Hello All,

Im new to this forum, but Im hoping someone on here has had a similar issue and can point me in the right direction. I have an 04 ford ranger 3.0 V6 with 115,000 miles that is throwing faults 304 and 316. I started with changing the plugs and coil pack and cleaning the crank sensor. That didnt fix it so I swapped the spark plug wires to make sure it wasnt the wire and verified that the #4 wire was sparking. Next, I checked the injectors and found the the #4 injector would just drop out so I changed it. Still didnt fix the problem. The problem with the injector dropping out seems to only happen after the truck has idled for several minutes. The injector will be firing then it will drop out for like 10-20 seconds causing the engine to run rough then it will start firing again and run smoothly. I compression tested the engine and found cylinders 1,2,3 around 150-155 while 4,5,6 where at 110, 110, & 115. I believe that 4,5,6 are low but Im not sure that it would cause the injector to intermittently stop firing. Finally, i unplugged the computer and plugged it back in and the codes went away and the engine is running smoothly again. Not sure if it was just a poor connection or if there's more wrong. Any ideas?

 

Welcome to the forum

There is a TSB for what you have

Unfortunately it requires replacing both heads on the 3.0l, wish it was a simple fix

In 2004 to 2006 Rangers with 3.0l there were issues with Exhaust Valve seat recession

I posted the whole TSB in this thread: https://www.ranger-forums.com/2-9l-3...-p0316-144859/

Your symptoms are classic, with the low compression on one bank or cylinders, yes the computer will shut down the fuel injector to test if that was the problem for the misfire, it can't do that with spark, so computer sets the misfire code because it can't tell if its fuel, spark or compression related, it stops adding fuel full time to prevent major engine damage, if a cylinder is not firing then it is dumping that raw gasoline into the exhaust manifold and Cat converters, not good, also could cause pre-detonation, making a hole in the piston

When engine is running and warms up the exhaust valves get good seal then bad seal because of the bad valve seats, a static compression test will show slightly lower compression, but with engine running it will drop down below 100psi causing the misfire
Expected compression on cold 3.0l Vulcan is 160psi, it runs at 9.3:1 ratio


You could confirm bank 2 valve issue by adding some oil to cylinders and repeat the compression test, psi will go up, but if it doesn't get up to 150psi like on the other bank then it is a valve issue, not rings.

I wouldn't do just the one head, pretty big gamble for the work involved