LTFT for Bank 1 and Bank 2 are ranging from -3 -> 20%. Measured while idling and then nearing 3000 rpm.
Does this indicate a vacuum leak ? Thank you.
2006 S-Type V8 VDP

 

When big & when small?

 

History:
Day1: No CEL. Sometimes Stalling when starting. Action> Replaced Battery.
Day7: Code Appears (PO171/0174): Codes come & go Action> Firestone checked and said the breather pipe to PCV is leaking.
Car started stalling while crawling during heavy traffic, stop&go drive thru ...driving. Engine turned off and had to be restarted
Day20: Code Appears (PO193, PO171/0174): Action> Took to another shop. Diagnostic of PO171/4 said to replace the PCV valve. Replaced Valve and PO171/4 codes disappeared. P0193 Remained.
Day 30: Replaced the Fuel Rail Pressure Sensor. Stalling Gone !!
Day40: P0101 shows up with P0171/4. Car drives fine, no stalling. 18 mpg.
I have attached the Idle Readings and then during driving.

 

I'm having trouble with your graphs. How about:

Start your car & get it up to temp.

Record the LTFT & STFT for banks 1 & 2 as values, not graphic.
Record values at idle. While still parked, increase revs to 1500, hold steady & record values. Repeat at 2000 rpm & then at 2500 rpm.

 

The value will only be a single reading / one-instance. The spread of 'value' per time is not possible. The graph is the only way to capture for a span of time.

 

What I explained was the standard way to read fuel trims as you asked if you had a leak.

Hope you get it sorted.

 

The CEL went off after i started pressing on the gas. I have captured some stats
Idle/CEL on



IDLE/ CEL OFF



Difficult to steady RPM. Below are some captures at a steady rpm. CEL Off.

 

If engine was hot the MAF is probably misreading - dirty very probably & might clean.

With an air leak you'd expect the LTFTs at high revs to drop near 0.

If the engine wasn't fully warmed up then forget all the readings.

 

Thank you. Engine was definitely warm in the readings taken at 8:57. The CEL has not returned yet. I will get the MAF clean.

 

Please see another round of data, engine is warmed up. I have not taken any action yet. Is it better to change the MAF sensor or clean it? Thank you

 

I'd try cleaning it. Don't use anything that leaves a residue (e.g. avoid WD40!!) and the wires are THIN so don't touch.

 

Thanks. What should be the expected MAF sensor behavior / reading in the outputs ?

 

I can't see how those graphs help. Read other threads on your codes and follow them. You're drowning in data.

 

Also, should you decide to replace the MAF at some point, be sure to get an OE or OEM (that means Denso) from a trusted source. There are lots of counterfeit parts out there, to be found on that famous o-line auction site for example. Also, you might want to include your general location in your profile; it might prove helpful if additional help is sought in the future.

There are dedicated MAF cleaning agents available that leave no residue. Assuming it is available in your location, CRC makes a good one...