When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a 1991 F150 with a 5.8L. I changed the spark plugs, rotor and cap a few months ago and the truck ran great. The truck sat for several months and when I tried staring it it ran real rough with black smoke. I let her run until warm and pulled the codes. I have replaced the MAP sensor, Throttle Position sensor, EGR control solenoid, EGR value, air charge temp sensor and I will replace the engine coolant sensor once I locate it. I have started the truck with the items above replace and it still is running rough with black smoke. Any help would be appreciated???
Possible faulty fuel regulator.
If my scenario is true, you have too much fuel pressure, more fuel than can be burned.
Might be a good time to stop throwing parts at it without further investigation.
You will need a fuel pressure gauge to monitor idle fuel pressure.
I suggest not driving it until you get it sorted out. If you have a rich condition you're going to carbon up the motor quickly.
If you catch it soon enough (without continuing to run it/drive it) you can salvage the plugs and burn off the carbon from a longish drive (to maintain heat and proper burn).
Start with checking fuel pressure then go from there.
STOP changing parts. Change parts that are due on the maintenance schedule, and those that fail a published test. But only replace them with the BEST available parts (not necessarily the cheapest, or quickest), and only with parts that pass the same test that the previous one failed.
With the engine idling, pull the Red vacuum line from the fuel pressure regulator (FPR) and inspect for the presence or odor of gas.
Try pulling the vacuum line on the fuel pressure regulator and then turn the keyswitch on and see if fuel shoots out of the vacuum port on the regulator....
If the vacuum regulator is good and no fuel is squirting out of the vacuum port Id try pulling the distributor cap and spraying wire drier inside ..
Another thing to try is cleaning the battery terminals......In our trucks the battery terminals are very very important in an EEC-IV system.....
If you look at these two grounding wires......They look like average run of the mill ground wires but thats far from the situation.....
These two wires are for the ECU...One goes to pin #40 and the other goes to pin #60.....Theyre supposed to go to the battery direct but thats where Ford put mine so I added a 4 ga grounding wire to it....
Those two grounding wires serve a an important purpose and thats to do a comparison between an unimpeded path to ground against the ground that runs to the MAF on the MAF circuit also to the other sensors/solenoids and helps eliminate ghost readings from the sensor when the body grounds to the engine block throwing off the readings which lead to thrown codes.......
Another thing that goes direct to the battery is the ground wire for the EEC relay so look for that one too and thats a little trickier to find..Mine was on the heaer panel ground for the headlights...If your EEC relay and fuelpump relay are older than 10 years old I would replace those because as they get older they get weaker plus the contact pads inside the relay that create the connection get oxidized which causes a voltage loss and the fuel pump relay is triggered from the EEC relay and 12v is sensed by pins 37 ,57 also #19.......Wire #22 is what breaks the connection to the fuelpump relay after you turn the key and the fuelpump primes the fuel system with the correct fuel pressure...Its also an internally controlled ground..
In my other truck I have a dedicated grounding system that removes EMI radiation interference without using destructive methods simply using ansitropic crystals........Its whats melded together in the center of the handmade copper strap is what makes them work....Its a propreitary mix of metals....LOL..........
Another possibility is your ECU got water inside either the ECU connector or inside the ECU itself and caused the capacitors to fail....
A faulty coolant temp sensor or IAC sensor or plug for either will cause the black smoke too of the sensor tells the computer the coolant is of air temp is colder out than it really is......
Sure looks like an electrical hack job to me.If a vehicle is properly maintained, these electrical alterations are never required and open up possibilities for future problems.
...simply using ansitropic crystals........Its whats melded together in the center of the handmade copper strap is what makes them work....Its a propreitary mix of metals....LOL...
I'm glad to see the "LOL" - for a second there, I thought you were serious. But if you're gonna use big words (even in a line of BS that deep), you should learn how to spell them correctly.
And all that crap in your pics is ridiculously counterproductive. All the return (ground) wires should be connected as directly to the battery negative terminal as possible. But NOT to a craptasmic side-terminal battery; the standard top-post design is far superior. And in a cheapo battery with dual terminals, the side terminals are NOT equivalent to the posts. They have inferior connections to the main terminals. Check the manufacturer's specifications.
10-09-2022, 11:49 AM
91 5.8L rough idle and black smoke
