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<DIV><FONT color=#000000 size=2>Most respected folks,</FONT></DIV>
<DIV><FONT color=#000000 size=2></FONT> </DIV>
<DIV><FONT color=#000000 size=2>I am in search for a resolution to my problem. I
presently receive an intermittent Code 33 from my system (87 305 TPI TransAm).
I've tried throwing parts at it (pigtails, relays, ECU, TPS&MAF sensors),
tried adjusting it (TPS, hammer and nails;<), etcetera. </FONT></DIV>
<DIV><FONT color=#000000 size=2></FONT> </DIV>
<DIV><FONT color=#000000 size=2>The MAF appears to get good power supply voltage
(coincident with initial firing of fuel relay and steady 12-14v after startup),
and the MAF seems to give good readings (ballpark 400-700mV @ 700-1200rpm)
initially. However, if I monitor the signal voltage from the MAF, a bauble
occurs at seemingly random times (often very soon after start-up), where the
voltage jumps up to 3.2v or so (or was it 2.8v or so, similar to voltage
measured with MAF power supply cut off). This is quickly followed by a Code33
set. To eliminate, the ignition usually must be cut off for 10 seconds or so
prior to restart. Once it sets, the voltage stays around the 3+v level (if I
remember correctly...it may still vary with engine speed, though). I've gone 2-3
days without coding, other times it's every start-up event. Sometimes as it
codes, it gets real rough and rich till the code sets, then it smooths
out.</FONT></DIV>
<DIV><FONT color=#000000 size=2></FONT> </DIV>
<DIV><FONT color=#000000 size=2>If I disconnect the MAF, the signal wire to/from
the ECM reads 5v. If I pass this to ground through 100ohms, it reads about 0.5,
indicating 1kohm internal resistance. Anyways, I'm at my wit's end from a
tinkerer's perspective. I'm ready to start looking at it from an EFI ECM
perspective. </FONT></DIV>
<DIV><FONT color=#000000 size=2></FONT> </DIV>
<DIV><FONT color=#000000 size=2>I have some minor modifications on the engine,
and this problem seemed to crop up after head rework and header installation. I
am not prepared to spend much cash (Haltech or such), but I am ready to spend
attention and time to learn what can be done to better diagnose and/or alter
(burn new PROM myself, perhaps?) the present system. Initially, I suppose my
thoughts lean towards a home-grown Diacom-type serial interface, or a swap-over
to a more versatile/supported ECU for read/write activities. </FONT></DIV>
<DIV><FONT color=#000000 size=2></FONT> </DIV>
<DIV><FONT size=2>I see this as a potential for gaining knowledge, but if anyone
has a basis of experience from which they might be able to help with my present
issue rather handily, it would be much appreciated. Right now, the MAF and
accompanying relays have been removed to keep the car from stumbling and
stalling each time the Code33 sets. I assume this throws the car into 'limp-home
mode' (which is really rather smooth), but this is unacceptable for any extended
period.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT color=#000000 size=2>I'm a 30-year old engineer (PhD Chemical) with a
fair electronics background, and I'm willing to listen. <FONT color=#000000
size=2>I hope someone here can give me guidance, or redirect if there is a more
appropriate forum. I've been searching for some time now.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2></FONT> </DIV>
<DIV><FONT color=#000000 size=2>Sincerest thanks,</FONT></DIV>
<DIV><FONT color=#000000 size=2></FONT><FONT size=2>-Craig Moates</FONT></DIV>
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