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Tim West
Tim West, ASE Certified Technician
Category: Car
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Experience:  ASE Certified Service Manager for Bridgstone/ Firestone
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Idle..about 800 RPMs for approximately 3 to 5 seconds, then die

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I own a 1983 944. I can start it. It'll idle at about 800 RPM's for approximately 3 to 5 seconds, then die. It'll do that all day long, if I kept at it. I've changed the fuel pump, filter, and installed a new fuel pump relay. I've been told it might possibly be the Mass Air Flow Sensor.
Submitted: 5 years ago.
Category: Car
Expert:  Tim West replied 5 years ago.
Unplug the mass air flow sensor and recheck the problem.
Customer: replied 5 years ago.
Where is the M.A.F.S.?
Expert:  Tim West replied 5 years ago.
The mass air flow sensor is located between the air filter box and the throttle. On the hose.
Tim West, ASE Certified Technician
Category: Car
Satisfied Customers: 4638
Experience: ASE Certified Service Manager for Bridgstone/ Firestone
Tim West and 13 other Car Specialists are ready to help you
Customer: replied 5 years ago.
That didn't work.
Expert:  Tim West replied 5 years ago.
No probelm let's look into some more. I will be right back. Let's check for vacuum leaks.

1. You will need starting fluid for this.. Check all over for any vacuum or false air leaks or crankcase ventilation leaks. Try spraying starting fluid into the throttle while cranking to see if the vehicle starts. Get back to me on this I would like to identify if it's a spark or fuel issue.

If you have tools and a good knowledge of cars:

2. At Digital Motor Electronics control module (DME) test the power feeds and grounds. Pin 16,17 and 5 (Brown wires) should be constant ground. Pins 18 and 35 (Red/Yellow) should be battery voltage (B+) with key switched on from DME relay.

3. Verify ignition reference pulse at pin 1 Green wire with engine cranking or running, it should be a pulsed signal. The dwell angle will vary depending on electronic control unit control function.

4. Verify start signal to DME on pin 4 Red/Black wire, B+ in crank position. There should be continuity to ground when not in start position, through the solenoid winding of starter.

5. If all ok, test the injector pulse width at the injectors with a meter or scope. Typical injector pulse width for this engine will be approximately 2.5 to 4.5 milliseconds at hot idle. If out of this range, test input signals to the DME from sensors. If all sensor inputs are correct but the DME outputs are incorrect, the DME may be faulty.

Edited by Tim West on 10/6/2009 at 8:57 PM EST
Customer: replied 5 years ago.
My car starts, that's no problem. It just doesn't stay running. I don't have anybody available to crank the engine while I spray the starting fluid. I'm a mechanic at a packaging company. My experience with cars is limited due to lack of diagnostic equipment. Before computers, I had no problems fixing anything. I've done lots of repairs to my Porsche, but this problem has got me stumped. I've had lots of older cars, Fairlanes, I built a Falcon hot rod, two souped up Mustangs, and a Harley chopper. Working on them, no problem. I thought maybe my problem with the 944 might be the computer. I've had the car since 1991. It's been a good car. 2007 I got cancer, this problem occurred. I'm healed now, and want to get this problem resolved. Doing steps 2-5 is out my scope of profiency. So I'll probably end up taking the car to an aquaintenance who has a shop that specializes in this sort of thing. I was hoping to be avoid that since the cancer fiscally wiped me out. Thanks for trying to help anyway.
Expert:  Tim West replied 5 years ago.
Well try spraying some fluid in the throttle and then cranking. See if that starts her.
Customer: replied 5 years ago.

Hi Tim, sorry I haven't gotten right back to you. I was very busy. I sprayed starting fluid and my car runs as long as the fluid lasts.

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Tim West
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ASE Certified Service Manager for Bridgstone/ Firestone