Low 5v ref

[fixkick]

Hey there mr Fix

   Think we’ve got our wires crossed on the maf.  I do have 12v on the blue black wire to the maf. '
Got 7 or more at idle on the gray black wire back to ecu. 

SO True but you are not clear at all what pins measure what.
PIN2 the output pin of the maf can never read 7vdc.   Maf connected and back probed.
MAF pin Out list: (typ. 92-95’)  USA ! models.
 1--- Blue/black ---- Main +12vdc  power
 2--- Gray/black --- MAF output signal  1 to 5v , proportional  to Air flow.   B8     YOU MUST NOT HAVE 7vdc that is a super BAD MAF.
 3--- Black ---------- Ground.

pin 2 ,keyon not strated, is 1.0–1.6 volts
pin2 , idle 800 RPM, is  1.7–2.0 volts.
Pin 2 maf gun the throttle see 3v, never ever ever see 7vdc.

 

   I jus rewired the tps and pulled the o2 ect maf wires out of the ecu harness connector.
So far so good.
Def does run rich but... runs... so far. 
That is the whole purpose of LIMPHOME mode to run but is nasty burning, as  that is far batter than being stuck in a snow bank and a 50mile walk home.


Have had it go 3 weeks n then drop my 5v to the tps so we’ll see. 
   I want to prove it’s somewhere in those wires at least so I can start to narrow it down one at a tone somehow. 
  Something interesting is that it used to have a bad lag somewhere bout 3500 rpms before and now it doesn’t?   The MAF IS BAD< or is this in forced limphome forced by you?


WHY do this, if the MAF is bad the MAF is BAD, this must be corrected first. FOR SURE. and sure there are more problems SURE But the MAF is king and bad.
why go  past any DEAD MAF, it means no sense and the ECU will fully NUTS with that crazy 7vdc output maf,  pure hopless that. fix first thing.

Maybe one of the either grey wire back from tps or blue white wire??  Dunno. 
   Tested these wires and sensors every which way including pulling sensor wires out of ecu connector and sensor and load testing each wire.
Haven’t found anything wrong except the maf but even with those wires pulled from back of ecu still would end up dropping my ref. Sooo I got something else goin on somewhere. 
   Thought once this thing runs awhile hopefully.

I’d clip my tester to each sensor wire unplugged from ecu.   (do not do that, it is useless) we test sensor outputs running only.
Drive it around for awhile and watch for something out of whack.  (a useless in LIMPHOME test.)
It’s just so intermittent that seems I’d have to watch each sensor wire for a month In order to rule it out since it’s run just fine for 3 weeks n the past.
Something like that. Need a way to watch each sensor and wires for awhile and rule them out. 

   Or... tell me what you think.
Rerun All these sensor wires?  nah.
Guess could still be the sensors so maybe replace these too?   The MAF is bad and you are ignoring it.

  Where it’s at now if I drop my ref vol again then it must the ecu power or ground or sensor ground??? NEVER  (I F ECu has open ground or power 12v the ECU goes dead) totally dead.
5vref is a power supply inside the ECU and again, only 3 causes. (if dead 5vref, the ECU is NOT dead, you have spark and fuel and for sure limphome running) but 5vdc can be dead and car runs.
1: the sensor wires are shorted. if all read correctly the are not shorted, and if were the ECU reports them)
2: ECU bad.
3: or the 5vdc ref pin  wire is shorted to ground. (or far far far worse 12v) This ECU hates this pin to short and when does, blows up the 5reg, regulator inside.


   I’d love to take each sensor and plug them back to the ecu one at a time but I don’t want to blow another ecu.   use the voltmeter to see all sensors outputs,  and monitor for DTC errors at all times, (diagnostic jumper is harmless, use it)

   Thanks for your time and insight there mr

your welcome.!!!!!!

7v is bad maf, for sure. (connected assumed)  


a secret on mAFs, the pin 2 output is a VARIABLE current only output and the 1000 resistor,inside the ECU  converts that to voltage.!!!!!
this must be under stood first. or maf testing will fail.
on 1996+ cars the SCAN too tells me gram/s MASS air flow in the screen. G/S = grams per second flow, a very very important sensor that must work correctly and 7v is NOT IT.
if you fail to keep the maf connected pin will LIE to you for sure.

proof here, bench tested.  see my bench resistor here,?   the maf can only tested on car, or like DID below.