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Hi, All,

New to the list, thanks for being there!

I have a 1994 Taurus GL w/ 3.0l FF motor...

Odd problem hoping someone has heard of it. I don't have the necessary device to read diagnostic engine codes (probably should invest) so I am doing this by the seat of my pants.

I have a problem with what can be desrcribed as "temperature spikes", but there is more to it than that.

I have thoroughly flushed the system, and replaced the thermostat, which helped; the spikes don't go as high as they used to, but they are still there. I have also confirmed that flow through the system is fine. The water pump has a mild squeak, but it isn't leaking yet, and since the temperature goes up and down, I don't suspect the water pump.

Whether or not the A/C is on, it does not change the "apparent" (I put that in quotes, since the gauge itself does not have actual degrees) range of the spike. I don't know if this means anything without looking at the gauge itself, but the temperate will jump in a matter of a few seconds to above the "A" in "Normal", and then drop between the "N" and the "O". However, when the A/C IS on, I can get some knock/ping. The electric fan, both before and after the flush/thermostat change consistently turns on at about the "M" (this is silly), and remains on until the temperature drops again below it. Ambient air temperature does not seem to matter.

There are two temperature sensors on this engine; one feeds data to the PCM(and presumably turns the fan on and off), the other controls the gauge (the former is located in the top of the intake manifold, the latter in the #1 heater hose connection, near the thermostat housing). If the latter also controls the fan, then I would suspect the sending unit going to the PCM; but if my assumption is correct, that the former controls everything but the gauge, I have a hard time suspecting either, since the fan comes on constently in relation to the gauge.

The knock/ping when the A/C is on also confuses me, since the engine has an anti-knock sensor.

Also, on occasion, the transmission will jump in and out of gear at higher temperatures. At some point, the cooling system is no longer seemingly able to bring the temperature back down all the way (although it never leaves the normal range), and the transmission starts to jump out of gear. Releasing the throttle and re-depressing it corrects, until it happens again of course.

My instincts tell me that these problems are related, and the root of the issue is the PCM. However, due to the expense of the PCM, I wanted to get some opinions from folks whom have dealt with the Sore-ass before, possibly saving me a bundle. This is a very strange set of issues!

Thank you very much for your responses, I know this is rather long, but I wanted to be sure to give you guys all the info I possibly could.

HS Brown
 

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check your thermostat, mine fluctuated up and down all the time, if you put a stant replacement in there without an air bleed hole that will do it. Make sure its at least 50/50 mix of coolant. The cooling fan relay was also a common problem of failing or wearing out.

as for your tranny, that happened to me too, but if its slipping out of gear, shuttering, not shifting smoothly period, junk the car, your forward clutch piston and/or the seals are going in your tranny. Mine is starting to show signs of its last leg at 120k.
 

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P.S. They arent starnge issues, i've already gone through them all your describing exactly! I'm hoping to ditch the car in the next few months, its getting too expensive to fix.
 

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NESHO SCT Tuner
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Sounds like air in the system. A good sound cooling system will rid it self of any air. If there is a slight leak at the radiator side tanks when cold or a bad radiator cap though it will not purge the air out.
 
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