Hello all, I’m a new member here. I got some great help on another project from mopar1973man (thanks again brother) on another forum and figured I'd come over and try to get help on this nightmare.I will try to keep it short and sweet. I am working on a 2006 base model Ranger 4x2 with a 3.0 L auto for a friend. After more low compression problems than any vehicle should have in a lifetime ( bad valve seats), we have just replaced the engine AGAIN. The replacement is from an ’06 Taurus. I finished the install and took it on a 15 mile test ride. 1 mile from home the check engine light came on. Cyl. 6 misfire.Checked compression on a couple of cylinders obviously #6 included and they were at 160 PSI.The replacement engine was pretty complete so I have a few test parts.I swapped #4 and #6 spark plugs. No change, it’s not the plug.I replaced the plug wire. No change, not the wire.I installed the Taurus ignition coil. No change, not the coil.I replaced the entire set of injectors with the set from Taurus, with the thought that the flow rate could be different but if they all match it should still run good. No change, injectors are OK.I also swapped the crank and cam sensors and last but not least I tried seafoam in the fuel and oil with the thought maybe the valves in #6 could be sticking. Still get the light EVERY time.I was a line tech mostly at dealerships for about 25 years so I’d like to think I have a good idea what I’m doing but, I don’t have access to much tech info and don’t have a good scanner anymore. ( Stupid thieves) That being said, I despise just swapping parts without knowing they are bad before I replace them but I need to get this thing back on the road and you do with what you have right?Their isn’t much left that I can think of that could cause a misfire. I don’t want to condemn the computer without absolutely knowing but what else could I have missed?Any thoughts? Thanks in advance for any help or ideas you may have.

In all honesty, I think you definitely need to just get a good scanner on it.. I'd definitely lean towards an ecm issue. Are the Fords still batch-fired injectors, like they were back in the EEC-IV days?You've replaced most everything related to spark control, with the exception of the ECU. Given the fact that you've replaced the wires, I know it's not a COP ignition, so that really only leaves the ECU.. Are you running the Ranger or Taurus ECU?

Check for vacuum leaks. If there is a vacuum port near the troubled cylinder the lean mixture will act like a misfire. I had this same problem on MoparMom's 1996 Dodge Ram with a P0306 code well changed the plugs, wires, injector (#6), still had it. But come to find a hairline crank on a vacuum line now its all gone.

The 3.0L were known for heads cracking and head gasket issues. I'd concentrate there, with first doing a leakdown test.

Ok so first of all, Thanks for the ideas guys.

I am running the Ranger ECM and it has a coil pack (1 coil with 6 high tension posts)

I would like to do a leak down test but don't have the tester and all I have for a scanner is the ole Snap On red brick MT2500 and a code reader. Can't justify spending the cash on a new one because I don't bend wrenches for a living anymore.

Since I was here last I have done the following.

Checked fuel pressure. 62 psi spec is 60 to 65 psi

Changed the fuel filter.

Added seafoam to the fuel tank.

Added Marvel Mistery oil to the crank case.

Used GM engine top end cleaner, (I've had GREAT luck with this in the passed)

Added 91 octane fuel.

Driven the truck 50 miles, with absolutely no success.

I do notice it pinging when I drive it. I am able to make the light come on every time within a quarter mile. If I floor it it shifts at 5k rpm then I count to 3 and there it is EVERY time. I drove it to work babying it like crazy and made it 12 miles before it came on.

While sitting here racking my brain I keep thinking LEAN misfire!!!!

I just went outside and pulled cyl #5 & #6 plugs. #5 is dark with a slight black soot look to it (kinda rich)

#6 is white. I'm right it's lean! I haven't been able to find any vacuum leaks but wtf else could it be? I think I am going to go and get a plug 2 steps colder and see if that works but even if it does why is it lean???? Any ideas ?

I WILL BEAT THIS TRUCK!!!!!!!!:banghead:

Ok so first of all, Thanks for the ideas guys.

I am running the Ranger ECM and it has a coil pack (1 coil with 6 high tension posts)

I would like to do a leak down test but don't have the tester and all I have for a scanner is the ole Snap On red brick MT2500 and a code reader. Can't justify spending the cash on a new one because I don't bend wrenches for a living anymore.

Since I was here last I have done the following.

Checked fuel pressure. 62 psi spec is 60 to 65 psi

Changed the fuel filter.

Added seafoam to the fuel tank.

Added Marvel Mistery oil to the crank case.

Used GM engine top end cleaner, (I've had GREAT luck with this in the passed)

Added 91 octane fuel.

Driven the truck 50 miles, with absolutely no success.

I do notice it pinging when I drive it. I am able to make the light come on every time within a quarter mile. If I floor it it shifts at 5k rpm then I count to 3 and there it is EVERY time. I drove it to work babying it like crazy and made it 12 miles before it came on.

While sitting here racking my brain I keep thinking LEAN misfire!!!!

I just went outside and pulled cyl #5 & #6 plugs. #5 is dark with a slight black soot look to it (kinda rich)

#6 is white. I'm right it's lean! I haven't been able to find any vacuum leaks but wtf else could it be? I think I am going to go and get a plug 2 steps colder and see if that works but even if it does why is it lean???? Any ideas ?

I WILL BEAT THIS TRUCK!!!!!!!!:banghead:

Based on your findings my SWAG is a cracked intake or blown intake gasket. Had the same problem on a '98 Dodge 1500 w/318 would only spark knock when it was warm, pulling a load up a hill. was a bear to find. Intake runner for one cylinder was cracked. never through a code. The 3.0L ford V6 where ____ engines after some miles were put on them.

My 5.9L Dodge Ram 1500 (V8) had a blown intake gasket on the plenum it was also sucking in engine oil and air from the cam valley.

It was a afternoon project to pull the nose of the engine apart to change the gaskets but no more issues with misfire codes.

Thanks again for all the thought provoking ideas to everyone who gave me any input.With that being said… I WON!!!! :thumb1:WooHoo What I finally found was a partially plugged pre cat. My theory on what was actually happening is #4 and #5 were not able to expel exhaust gas and therefore were running rich. This caused the computer to lean the whole bank then #6 would lean misfire. I guess the length of the exhaust manifold must have been the difference. It runs better than ever and I finally get to tell my friend to get it out of my driveway.

Good deal, Dana!