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Old 10-26-2007, 09:07 AM   #1
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1994 Cougar


V6 92K Auto.

Inherited when in-law passed away. Was a proverbial "little old lady from Pasadena" vehicle, driven infrequently.

When first started from cold, car runs extremely rough, almost like it's missing a cylinder or two. Revving motor to 3K keeps it going. After about a minute at 3K, car settles down and runs smoothly.

Any ideas?

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Old 10-26-2007, 10:14 AM   #2
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1994 Cougar


Does this only misfire just at cold starts or all starts, but just not as bad. Most early CC cars computer stores hard and intermittent faults, only the hard faults will turn on the MIL lamp. I would have the car scanned for any intermittent codes. In my experience, most intermittent early Ford problems are caused by wiring or terminal connections. I would also have the fuel pressure checked when cold.
Early Fords are difficult to diagnose without the proper test equipment (break out box) and there is no way to view the data stream real-time.
I would check the two bulk head connector terminals (40 or 60 pin?), by the master cylinder for corrosion. Be careful about spreading open female terminals, you will create another intermittent problem.
If you want to throw parts at it I would try an engine coolant temp sensor and an inlet air temp sensor.

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Old 10-26-2007, 10:37 AM   #3
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The problem only happens on cold starts. Once the engine is warm, restarts are smooth.

Does that change the picture at all?
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Old 10-26-2007, 10:59 AM   #4
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On your next cold start, turn the ignition key to the run position do not crank the engine. You should hear the fuel pump run for 15-30 seconds, humming noise from fuel tank. When the hum stops, turn the key off wait 5 seconds. Repeat two to three times. This will prime the fuel system. If the car starts and runs fine, you have a bad fuel pump check valve. You can either replace the pump or live with it.
You could measure the resistance of the ECT when cold with a DVOM and compare to Ford specs. Off hand, I don't know what it should be, but it should be quite high (50k+ ohms). The hardest part will be hooking up your meter leads. It could be located on a cylinder head or the intake in a coolant passage area. It will have a two wire connector going to it.
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Old 10-26-2007, 11:52 AM   #5
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Great stuff...I'll try it and let you know.
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Old 12-29-2007, 02:05 PM   #6
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Your trick worked. It seems to be the fuel pump check valve.

I'm not sure I want to mess with the removing the fuel tank, so it might be best just to live with it.

Thanks for your help.

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