2003 Ranger misfire has me stumped

[Rearanger]

What kind of O2 graph voltage readings are you getting? Should range from about .9V to .1V with about .45V as the midrange.

 

[mdnelson86]

O2 graphs on both banks are doing exactly that. They look fine to me.

The short fuel trims are just staying above or below 0. not switching positive and negative.

 

[Rearanger]

From your earlier post Bank1 is running lean and BK2 running rich. I don't know what Ford's parameter is for setting a code.

Why don't you trace the vac leak first then see what happens.

 

[mdnelson86]

Ok, I have a small vacuum leak in the PCV tubing, but don't believe that to be much of an issue. New parts should be here in a day or 2 to fix that.

I unhooked the brake booster and stuck a vacuum gauge in its place. The gauge is bouncing rapidly between about 7-8 inches of vacuum and 0 (maybe even up to 1 to 2 psi of pressure)

Is this low and pulsing vacuum because of the missing cylinders and rough idle? could it be exhaust back pressure or something of that nature? I also notice when looking at live data on my scanner that the ignition advance is running up around 25-35 degrees. seems very high to me.

 

[Rearanger]

It's been a while since I used my vac gauge so I usually need to refer to my vac gauge reference sheet.

Here's a link which you may have already found. Plenty more on Goggle.

 

[mdnelson86]

Another detail I've just noticed. When I have the truck running, the rear passages of the upper intake manifold are getting very hot to the touch. This is with the motor running for just a few minutes before the truck has even gotten up to temperature. I'm not sure if that is normal, but it seemed odd to me.

 

[mdnelson86]

Just thought I'd post an update if anyone was interested or reads this in the future.

Turns out the problem was the lower intake manifold gasket. As careful as I was putting it together, and as good as I felt about it, the gasket must have slid just a tad and wasn't sealing on the lower end of the cylinder 5 and 6 intake ports.

I had a real "ah-ha" moment the last time I took the upper intake off after I had it running for a while. The intake runners for 5 and 6 were covered with oil. So it was either the intake manifold sucking oil from the lifted valley or valve seals. Since the heads were rebuilt with new valve seals, I was leaning towards the intake gasket. Pulled it apart and sure enough there was oil in between the gasket and head at those points. This also explains why I couldn't find a vacuum leak since it was internal to the lifter valley. Put it all back together with fresh gaskets and the truck runs as smooth as can be now.

Thanks to everyone for all the help and input!