[Shotimes] Re: MAF Voltage signals

Wed, 10 Mar 2004 00:15:43 -0500

Kerby can tell you what's Rotten in Denmark.

Kirk J Doucette
NESHOC President
Stormtrooper-97 White 

-----Original Message-----
From: Carl Prochilo [mailto:gr8sho@prochilo.myserver.org]
Sent: Tuesday, March 09, 2004 8:02 PM
To: Adam Parrott
Cc: TechSHO@topica.com; shotimes@autox.team.net
Subject: Re: [Shotimes] Re: MAF Voltage signals

I spoke to Pro-flow tech support today.  The person said that the
readings I mentioned are not correct.  He thought that the engine
control program might ignore the MAF signal and default to open loop
mode.  I also still have the original calibration data sheet.  The
MAF should send close to a 4.5V signal.  He suggested making sure
the MAF was cleaned and I took care of that.  Still same readings.

So something's rotten in Denmark and I have to pinpoint the cause.
One possibility the tech mentioned is to send the MAF back for
calibration, but I want to swap out the MAF first to see if that
changes things.
--
Cheers,
Carl Prochilo
1992 Ultra Red Crimson

Adam Parrott said:
> Carl,
>
> Was the 0.5v to 2.8v range with the Pro-M 77mm?  Are you running a
> chip or
> LPM with the MAF?  How the EEC will respond depends on the MAF
> transfer
> curve that it is using, the latter being determined by either the
> factory
> program or by a chip, LPM or tuner.  For a 55mm MAF, a 0.5 - 0.6v
> idle
> reading is somewhat low but not uncommon.  IIRC, Josh has said that
> a
> typical 55mm MAF on a NA V6 should idle around 0.8 - 1.0v at idle.
>
> Adam
>
>
> ----- Original Message -----
> From: "Carl Prochilo" <gr8sho@prochilo.myserver.org>
> To: <TechSHO@topica.com>
> Cc: <shotimes@autox.team.net>
> Sent: Tuesday, March 09, 2004 11:47 AM
> Subject: Re: MAF Voltage signals
>
>
> One more question about the observed measurements I mentioned below.
>  Given the range of 0.5V to 2.8V on the MAF signal, how will the EEC
> behave in terms of controlling the engine?  It certainly seems that
> engine is running rich and wanted to confirm that this is the
> expected behavior.
> --
> Cheers,
> Carl Prochilo
> 1992 Ultra Red Crimson
>
> Carl Prochilo said:
>> Alan, yes, I never bothered to see if the CEL was on when
>> unplugging
>> the MAF.  Verified that it does come on when removing the
>> connector.
>> And I
>> wasn't probing the correct wire either as you guessed.
>>
>> I never mentioned this in the previous post, but the MAF in
>> question
>> is a
>> Pro-M 77mm unit from circa 1998.
>>
>> Here's some more information.  To probe, I carefully exposed a
>> small
>> area of
>> wire by scraping away some of the insulation so I could get
>> alligator clips
>> on the wiring harness.  Using the EVTM schematic, I verified the
>> MAF
>> is
>> receiving the correct voltage, about 13.77Vs.  These are the thick
>> Red wire
>> for power and the black/green wire for ground, and are right next
>> to
>> each
>> other.  I then probed the light blue and tan wires.  These are the
>> signal
>> wires back to the EEC.  The readings here were not what I
>> expected.
>> At
>> idle, I'm seeing somewhere between 0.53V and 0.6Vs.  At WOT, the
>> max
>> I'm
>> seeing is about 2.7V to 2.8V, and SHOULD be close to 4.5V.  (If
>> the
>> signal
>> goes over 4.7V, I understand the CEL will come on again.)
>> Assuming
>> the
>> wiring harness is good, I probably should try a stock 55mm MAF and
>> see what
>> readings I will get.
>>
>> To do serious troubleshooting, the PCED refers to a breakout box
>> that I now
>> wish I had access to.
>> --
>> Cheers,
>> Carl Prochilo
>> 1992 Ultra Red Crimson
>>
>> Don  Donelson said:
>>>
>>>
>>> Correct .. your car will run with the maff unpluged ... the EEC
>>> when it
>>> detects the maff not connected will run in whats called " open
>>> loop mode"
>>>
>>> The EEC will default to a stragity that by passes your 0 2 senors
>>> ( the EEC
>>> wont read them ) and will create its own default fuel table.
>>>
>>> dond
>>>
>>>
>>> ---------- Original Message ----------------------------------
>>> From: Alan Fanning <awfanning@earthlink.net>
>>> Reply-To: TechSHO@topica.com
>>> Date:  Mon, 08 Mar 2004 20:06:42 -0800
>>>
>>>>She';; run without the MAF, but should throw a CEL. This happened
>>>> to me
>>>> this
>>>>weekend when I needed to move my parts car - I forgot I had
>>>> swiped
>>>> the MAF
>>>>to use on my other car for smog testing. Started and ran fine (in
>>>> driveway).
>>>>But the CEL was a giveaway that I had forgotten something.
>>>>
>>>>Sounds like, in your case, you may not be measuring the wire that
>>>> has the
>>>>information you're seeking(?)
>>>>
>>>>    Alan
>>>>
>>>>> I finally got around to the task of probing the wire mentioned
>>>>> in the
>>>>> attached note.  The way the voltmeter behaves it appears that
>>>>> the signal
>>>>> is
>>>>> open to the PCM.   I've observed that when removing the
>>>>> connector from
>>>>> the
>>>>> MAF meter, the engine doesn't behave any differently.  I also
>>>>> connected
>>>>> up a
>>>>> spare 80mm Ford MAF and still no difference.
>>>>>
>>>>> I would have thought the car wouldn't work that well, or at
>>>>> least rough
>>>>> without the MAF signal.
>>>>>
>>>>> The other item of note is that the fuel consumption of the car
>>>>> is high.
>>>>>
>>>>> Does this sound like a bad MAF connector?
>>>>> --
>>>>> Cheers,
>>>>> Carl Prochilo
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