HELP !!!
This is what i have, i just purchased a 1992 Ford F-150 4.9L I6 from a guy down the street, he had it mothballs for a few years due to both fuel sending / pump units going bad at same time, knowing what was involved to just replace sending / pump units, he replaced both tanks complete, than he did a basic tune-up - dis. cap, rotor, wires, plugs, new radiator hoses, belts, oil & filter, fuel filter, thermostat & antifreeze.
Got it up and running, took it to a car wash and pressure washed the engine bay, THAT'S WHEN IT HAPPENED !!!, Engine started to run badly, hesitating, missing, loss of power, poor accelerator, he is a backyard mechanic, he replaced the following components-
Air Intake Sensor
ECM Engine Control Module
Engine Coolant Sensor
EGR Valve
EGR Valve Position Sensor
IAC Idle Air Control
ICM Ignition Control Module
MAP Sensor
O2 Sensor
Most if not all of the vacuum lines
I have confirmed the parts mentioned above have been replaced.
None of this worked, cold start the engine purrs like a kitten ( during this time if you did not know anything about this engine you would not think there was a problem ) but 10-15 minutes into engine warming up to operating temperature THAT'S WHEN IT HAPPENS !!!
With all this there is NO CHECK ENGINE LIGHT ??, I did not believe him at first, but it is happening, i am also just a backyard mechanic, i have done most of my own repairs through the years, rebuilt engines, but this has me stumped. HELP !!!!

 

Moisture has probably got into someplace where it shouldn't.
Sometimes ,,,with a little patience, if the vehicle ran good before the bath, give it some time to dry out and you may find there is nothing wrong.

Now comes the problem,,,,,,,,,,,,,,,,,,,, If all the known good parts were replaced after the bath, anything is possible now.
I am only telling you this because I have been there many times and the first time , all I could ask is , what did I do now ?

If you can , leave the hood open for everything to have time to dry out. Sometimes it takes a few hours and other times it took a couple of days, but we are much wiser now and are more careful where we direct that water cleaning.

 

Hanky

All this happened about 1 year ago, the previous owner told me to he did just as you mentioned about opening the hood and let it dry out, and i have taken my own cars & trucks to the car wash and have done the same thing and nothing has happened.
I have hope that this is something small that i am just over looking, because when i start the engine, up until it starts running bad, it is a smooth running engine.

Jeff

 

After a prescribed period of time, and when certain other conditions are met , the computer starts taking info from the O2 sensors and coolant sensor and now tries to control injector pulse width , which is the amount of fuel that goes into the engine. If incorrect info is coming into the computer the computer doesn't know it is wrong , but responds accordingly. The idea is to determine which parts of data could be wrong.
There is a sweet little tool made by Thexton, #443 that will save you loads of time and allow you to get key on engine off,& key on engine running codes.
All you need is the code chart. In addition when you follow the directions it will automatically do dynamic testing with the engine running and give you any codes it finds.You didn't need a scan tool to repair those early Fords the computer did everything for you and not too many knew this.

 

Sounds like you need to pull the plug wires and dry out the boots inside. My experiance is that you have mositure trapped in the spark plug boots! Happens all the time on these models.

 

Forgot to tell you to make sure you dry out the inside of the cap and the wires connecting to it also.