Trying to apply logic which never seems to work with car problems like this:
The Facts:
Car runs perfectly at times and then suddenly it runs like crap with wandering idle, hesitation on acceleration, stalling at idle.
It seems that after it stalls and restarts it could go either way running good or crap again.
No Engine light is triggered.
Codes thrown are; P0102 MAF Low Input (connections/supply?),
P0507 Idle Speed too high (Wandering idle?).
P1571 Immobilizer - Open Circuit / No Signal
Since its my second new MAF I think I can rule out a faulty MAF as the source of the problem,
A faulty ground on the MAF or electrical is still a possibility but a low probability based on common issues I read here. Also I drive over some pretty bumpy roads and the faults do NOT correspond with vibrations making/breaking electrical conductivity so I'll rule that out as well for now.
Replaced AOS which had died and perhaps precipitated these issues?
Replaced Pre CAT sensors but no change there.
New Spark plugs and Coils look good and would be causing missfires if damaged and I am not getting misfires so cross the ignition section off the list.
New Fuel Filter, Checked Fuel pressure in the shop but not while driving and experiencing the hessitation so Fuel Pump is still a possibility.
The Fuel Pump relay can also be added to the potentials list since it is related.
Fuel flow is also good in the garage so that eliminates obstructed fuel lines and filters.
New Air Filter, better check the duct work for any obstructions just in case.
I have heard that turbulence at the MAF can cause problems and is why EVO intake folks sometimes experience MAF problems.
The battery had died while in the garage so it might have been weak, but its replaced now.
The computer ECU seems to work fine in every respect and the car still starts so the Computer is not fried,
however cold solder joints in the computer or loose ground connections to sensors is still possible but a low probability.
I did jiggle all the connectors leading into it and no changes were evident.
Vacuum leaks and smoke testing did not reveal any obvious leaks but that does not mean there is not a crack that could open up under real driving conditions and pressure, however nothing blatant was revealed as it was smoked from the intake side and through the Oil filler side with no leaks showing up under a few psi of pressure.
The only high probability items I can think of is the Fuel Pump and Ignition switch as many folks have done it from what I have read.
Those items don't seem to be monitored by any fault codes either so perhaps those should be my next efforts.
I have read that ignition switches going bad can produce all manner of strange issues but have absolutely no evidence or history pointing to the switch as suspect.
I have found a diagram showing the MAF pin-outs so I think I'll check that before buying more parts just in case its a faulty sensor ground connection or an out of spec supply voltage.
Looks like I'll have my 90,000 (Its only 72k on my odometer) mile service done by the time I replace all the wear and tear parts !
Should be good for another 10 years if the engine holds out.