99 Exped 5.4

Getting lean code bank 1.

Replaced vacuum lines pcv assy, cracked rubber.
Replaced that stupid pressure sensor
Replaced pass o2 fwd sensor
Installed 1 new injector...no change.
Replaced all injectors cause it needed it anyway.

Needed to be done anyway, just making the expedition better for long travel move.

Threw a code again.

Unplugged every injector and number 5 only one that did not change idle.
Swapped with known good, ran engine and disconnected all again. Still number 5 no fire injector.

Performed wiggle check.

What next?

 

Do you get the same result when you unplug the #5 COP?

Time to do a compression check on #5.

 

I would have thought that the coil pack not firing would cause a rich mixture. But nooooo, moved coil pack and another cyl went down. Replaced and all is good.

Thanks for the support.

 

To us old carburetor guys it does cause a RICH mixture. But the PCM doesn't read hydrocarbons cause it doesn't have a fuel sensor. It has an OXYGEN senor.

So if the PCM sees excess oxygen in the burnt gasses, it figures it needs to "add more fuel" to use this excess oxygen, which the PCM translates to "it running lean".

Just like us old carburetor guys think there is 'vacuum' within the intake manifold and when we go WOT we say the intake vacuum decreases.

The PCM thinks there is 'pressure' in the intake manifold (just that the pressure is less than atmospheric (aka Baro) pressure. When we go WOT the PCM says the intake 'pressure' increases , and that's why the PCM wants more fuel pressure to be able to inject fuel into that higher pressure area.

Sorry, sometimes I get carried away...........