No Code Misfire

[Paddyk]

2008 4.0 4x4
I’m having a heck of a time diagnosing a no code misfire and would appreciate any feedback as to how to get this resolved. The condition is always present ( all engine temps and loads. And very noticeable at 1500 rpm)

I’ll quickly list what I have done so far.

-Changed coil, ignition wires, plugs, & fuel filter. These were all original parts so they were over due for replacement (All OEM parts purchased at local dealer)

-checked for leaks with propane, none found.

-checked compression & averaged approximately 210 psi all cyl.

-spark has been checked at all ignition wires and spark plug gap checked.

-test fuel pressure.
65 psi while engine running and approximately 60 engine off.
*However..The pressure dropped 10 psi in under a hour with the engine off.*
Had a local shop pressure clean the injectors at the fuel rail.

Checked for codes and misfire counts using Forscan. No codes or counters.

*Forscan O2 test shows a “Fuelsys error” on bank 2.
I have attached the screen shot of the test for bank 1 & 2 .
The 02 sensors are original so they are most likely in need of replacement however I’d prefer to find the cause of the problem first.

I’m “guessing” that there may be a fuel injector leaking down due to the 10 psi drop as mentioned and that it could be located on bank 2 because of the o2 error.

Or is it just an sensor error only? I’m over looking something?

Any advise will be much appreciated!

 

[franklin2]

Can you pull each sparkplug wire off one at a time and narrow the misfire down to a certain cylinder?

 

[Paddyk]

I did try that and did not see any difference from any of the cylinders. The engine vibration was increased the same amount per cylinder.
But I will revisit that one more time but with the scan tool monitoring the engine while taking a cylinder offline.
‘Thank you for your replay, I appreciate it.

 

[RonD]

Gasoline engines just have 3 parameters
fuel
spark
compression

Once those are confirmed and vibration is still present then its not a misfire

Assuming vibration can be felt without vehicle movement

I have had fan clutch cause engine vibration
COLD engine
Remove fan belt from crank
Start engine
See if vibration is gone, if so replace fan clutch

Harmonic balancer, crank pulley
Deteriorating rubber can cause vibration

If automatic, failing torque converter can cause vibration, should eventually break the flexplate

4.0l SOHC in 4x4s originally had an internal balancer(2001 and up), lower engine driven by timing chain
These were dropped in most 4.0l SOHC engines in 2005 but could have one in 2008
Seen here: https://cimg0.ibsrv.net/gimg/www.fo..._9bf65966347d5849b20698f27f5bb7cec4cb2fbe.png
Located on passenger side of engine
Never read about these failing, ever

These were added when Live Axle was first used in 4x4s, to counter any vibrations from always rotating front drive shaft