Well, I'm confused by this...

[holyford86]

04 ranger with sohc 4.0 and manual trans, throwing codes for cylinder 1,2,3 misfire, multiple misfire, misfire on startup, and has a bank 2 lean code. So far I've cleanded the mass airflow sensor because it had an oil film on it, and checked for vacuum leaks, also unhooked one of the upstream o2 sensors to make sure that they were hooked correctly side for side. Maf is showing a flow rate of 4ish grams of air at idle and goes up steadily with throttle application. Someone has been in here before me and appears to have changed plugs, wires, head gaskets, oxygen sensors, and coilpack. Runs OKish when cold and idles like crap when hot but clears out when held at 1500 rpm air charge temp and coolant temp also seem fine... what am I missing here? It has to be something stupid.

Sent from my XT897 using Tapatalk

 

[RonD]

Because it is running poorly I would believe it is a lean issue not a sensor issue.

4.0l SOHC are becoming notorious for leaks in the PCV valve's vacuum line, at the elbow, so I would pull it off and check it closely.
You would think this would effect both banks, but it often doesn't.

When engine is cold computer runs a rich fuel mix until it warms up.
Which is why it runs a little better cold, another reason to believe the "lean" codes.
Fuel pressure on the returnless system should be 65psi.
The computer can not monitor fuel pressure it just assumes 65psi, so it opens injectors for a length of time(dwell) based on that fuel pressure.
If fuel pressure was 40psi then fuel mix would be leaner than it should be.
O2 sensors would see the leaner mix and computer will increase the dwell(open time) but it will only increase it so far and then set the code because something is wrong for dwell to be that long.
Again you would expect low fuel pressure to effect both banks, but one side may be effected first.

The air plenum from MAF to upper intake manifold is a ported vacuum area, so a leak in this tube will effect fuel/air mix, remove it and check it for cracks and holes.


The engine work was probably related to timing chains, these were a weak point on the 4.0l SOHC

 

[adsm08]

Actually Ron, that PCV elbow is a weak point on many Fords. On the 2.0 Z-tec it collapses and produces a rough idle, and they break and leak on many engines including the 3.8, 3.9 and 4.2 in addition to the 4.0. They usually have a life of 10-15 years. I think we are seeing a rash of them from the board's SOHC-owning members right now because they are getting to the age where they usually fail.

And yeah, you would think it should affect both banks, and sometimes it does, but the 4.0 is placed so that it mainly feeds and effects the one side.

 

[holyford86]

Alright, I'll take a look at these areas, thanks for the info

Sent from my XT897 using Tapatalk