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Replaced Coolant Temp Sensor -- Fixed Cold Idle Problem 200 1983

posted by  toofourdy on  Tue Oct 12 04:03 CST 2004
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I had a serious problem with 245 inasmuch as, after I started it in the morning, it would die. Then, once it started, it idled fairly erratically and would die if I attempted to drive it before it warmed. This weekend, I pulled the intake manifold and replaced the manifold gasket and also replaced the coolant temperature sensor (while I was at it, I replaced the oil breather box and heater hoses). Now, it starts right up and idles fine. Just a thought for those of you who have had similar problems.








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    Replaced Coolant Temp Sensor -- Fixed Cold Idle Problem 200 1983

    posted by  1984GL on  Tue Oct 12 19:21 CST 2004
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    last visit: Fri Apr 26 17:07 CST 2013
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    Also, I've seen the connector on the coolant sensor corrode and cause a rich condition. Remember, an open sensor causes a rich condition. So when a coolant sensor corrodes and causes an open coolant sensor circut, the ecu is seeing a cold engine, even when warmed up. You can spray brake cleaner through the intake to clean it up, but its better to remove the intake and replace the sensor and clean the connector.








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    Replaced Coolant Temp Sensor -- Fixed Cold Idle Problem 200 1983

    posted by  someone claiming to be Ursula on  Tue Oct 12 06:42 CST 2004 [RELATED]

    I have a similar problem, although sporadic. Prior to changing the coolant temperature sensor, did you experience any overheating or indication of running slight warm (or cold)? The sensor in my 740 is probably 17 years old (1986) and I've cleaned my IAC valve and done a minor tuneup, and during warm summer weather idle was fine, but now that it's getting cooler in the mornings, morning idle is kinda rough for about 4 or so minutes until the engine temperature starts climbing to normal range.








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      Replaced Coolant Temp Sensor -- Fixed Cold Idle Problem 200 1983

      posted by  B.C. on  Tue Oct 12 10:13 CST 2004
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      last visit: Wed Mar 28 22:28 CST 2012
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      I believe that the coolant temp sender that twofourdy replaced is the one that "talks" to the engine control unit, not the dash gauge.

      When that ECT goes bad - maybe due to old age - the ECU thinks the engine is conld and needs more fuel, even after the engine is fully warmed up. Thus it gets a too-rich mixture and the o2 sensor tries to control back, but cannot enough.

      Failure of the ECT is not tied to engine over-heating, and gives no dash indication.

      good Luck,

      Bob

      :>)







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      Replaced Coolant Temp Sensor -- Fixed Cold Idle Problem 200 1983

      posted by  toofourdy on  Tue Oct 12 07:12 CST 2004
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      I hadn't noticed any temp problems such as overheating. I just had the exact same problem you are describing. The car did not do this last fall, so I suspected something was amiss.

      FCP Groton sells the sensors. Replacing the sensor is a snap, just unplug the connector and unscrew it. Getting too it is the only (albeit only slightly) hard part as I had to remove the intake manifold. I also drained the radiator before I did it. Otherwise, you might have to fight radiator fluid getting it back in. Good time to flush your system.

      I am still not convinced 80s model Volvos idled properly coming off the showroom floor. I love my Brick but I've never seen cars with such systemic (or is it endemic?) idling problems.







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