[Gmecm] RE Tweaking Asynchronous BTW

Sun Sep 10 00:35:06 UTC 2006

Hello: Not really sure what BTW even is?? Black smoke = excessive fuel, I
guess we all know that Ha!.  A couple things come to mind, If you have a
fuel pump test pigtail (ability to run fuel pump without any ignition on)
Apply 12 volts to pump test pigtail and see if the injectors or pressure
regulator is puking fuel into the TBI. The pump should run and no fuel
should appear anywhere in throttle body area. I assume that you can
verify regulator pressure setting someway??? I had a problem where there
was air being sucked in from the lifter valley through the intake
manifold to head mating surface, this made the O2 sensor read lean all
the time and applied more fuel when it was not needed, just a thought. If
it is sucking air in through the lifter valley it will pull oil in also
and show up on the plugs, pull them and read them, see what they look
like. In my case i had to pull the intake, regasket it, use high temp RTV
and retighten. As i tightened each bolt slightly beat the intake into the
lifter valley area with a rubber mallet, tighten and beat on it until
torqued to specs, that fixed that problem. The temp sensor plays a big
role in fuel mixture, make sure it is working properly. Because the ECM
deals with low voltages dealing in tenths of volts make sure all
connections are in very good shape and your engine block is grounded
properly, this can raise big trouble with electronic controlled engines.
The ECM is only as smart as the data it receives from sensors. Bad
reading from sensor = bad happenings from the ECM.  I have several 1"
wide braided ground straps on my engine to chassis and the ground wire
from the battery goes directly to the engine block. Make sure all the ECM
grounds go to the engine block and are in good shape. I have a scope so I
can actually see things and how good or how bad they are. My engine still
has some minor tweaking problems only because I have not had time to get
to it. With a scope you can easily see the O2 sensor working and can see
if the mixture is being controlled properly by the ECM. Because you seem
to be running rich from what I can gather I would satisfy yourself that
none of your injectors are leaking and the "o" rings are sealing properly
and the regulator is not leaking or is not regulating properly. Until you
are satisfied that the engine, sensors, injectors are in working order,
you will tear your hear out trying to program around a problem with the
mechanics. That is about it. I wish you luck
Darryl...
On Sat, 9 Sep 2006 18:02:49 GMT "matthew10_5 at netzero.net"
<matthew10_5 at netzero.net> writes:
> Thanks Darryl.. 
>  Maybe a bit more info would be in order. I built this engine 2500
> miles ago. I put every thing new inside and out. It has been 
> overbored
> has a cam a little taller than stock. I thought that maybe one of 
> the
> new sensors might be bad , so one by one they have all been 
> replaced
> again. The wiring harness was replaced and the speed sensor. The 
> TBI
> unit is from a 350 cid and therfore has larger injectors . This 
> larger
> injector size facilitated an 8% lowering of the VE tables almost 
> across
> the board (so far). The timing tables have been tweaked only 
> slightly
> mostly to stop preignition. I had taken my van to a Chip maker to 
> start
> with because at the timeI was unfamiliar with reprogaming the ECM. 
> When
> the engine was first fired it would hardly run blowing clouds of
> unburned fuel from the tail pipe. When I picked up the van it was
> better and it would idle now but was still blowing black smoke 
> under
> what I now know as WOT. After taking the van back 3 times for the 
> same
> problem, and after an $800 bill, I deceided to try it myself even
> though it didn't have the Dyno. Everything the shop did has been 
> undone
> except for the increased fuel pressure regulator. For some reason 
> they
> thought this was part of the problem. Anyway I bought all of the
> equipment, (except the Dyno and Sniffer) and have burned 27 EPROMS 
> so far.
>  This is why I am now at the place it must be something else. All 
> the
> sensors and the IAC are working properly. The BLM is still low at 
> this
> point in Real time using a data logging program. I have extensive
> records of in car actual driving conditions, even through the Rocky
> Mountains.
> Back to my ORIGINAL QUESTION , what is "ASYNCHRONOUS BTW" and how 
> does
> it affect the VE tables. Is it nessessary or should it just be 
> disabled.?
> If your reading this Steve, do you have any comments?
> 
> 
> 
> From: "dgilbert78 at juno.com" <dgilbert78 at juno.com>
> Subject: Re: [Gmecm] Tweaking Asynchronous   BTW
> To: gmecm at diy-efi.org
> Message-ID: <20060908.105104.3679.893120 at webmail16.lax.untd.com>
> Content-Type: text/plain
> 
> Hello: make absolutely sure that the MAP sensor is seeing proper
> vacuum. No 
> kinked hose, no mushy hose, no partially carboned map port in the 
> TBI
> body. 
> Restricted (delayed) vacuum to the MAP will act like bad acclerator
> pump in a 
> carb. Make sure that is absolutely perfect befort re programming. 
> May
> have to 
> remove TBI and rod out the MAP vacuum port, these become carboned 
> and
> gummed. 
> Good luck. Spent many hours finding that one.
> Darryl..
> 
>          Tweaking Asynchronous BTW
>                 
> Date         :         Fri, Sep 08, 2006 10:04 AM
>                 
>                 
>                         
> 
> 
> I have been unable to remedy the stumble problem with my 305 using
> the 7747. I have readjusted the timing tables, the VE tables. 
> Although the motor runs great it still stumbles on takeoff in open 
> or
> closed loop. The system goes rich under partial throttle between 
> 800
> and 1100 RPM without going into WOT inrichment. My question is 
> about
> the asynchronous BTW handles in three tables. One table is for 
> Maximum
> and one is for Minimum and still one is for RPM.
> One blog that I ran across tells off fixing the stumble problem that 
> I
> have by setting one of these table values to "0". Can someone shed 
> some
> light on the asynchronous BTW modes? What is it, and does it 
> overide
> the VE table, or work with them, or none of the above? Which 
> setting
> would potentially remedy my problem. Any Thoughts?   Matt
> Darryl..
> 
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