Thread: EMS thinks lean - why?

GKN are a reputable brand. HS's were the OEM suppliers I understand. I could be wrong. Doubt the GKN's will see you wrong. It says they're OEM. So I'm prepared to be corrected.

Originally Posted by TheTree

These are some numbers I found

At Idle...................... 20 kg/hr (5.5 g/s) ± 3 kg\hr (8.3 g/s) (^)
At 2500 rpm............... 61 kg/hr (16/9 g/s) ± 3 kg\hr (8.3 g/s) (^)
At 3000 rpm............... 90-100 kg/hr (25-27.8 g/s) (*)

22-25kg at idle,90-100kg at 3000rpm in neutral,engine hot all loads off.

At Idle 20 ± 3 kg/hr
At 2500 rev/min 60 ± 3 kg/hr ..

Steve

These numbers have an error. Since MAF values are so important, I have corrected them here:

At Idle...................... 20 kg/hr (5.5 grams/sec) +/- 3 kg\hr (0.8 g/s) (^)
At 2500 rpm............... 61 kg/hr (16.9 grams/sec) +/- 3 kg\hr (0.8 g/s) (^)
At 3000 rpm............... 90-100 kg/hr (25-27.8 grams/sec) (*)

Bibliography:
(^) - RAVE & MAF Values
(*) - P38A P38 4.0 HSE MAF SENSOR DATA Is it working? Whats wrong? Please help. - Page 2 - Land Rover Zone

Probably stuff you have already looked at, but had a couple of thoughts on a couple of the problems being mentioned...

Does your MAF have the big O ring in place? If you never had one, you might not know its missing...

Also any chance your dropping power under rev's could be related to a loose and/or damaged Crank Angle Sensor?

Probably way off the mark but some of the comments reminded me of times i had problems in the past.

I Think I covered this is another thread
...good to close out here. The shudder was due to a a cracked flex plate in the trans. This completely let go and destroyed the AT pump with complete loss of all drive. Fitted replacement trans and all solved. Fitted new MAF and LTFT etc back to normal. Towed 2T boat 14 hours over hills last week with no issues...other than fuel economy shooting up to 18L/100km!

Bad news about the flex plate. At least we all know not to ignore the signs you mentioned.
Regarding your OBD software - is it Torque?
Are you using a bluetooth transmitter or hardwiring to the OBD port. If so which one are you using. Two bluetooth transmitters I have bought off ebay have proven to be useless.

With you second screen shot you can see that your old MAF is underreporting air mass by at least 20-25%[ the update speed on yr MAF values depends on how good the ELM chip is inside your transmitter]. Assuming it is correctly reported, the metered injector pulse width/ fuel mass will be less.
Actual air mass will be more.
BTW, the ECU knows the theoretical air massflow from the Throttle Position Sensor because the engineers have loaded air mass vs throttle position into the backup fuelling maps. If you were to cut the feedback wire from the MAF to the ECU, the ECU will default to those theoretical air mass vs TPS values for fuel metering to get you home.
In your case, your ECU is "hanging on" to the incorrectly reported air mass value. Eventually as the reported MAF value drifts further towards a non-sensicle number compared to TPS your ECU will then flag a bad MAF.
As you have observed, the result of the incorrect air mass flow report is the faithful o2 sensor reporting lean - both are at fixed low voltage in your screenshot showing a fixed lean reporting status. In closed loop the LTFT must keep the STFT close to zero and so the long term Fuel trims drive a rich command by increasing injector pulse width by 25%.
Assuming that your software is getting accurate values from your OBD interface then the symptoms of a bad MAF were there in the evidence.
Now that you have a new MAF you need to record the correct values at idle, and various constant speeds (MAF,TPS, fuel trims RPm, calculated load and O2) File this away. Can you record a data stream with your software?
In the future if you see the same fuel trim story and the MAF/ TPS values are spot on from your records,you will now know you have an intake leak or fuel pressure issue.
When your car is running well you must take a data snapshot for a few minutes at each load condition for future trouble shooting.