Past 3-4 days ago I've had to put my foot down more than usual. In that time period engine once stalled, and today the revs got low and i could hear the engine, but the engine saved itself. (new air filter, spark plugs, coil packs (2), hard reset, some fuel treatment (lucas, b-12), and everything checked up.

 

MAF cleaned lately ?! Mine got erratic when it was gummed up.

 

I cleaned the MAF December, Do you think it should be dirty in that short period of time? I also cleaned the TB then too.

 

I wouldn't think so, but it never hurts to check.

 

Any other codes? Does sound like it might be the MAF if everything else has been checked.

When mine was on it's way out the car would hesitate under acceleration.
I cleaned it a few times, but the only fix was to actually replace it.
These are getting pretty old by now, so not entirely unexpected.

 

In stead of witch hunting possible failing parts, any 'live' OBD readout will quickly give you a direction if it is air, fuel or spark related, and allows to check the functioning of quiet a few sensors.
Without it, it is more like a casino.

 

+1
check the sensors you understand (IAT, ECT,...) then fuel trims

 

Cleaned the TB? If it is one without the vacume acutator (black cylinder on the top) it is not allowed to be cleaned.

 

XJR? Maybe you're down one fuel pump.

 

Are your battery connections tight? Are all the grounds tight? A loose connection could cause symptoms like you describe.

 

naturally aspirated v8 - 1 pump.
I ordered a OBD-II blutooth for my phone yesterday and got 2 day shipping It is going to be here tomorrow.

 

Good move.
You should be able to read and check the values, and see life progress of several main components and processes.

As a start, concentrate on the MAF and intake temp for air, the throttle position and short + long term fuel trims, the timing advance for spark, and the coolant temp.
One of those will probably be out of spec, which you can then hunt further.

 

what should be the readings?

 

MAF:
See attachment (for N/A)
Intake temp for air:
Ambient temp when startup, somewhere halfway between ambient and engine temp when stopped, lowering when riding again
Throttle position:
Between ~1% untouched, warm engine, till 90% full throttle
Short term fuel trims:
Depending engine load between -10 till +10, limit is some -15 till +15
Should come back close to zero when normal highway use
Should read zero when coasting
Left and right bank should be close to same
Long term fuel trims:
Should read within some -3 till +3, no more of -5 till +5 on a healthy engine
Should come back close to zero when normal highway use
Left and right bank should be close to same
Timing advance:
Need to check
Coolant temp.
Ambient temp when startup, some 90-95C on normal use, bit higher if load increases

 

Thanks for the information Eric appricate it.
Ok so here are the results all during idle.
STFT1- 0.8 - 1.6
Intake Temp - 38.0
Engine Coolant - 95.0
Engine Load - 15.7
MAF - 4.7
Intake Manifold - 21.3
Throttle - 0.8
Timing Adv - 4.5
Boost - 6.5 (vacuum i believe)

 

All was done at temp

 

I miss your Long term fuel trim, but guess that one is OK with such STFT.
Now you will get to check your MAF at the other conditions, and then just go driving and monitor whats going on, and see if you can figure out anything before or during the 'bad acceleration'.
Which program you use on your smartphone?

 

I tried my iphone but the good apps start at $15. I used my dads Galaxy s7 and the torque lite app.

 

Ok, if you choose a ''half-dial'' in Torque, you will get a gauge which also records the lowest and highest reading.
This is helpful to initially scan values, while still keep an eye on the road.

 

Ok while driving what should I be looking for?