ECM Fault?

[Bruce Plecan]

----- Original Message -----
From: Akselrud, Boris <AkselruB at moodys.com>
To: <gmecm at efi332.eng.ohio-state.edu>
Sent: Tuesday, December 07, 1999 10:07 AM
Subject: RE: ECM Fault?

Is this all still about a 747?.
If the problem is C/L, and feed back then just run O/L and see if that cures
it.
Grumpy


| I did better.
|
| I installed a cut out switch and a precision multi turn resistor which
| allows to dial an exact voltage of a  MAP sensor at the time (by voltage
| dividing between 0V and 5V). Then using the switch I substitute the
resistor
| instead of MAP sensor.
| Idle smoothens for a sec or two, then it roughens again and the engine
| always stalls after 10 sec or so.
| I think this is because ECM program is designed to continuously lean the
| mixture and watch MAP and O2 reaction. As soon as it senses lean
condition,
| It would compensate for it and add more fuel. Since It can sense no change
| in MAP while leaning up the mixture, it continues to lean it, until the
| engine stalls. That's why I need to complete my own fuel injection device
| and replace ECM with it. Then I can figure out if there is a fuel mode
which
| is making the engine happy.
|
| By the way this problem with the negative feed back loop(engine-ECM) and
not
| immediate engine reaction time is a common problem in negative feed back
| control systems. Rarely it is possible to implement it without causing the
| system to oscillate for at least a shortest time.
|
| -----Original Message-----
| From: Programmer [mailto:nwester at eidnet.org]
| Sent: Monday, December 06, 1999 7:16 PM
| To: gmecm at efi332.eng.ohio-state.edu
| Subject: Re: ECM Fault?
|
|
| Boris,
|
| Get a vacuum pump and hook it up to your MAP sensor. Slowly apply 15 in to
| 22 in of vacuum to the MAP and note if the idle smoothens out. Let me
| know...
|
| Lyndon
| -----Original Message-----
| From: Akselrud, Boris <AkselruB at moodys.com>
| To: gmecm at efi332.eng.ohio-state.edu <gmecm at efi332.eng.ohio-state.edu>
| Date: December 6, 1999 7:54 AM
| Subject: ECM Fault?
|
|
| >That's me again.
| >I am just one of those guys who don't take no for an answer.
| >
| >In short, I did find the anomaly with ECM fuel injector signals which is
| >causing idle roughness and idle rpm fluctuation. As you all know, in TBI
| >system two injectors are driven by pulses 1..1.2ms wide and spaced with
the
| >time interval required to make proper air/fuel ratio. What I found by
| >looking at the signal with an oscilloscope is that there is an additional
| >abnormal impulse approximately 0.1 .. 0.3 ms wide in between the normal
| >impulses opening the injector. This abnormal impulse comes and goes,
| >perfectly corresponding to idle rpm fluctuation. Even when I step at the
| >accelerator pedal, up to a 2500 rpm I can see the abnormal pulses and
| again,
| >they are not always there, they come and go with 1..2 sec interval.
| >I am also seeing about 70V spikes produced by inductance of the injector
| >coil and when I put zener diodes to cut them, the engine would barely
| start.
| >
| >I am also taking a second cut on the device I've designed to simulate
| proper
| >injector signals to the engine. My intent is to see if there is a fuel
mode
| >which would make the engine run smoothly. What I do is disconnect the
| >injectors wires and connect them to my device with help of which I can
| >provide accurate timing and play with duty cycle. However my current
| version
| >needs to be redesigned properly to absolutely prevent it from opening
| >injectors for more then  1.2 ms, otherwise I have had a little too much
| fuel
| >in throttle body on occasion.
| >
| >What do you guys make of it?
| >As you probably remember I am dealing with 1993 Cadillac fleetwood 5.7
TBI
| >
| >Boris.
|