I have a Ford F-150 86 5.0 EFI V8. It came with a computer when I bought it. I have changed the fuel pump relay, valve cover gaskets(oil leak), The in-tank fuel pump assembly, and the MAP Sensor so far. I ran the computer before replacing the MAP, and came up with code 22, and it turned out to be the MAP by the book, so I changed it, and got pass 11 after that, no problems. Then, I went on to the running test, and got the following error codes:41,13,77, and 25. In the book, when I look up 41, It says to check the PCV valve, fuel pressure, to check ECA with DVOM, and to check EGO sensor with DVOM. Also, to check TPS and HEGO. Code 13 tells me to check ISC and ECA, along with the vaccum lines. I have checked the vaccum lines, they are all in dam good condition. This was one of the first things I did because I know for a fact that if one of those lines are bad, You will run rich.Code 77 also deals with the ECA. Code 25 has to do with the Knock (Detonation) sensor, and the ECA. I have no clue what the heck the ECA is and where it is located, or any of the other capitalized abbreviations. Im 16 and just bought this truck, and have redone the interior, and primed the body. Its a beauty flareside, and really want to get it going perfectly. ANY help would be GREATLY aprreciated. Thanks

 

The code 77 and 25 are easy. The code 77 means you didn't perform the "goose test" During the test the engine will slow and run rough. Then it will suddenly smooth out, and then you will see one pulse signal. After this single pulse, you are supposed to smash the accelerator to the floor and then release it. This should get rid of those two codes.

The ECA is the main engine computer.

Code 41 means the engine is running lean. Code 13 means the idle air bypass solenoid could not slow the engine down. These two point to air getting into the engine from somewhere. You said you checked the vacuum lines. One thing that sometimes happens is a leak in the brake vacuum booster, letting air enter the engine. One other thing that happens, particularly on the older FI trucks like yours, is the intake plenum gaskets leak. I would pull the air intake off, and replace the gasket if they look bad.

 

I replaced the air intake plenum gasket, and there are NO vaccum leaks, its all perfect. It just runs with a loss of power and rough. What else can be going on?

 

Bad fuel could be...how long was she sitting before you bought her...

have you run a few tanks of high octane gas through it....


also reset your timing........to see if you can get her to run smoother with more power.....

 

like i said, i dropped the tank and replace the fuel pump in the tank, and the external one, and the filter, and have put NOTHING BUT premium gas in the truck since ive bought it. (a year now) it just runs awesome when it wants to....

 

Did you replace cap, rotor plugs and wires as well...

Also outside the codes, How is it running what is it doing that its running less then perfect..

Stalling , idle irradic or dies out wont restart when hot

missing?

 

all new plugs air filter, distirbutor, cap, everything. timed perfectly. for about 2 weeks, itll run shaky in 1st and 2nd gear, then drop to about 600 rp, in the third gear, causing very heavy vibration and roguh running, and poor gas mileage. then, itll run perfect for a little while.

 

Did you check voltage at the TPS...

It should be under 1volt but not less then .5 volt at idle
(make sure its under a volt , this could cause poor gas economy(eg:if voltage is at 1.43 volts at idle it would waste alot of gas..)


also check voltage while pulling throttle all the way open
voltage should increase gradually from less the 1(idle) to 4.5-5v(wide open)


also clean your egr valve while your at it......may be sticking from time to time causing your problem...