Wierd Instant Shut Down Sympton

[Bill Robinson_]

I have a 92 Legacy Turbo sedan with a 5-speed tranny. The other night I was
parked for about four hours in weather at about the freezing point, so the
car was cold. It started right up, then within about three seconds, the
engine just quit. I started it again and it did the same thing again. I
repeated this about twenty times and finally it did not shut down, so I sat
until it was fully warmed up and drove home without incident. The check
engine light never came on to signal a computer error code. I checked the
computer codes when I got home and it showed that it was free of error
codes. The next day I was parked for about an hour and it did the immediate
shut down trick once. It has not done it for the past three days. Can
anyone shed light on this phenomenon??

Bill Robinson
92 USA Turbo with 162K miles (OBD 1 )

[Todd A Erickson]

It sounds like a AFM (air flow meter) condition to me. Not saying the AFM is bad. Let me explain. When the motor is starting, the most important inputs to the PCM (powertrain control module) is; crank sensor, cam sensor (sets up the “when”), start signal (motor is cranking signal) and the ECT (engine coolant temperature) (how much fuel). After it fires and runs for a couple of seconds and it stabilized, then the PCM looks at the AFM signal. So, if the AFM signal was incorrect, that is when it would bobble and die. My rule of thumb is, if it cranks, fires, short runs then dies, look at the AFM signal or for a unmetered (air that made it into the motor that did not get measured by the AFM) air leak. That leak could be in the breather system. Valve cover breathers, PCV system, intake duct, oil cap. Try this experiment, with the motor idling smooth, remove the oil cap. It will just about kill the engine. That is a unmetered air leak. Any questions?

Todd Erickson
Total Performance Center, Inc.
"Todd the tuner. Can he tune it? Yes he can!!!"
Servicing the Minneapolis MN area.

[Josh Colombo]

As Todd mentioned about the MAF sensor. It actually does sound similar
to an intermittent problem I had. My car would just die, or lose power
when driving. It seemed to be worse during the summer time. It
finally did leave a code. I didn't feel like buying a $300 MAF sensor
if I wasn't 100% sure.

Josh