A friend of mine has a 99 Explorer V6 4.0L SOHC. His check engine light has been on for a while so he tells me so I decided to check it out. Heres the list of codes I got:
P0300 Random Misfire Detected
P0301 Cylinder #1 Misfire Detected
P0302 Cylinder #2 Misfire Detected
P0300 Random Misfire Detected
P0301 Cylinder #1 Misfire Detected
P0302 Cylinder #2 Misfire Detected
P0303 Cylinder #3 Misfire Detected
P0304 Cylinder #4 Misfire Detected
P0305 Cylinder #5 Misfire Detected
P0306 Cylinder #6 Misfire Detected
P0171 System Too Lean (Bank 1)
P0174 System Too Lean (Bank 2)
P0300 Random Misfire Detected
P0301 Cylinder #1 Misfire Detected
P0302 Cylinder #2 Misfire Detected
P0303 Cylinder #3 Misfire Detected
P0304 Cylinder #4 Misfire Detected
P0305 Cylinder #5 Misfire Detected
P0306 Cylinder #6 Misfire Detected


I thought maybe his plugs were worn or gapped to much so I pulled one and they look almost new and the gap is within factory specs. What should I look for? The car pretty much runs fine. Except for a loud ticking which I have no idea what it could be...

 

I have a 1999 4.0L SOHC Explorer as well and it's the most troublesome engine Ford is making right now, in my opinion.

The two lean codes, P1174 & P1171, tell me that he should clean the MAF sensor to begin with. If that's not it, he may need to replace the intake manifold gaskets. The intake gasket is made up of 6 seperate rubber seals. When I pulled the intake off mine, every one was leaking. Plastic manifolds.... He should also check the PCV tube on the back side of the engine. The intake manifold may even be cracked. They are plastic after all.

As for the clicking, if it's rythmic tick,tick, tick, that is probably the spark plug wire grounding on the engine block. If you can get into a very dark garage and run the engine, you may be able to see the spark arching through the wire or out of the boot. To replace the spark plugs on this engine, you need to remove the passenger side wheel and fender well

Another thing about this engine is that Ford has a 7 yr/75,000 mile service program to replace both the front timing chain cassettes and the intake manifold gaskets. When you get the engine up above 1500 RPMs while accelerating, there is a very noticable rattle. That's the front and rear cassettes.

Be nice to this engine

 

any idea whats causing all the misfires?

 

I think the misfires are the result of either a dirty MAF or leaking O-Rings on the lower intake manifold allowing unmeasured air into the engine.

Owner Notification Program 00M12/Camshaft Chain Tensioner & Lower Intake Manifold Gasket Additional Coverage.

Ford extended the warranty on these parts for 6 years/72,000 miles on this Explorer. As usual, Ford didn't make much effort to let owners know about this recall so it may not have been done. If your friend takes their SUV into a dealer and asks for 00M12, it should be done, no questions asked, as long as they're within the mileage limits.

I think Ford's decision to replace these O-Rings was little more than a bandaid that is now going to become routine maintenance on this engine. Mine were leaking again about a year after they were replaced and it took sealant applied around each port to resolve this completely on my engine. Luckily, the 4.0L intake only has air flowing through it and comes off and goes back on in less than an hour, so you don't need to have a dealer replace these gaskets.

 

I had a similar set of codes just not as many but I did look into it right away so the codes didn't pile up. It turned out to be a simple vacumn leak. Check those hoses and make sure the PVC is seated correctly. Cleaning the MAP sensor sounds like a good idea too.

Good Luck

 

air leak or bad coil.

tom