I have a 1999 (month: March) Ford F150 with the 4.2L V6 XLT Reg. Cab Long Bed 120000 miles. Original sale was in the state: MD.

As I was driving to work Friday (July 6th) I picked up a missfire condition. At the time I was at about 1700 RPM and 25-30 MPH. It was during very mild acceleration.

Anyway, once I felt the vibration I prob. made it 0.1 miles before I decided to push it into a conveniently close Advance Auto Parts. The man there read the code and it was (Random multiple misfire) P0300.

So, I had my truck towed to my house where I started to diagnose.

Since I didn't know where the missfire was I decided to use water to see which cylenders were hot at the manifold. It turned out that the entire drivers side wasn't fireing... I scanned the computer again and this time I picked up a P0304 P0305 P0306... This fit what I had found just moments before. 4,5,6 misfire.

I did much research on the issues to discover what would cause an entire bank to misfire. I found two issues. Clogged cat. converters or a stuck open IMRC actuator.

The easy thing to do was to disconnect the cats. Once I did this I got 4&5 to fire but cylendar 6 was still misfiring. Hmm... I need help here. I think I can rule out (but not completly rule out) the IMRC because 4 and 5 are now working. I know the cats prob. have something to do with my issues and will need replacing?

I have spark at all plugs, and using an automotive stethascope all the injectors are clicking. I might add that the plugs were fairly gummed up 4,5,&6 getting worse in that order.

What do yall think?

 

Motorcraft plugs and wires? Ever changed the coil pack?

 

The coil pack is new. (3 days old) (Could have bought a bad one though)
and Bosch Plat. IR Fusions (3 years old). (The Bosch plugs helped my mpg's a fair bit and I have documentation to prove this.)

Swapped around plugs and wires from #2 to #6 and the issues still persists.

Everyone I talk to says it's either wires or the coil pack.

Gonna get new wires anyway because it is time for them.

Any experience with E3 plugs? If the plugs messed up?

 

Get those Bosch plugs OUT of there and put Motorcraft platinums in it. If you replace the wires, use Motorcraft.

Rockauto.com:

Motorcraft SP504 plugs $3.19 each
Motorcraft WR5702 wire set $37.99

OEM is best on these vehicles.

 

Those parts are on the way. I also purchased a Motorcraft fuel filter because it has been 15000 miles since I last changed it.

 

Ditto on the Bosch plugs. Something about the 4.2 and Bosch plugs just don't like each other.

I had one go bad on me with about 20,000 miles on it (truck had 120,000). Was a PITA to diagnose, so I drove around with a moderate, intermittant misfire for a while, but no codes. Replaced O2 sensors, coil pack, wires, cleaned the MAF, new fuel filter, etc... I figured it was not the plugs since they were almost new...Could not believe how bad it would run without throwing a code! Scanned it several times...

Got real bad and finally threw a code, showing a misfire on #6. Replaced just that one plug with a Motorcraft in the Auto Zone parking lot. Ran great! Bought 5 more Motorcraft. Cleared codes and no more problems.

 

I installed the Motorcraft plugs and wires today. The result was a smoother feel but that is about it.

Still have missfire on 4,5,&6 with all things put back in spot.

Every plug I removed is in poor condition. The stock plugs that lasted 104000 miles were in much better condition upon removal.

I also have a terrible tapping noise on the driver side of the engine. This makes me wanna think mechanical issue. Burnt valve? (Need to do a compression test ... maybe in the morn) Have a feeling like I might be ripping the heads off soon.

Should I start tearing er apart at this point to check such things as EGR and IMRC operation?

 

I do believe I have found my issue!

Did the compression test and had ZERO compression on #6. Took the valve cover off to discover a broken valve spring.

So, now you know!

Thanks for the help!

I'll keep the Motorcraft parts in 'er.

 

Fixed!!

Swapped out all of the valve springs (from the Ford dealership) and valve seals (Vicotor Reinz <= Ford has given these the Q-1 [best] recomendation for seal replacement).

Painted the valve covers and install brackets Ford blue.

Turned the key... (Vroom or whatever) waited several minutes for the oil to reach the rockers then took her around the block to help all the solvents and oils to burn off the engine.

Now I smile!

ok enough of that...

Gonna swap out the fuel filter and install a new Wix air filter.

Last... I will change the oil using Pennzoil Platinum SAE 5w30 and Wix oil filter. Yes the Wix is actually a better filter. It has better oil flow than the motorcraft does. (bobistheoilguy.com)

(Wix and Victor Reinz are both involved with the Dana corp.)