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Re: 1986 4CSQ problem

>Three days ago it got much worse. The gas mileage is the same - 14-16 MPG,
>but the hesitation is much more pronounced and happens all the time. I can
>drive the car, but I have to be very careful when starting from a stop or
>if I try to pass someone. Just because I press on the gas, it doesn't mean
>the car will get going. (Although once I'm at the speed I need to go, I
>have no trouble holding it.)
>Here's an odd thing. When the car is stone cold, everything's fine. After
>about 5 minutes or so it goes to pot. :( 

Check the resistance of the cold-running temp sensor.  It should be >2K
ohms when cold, under 500 ohms when warm.  If this has failed so that
it always reads cold (or if the connector has gotten corroded), then
the engine will be running very rich.  This is exactly what you want
when the engine is cold, but not good for the engine when it warms up.

The sensor is located on the underside of the upper coolant flange on
the head (the cold-start thermoswitch is on the top of this same flange).
An easy way to check the sensor operation is to warm the engine up, shut
the engine off, pull the connector, and short the two leads together with 
a wire.  This simulates the response of the temperature switch when the
engine is nice and hot.  Restart the engine, and if it runs smoothly
again, then either the sensor or the connector/wiring is the problem.
Connecting a multimeter to the leads of the temp sensor itself should
tell you if it it dead, also.

'85 Coupe GT
Eric J. Fluhr                                Email:  ejfluhr@austin.ibm.com
630FP Logic/Circuit Design                   Phone:  (512) 838-7589
IBM Microelectronics Div.                    Austin, TX