High Block Learn

[rr]

This almost sounds as though you either have a leak in the exhaust allowing
air in before the O2 sensor, or, you have a misfiring plug that is causing
excess air in the exhaust.

Either would fool the ecm into adding more fuel. Maybe drive around
a bit, with some cruising and pull all the plugs. They should have a
story to tell.

BobR.

Don Burns wrote:

> Shannen
>
> I guess the signature is somewhat misleading so I'll clarify. The car
> is an 86 Fiero GT that has a crate 350TPI with a 5-speed in it. As for
> having the tools, I have always worked on my cars to some extent and know
> enough about
> engines to muddle my way through successfully. But, I have never ventured
> into ECMs and the sensors that drive them, until now. My education and
> background professionally is in RF circuit design, all analog. I am by no
> means knowledgable when it comes to digital electronics. You guys leave me
> in the dust when you talk about your compilers, assemblers, etc  ;-)
>
> A guy in Chicago did the transplant for me a year ago but I have been out
> of town so much I have not had time to dig in to it. He's built a couple
> hundred of these things. The engine is set up so it is equivalent to
> something like a 90 L98, Camaro/Firebird/Vette. I am using an AutoXray tool
> - fairly cheap but seems to do the job. For this car the tool is configured
> as a 90, 8th VIN=8, 4th VIN=F. This is how the builder told me to configure
> the tool and I am following his instructions.
>
> What I know about ECMs and EFI I have learned in the last several weeks out
> of books, both from Motorbooks. One of the books was mentioned in a
> bibliography on the DIY-EFI website and I have found both loaded with
> information. Thanks for the recommendation. My actual experience working on
> EFI? Almost ZIP.
>
> I have replaced the O2 and MAP sensors, only because I happened to have
> both in hand. There was no good reason to replace either other than to see
> if there was any difference in how they worked with the ECM. There was no
> difference. The O2 sensor was clean, no evidence of contaminants.
>
> Here are some numbers from the scan tool I think are important. If I have
> left something out that is important please tell me. All data taken at idle.
>
> * O2 sensor toggles from 350 to 700 mv
> * Block Learn is 160 and doesn't move
> * Block Learn Cell = 4  (I don't understand this number or its meaning)
> * Integrator  ranges from 128 to 135, sometimes a little higher
> * Idle Air   10 to 13 steps (The idle is a little a little unstable right now
>         and I suspect the IAC needs to be pulled and pintle and seat cleaned
> * MAP   1.25 to 1.30 volts
> * Knock sensor  5
> * Knock retard  0
> * Injection pulse width  2.0 to 2.1
>
> The base timing for this engine is set at -8 degrees.
>
> I have also run a can of throttle body spray cleaner around the top of the
> engine looking for vacume leaks.
>
> One more piece of data that might be telling: At highway speeds this car
> does 21 to 22mpg, almost a 2:1 difference. No, I have not taken any scan
> data at highway speeds simply because I have not had anyone to drive while
> I am playing with the tool. Maybe this should be next, huh?
>
> I am presently waiting for a guy in San Diego who sees 18mpg city with the
> same car and engine to get back to me with comparative data. There is
> nothing like seeing some numbers from an engine that doesn't have the
> problem.
>
> This was awful long, but I don't know how to come clean in 50 words or less.
> Thanks in advance for any suggestions or tips.
>
> Don
>
> >There's more to this than you're mentioning.  I'd bet on it.  The
> >first clue is that your siggy says "86 GT" and your post says "O2 and
> >MAP sensors are OK".  86 tpi is MAF...
> >Next clues are that you have a "mild chip", access to a fuel pressure
> >gauge and a scan tool, and know enough about efi diagnostics to try
> >forcing the ecm to substitute values for disconnected sensors.
> >So tell us what you've done to the car, and what you've checked so
> >far, and you'll probably save 2 days worth of cat-n-mouse games. ; )
> >
> >I may be mistaken, but if that fp reading is at idle, it may be a bit
> >high for a stock 86 tpi.
> >Shannen
>

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