www.gofastforless.com/

https://www.ford-trucks.com/forums/1...ctors-diy.html