Diagnostic mystery -> Car randomly dies
02-10-2011, 02:15 PM
#19
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My thinking is that when you say "running" what you mean is "turning over". But that it's not actually combusting. I'm not sure about our 944 DME's, but I know for a fact that my S2000's computer actually shuts off fuel when the RPM is above idle and you are not on the throttle. And you can't feel it because the engine is still turning. I assume most fuel injection systems do this. The point is that I expect that you are mistaking turning over for running, and that if you hit the throttle at that point you'd get nothing.
I'm just trying to clarify. Thoughts?
02-10-2011, 02:50 PM
#20
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Oh Oh, can I chip in my 2C too?
Fuel pressure Damper... pull off the vacuum line and see if fuel comes out! If fuel does come out, change the damper...
DME relay, possible, but not if there is fuel pressure at the rail...
Bad fuel pump, again possible, but not likely if there is fuel at the rail consistently (verify with gauge when no start is present)
AFM, not likely, but hey as long as we are taking the buck shot approach why not?
If the Tachometer needle moves when cranking the DME is getting everything it needs to turn on the fuel pump, and that will verify the reference sensor is working!
next time it won't start, try tapping on the bracket on the rear of the head holding 3 harness connectors (speed/ref sensors and O2 sensor).. or ask someone to try to start the car while tapping on this bracket... the connectors here are prone to corrosion...
Fuel pressure Damper... pull off the vacuum line and see if fuel comes out! If fuel does come out, change the damper...
DME relay, possible, but not if there is fuel pressure at the rail...
Bad fuel pump, again possible, but not likely if there is fuel at the rail consistently (verify with gauge when no start is present)
AFM, not likely, but hey as long as we are taking the buck shot approach why not?
If the Tachometer needle moves when cranking the DME is getting everything it needs to turn on the fuel pump, and that will verify the reference sensor is working!
next time it won't start, try tapping on the bracket on the rear of the head holding 3 harness connectors (speed/ref sensors and O2 sensor).. or ask someone to try to start the car while tapping on this bracket... the connectors here are prone to corrosion...
02-11-2011, 01:14 AM
#21
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Hi,
sorry, I didn't mean AFM spring tension, I meant he dialed in the AFM using the adjustment screw. He also adjusted the idle. Didn't really correct the problem with it spontaneously dying.
I'll try changing the DME relay.
Tuned up the car not too long ago, spark plugs, cap, rotor, wires, fuel and air filters all within the last two years.
sorry, I didn't mean AFM spring tension, I meant he dialed in the AFM using the adjustment screw. He also adjusted the idle. Didn't really correct the problem with it spontaneously dying.
I'll try changing the DME relay.
Tuned up the car not too long ago, spark plugs, cap, rotor, wires, fuel and air filters all within the last two years.
02-11-2011, 01:17 AM
#22
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Update:
So I was messing with the AFM, and thought that maybe it needed to be refurbished. Pulled off the cover, and retracked the metal springs. When I put the AFM back in and tried to start the car, similar problem as before, no start, except now it would catch if I cranked it and floored it. I can get the car going for a little bit, and it'll continue to run as long as my foot is on the gas, but as soon as I let off, it'll drop down past idle and die.
Does this mean its my AFM thats FUBAR? Or did I just create another problem @_@
So I was messing with the AFM, and thought that maybe it needed to be refurbished. Pulled off the cover, and retracked the metal springs. When I put the AFM back in and tried to start the car, similar problem as before, no start, except now it would catch if I cranked it and floored it. I can get the car going for a little bit, and it'll continue to run as long as my foot is on the gas, but as soon as I let off, it'll drop down past idle and die.
Does this mean its my AFM thats FUBAR? Or did I just create another problem @_@
02-28-2011, 12:57 AM
#24
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Hey all,
thanks for the helpful advice.
Disconnected the AFM, and suddenly car ran normal again.
I think I buggered the AFM when I was cleaning it.
However, the car will run for a few minutes, and then suddenly die.
It'll turn over, but won't start. If I wait about a minute or so, I can get it started and going again, and it'll run for a minute or two, but then die again. Sounds/feels like its suddenly losing fuel pressure.
How do I get to the fuel distributor in these cars? Do our cars have one?
thanks for the helpful advice.
Disconnected the AFM, and suddenly car ran normal again.
I think I buggered the AFM when I was cleaning it.
However, the car will run for a few minutes, and then suddenly die.
It'll turn over, but won't start. If I wait about a minute or so, I can get it started and going again, and it'll run for a minute or two, but then die again. Sounds/feels like its suddenly losing fuel pressure.
How do I get to the fuel distributor in these cars? Do our cars have one?
02-28-2011, 05:24 AM
#25
I would start by checking the fuel pressure. Help can be found here.
http://www.clarks-garage.com/pdf-manual/fuel-01.pdf
http://www.clarks-garage.com/pdf-manual/fuel-01.pdf
http://www.clarks-garage.com
