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Join Date: May 1999
Location: Salt Lake City, Utah
Posts: 4
d-jet question


I have a 76 with a 2.0. I need to know how to test the temp. sensor in the throttle plentum. Also is this the sensor that controls the cold-start valve? (my engine is running extremely rich, but when I unplug the temp. sensor, it clears up and runs much better) I have swapped pressure sensors, I have a new head temp. sensor, new trigger contacts. I have swapped the cpu and stiil very rich. The only thing that makes a difference is disconnecting the temp. sensor in the throttle plentum. any sugestions would help. Thank you
Old 05-19-1999, 09:46 AM
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On a 2.0, the intake air temp sensor sticks straight up out of the plenum, I think in the left-front corner. It is an NTC thermistor, much like the head temp sensor. When it is cooler, it has more resistance, and makes the FI inject more fuel. The FI interprets an open circuit as infinite resistance, and infinitely cold. So, when it's unplugged, the FI injects more fuel than when it's plugged in.

If your car runs better with it unplugged, you may be running too lean. Or your ignition may be out-of-whack. My car ran better with a VERY rich mixture than with a "normal" one when the points were pitted.

The thermo-time switch controls the cold start valve. On a 74, it is horizontal (not up and down like the intake air temp sensor). I know the 75-76 TTS is different (two wires vs. one for the earlier ones) but not sure if the mounting changed. I don't think it did, but... Anyway, the mounting is down below the plenum, on a bracket sticking down and then to the side from it.

If in doubt, unplug the cold start valve--left-rear corner of the plenum. Then the TTS has no effect.

But I strongly suggest checking the ignition system first.

--DD
Old 05-19-1999, 11:38 AM
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Old 05-19-1999, 11:38 AM
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