New member needs help

J Norris jwn at sgi.net
Fri Nov 20 17:04:53 GMT 1998


BTW, what do you mean by ray A/D value?

Jason

Scot Sealander wrote:

> J Norris wrote:
>
> > I finally broke down and got a Diacom and recorded the event.  When it
> > happened at WOT, my O2 reading dropped to 0 and my integrator climbed
> > to 180 while my inj. pulse width was 9.5ms or so.
>
> There is some good information there if you know how to use it. Keep
> reading.
>
> > My TPS voltage was .55 at idle and 4.98 at WOT.  The ECM will not go
> > into open loop PE mode at this high of a voltage.  At this high
> > setting, the ECM was trying to maintain a 14.7:1 air fuel ratio.  I
> > readjusted the TPS to 4.63 volts max and BINGO!  The ECM goes into open
> > loop rich condition.
>
> "Trying to maintain" is clear.  But look at that O2 volts!  Look at the
> integrator.  The ECM is seeing a lean condition *WHILE IN CLOSED LOOP*.
> It is trying to so something about it (maxing the int), but it can't do
> enough.
>
>
> > Now, the million dollar question is could the high TPS voltage at
> > WOT cause the lean condition I am experiencing?
>
> It can at minimum contribute to it, and it probably the cause.  The ECM
> listing has high and low voltage limits for the raw A/D value the TPS
> supplies.  The exact values for these limits and associated test
> conditions will vary with the particular calibration used.
>
> So here is the important thing. If the A/D result it is out of the
> "normal" range, it IMMEDIATELY sets the TPS bad flag, but may not set
> the error code if the bad value isn't present long enough.  If the TPS is
> flagged bad, a substitute default value is used, and this value is not
> enough to set PE mode.  So it stays in closed loop, and *will not* enter
> PE mode.
>
> > The fuel pressure is fine (37 psi at idle 45 psi at WOT) but I never
> > had an opportunity to check it while the seemingly lean condition was
> > occurring.
>
> The psi delta is right.  The 45 psi sounds familiar, didn't someone just
> post that there injectors shut down at 45 psi?  Lean at WOT?  Hmmm.  Got
> those kind of injectors?
>
> >From another post:
>
> > Its an aftermarket chip but the stock one reacts the same way.
>
> They should.
>
> > Everyone I talked to says that there is no reason the ECM should leave
> > PE mode at that voltage.
>
> Are we still talking TPS voltage above 4.9 or so? If so:
>
> Everyone?  Now you know who NOT to ask. :-)  Big grin!  As said earlier,
> the ECM *will* leave PE if the TPS is so high that it is out of the
> normal range.
>
> > Something else my be causing it.  The guy who made my prom, Fastchip,
> > suspects the MAF.  He said the ECM will substitute values it thinks
> > airflow should be when the MAF is bad.  He also told me that swapping
> > out MAF's is the only way to tell.
>
> BTW, what are your MAF airflow values at WOT?
>
> Ok, now are we still talking lean at WOT?  I thought I read that AFR was
> correct once the TPS was reset to the proper range.  If it was, then the
> MAF is probably Ok.
>
> I still see some concern for the lean condition when not in PE.  There
> may be a simple explanation, but if it runs right with the TPS set where
> it belongs.....use it.
>
> If I don't understand this correctly, keep typing!
>
> Scot Sealander    Sealand at clarityconnect.com




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