2002 Dodge Ram Fast idle?

2002 DODGE RAM
198,000 MILES • V8 • 4WD • AUTOMATIC
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SEPTJULY@TELUS.NET
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We live in a cold climate. When the temp. drops below -10c and we start the truck in the a.m. (even if it has been plugged in) most of the time (not always) after about 1 minute it will start fast idiling and blue smoke will come out of the exhaust and what smell like raw diesel. When we turn it off and restart it it will sometime not start "banging hard" idle.
We had the fast idle replaced a couple of years ago and now the mechanics cannot find out what is wrong with it. We can't even park it close to the house, we will get gassed out!! Once it is warmed up and started again it is fine. I do have video of it changing from regular to fast idle.
Dec 7, 2009 at 12:35 PM
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CARADIODOC
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"Fast idle" is a symptom, not a thing that can be replaced. Could you be referring to the Automatic Idle Speed (AIS) motor being replaced a couple of years ago?

The raw fuel smell suggests a sensor problem, most commonly the MAP sensor. It reads engine vacuum to determine load on the engine. More load requires more fuel. There are two different possibilities with this type of sensor. At first it can report incorrect readings that are within the limits of normal operation. The engine computer will believe the sensor and command extra fuel to be delivered. Second, when the sensor gets worse and reports readings that are outside specific design limits, the engine computer will know that sensor can not be trusted. It will disregard the sensor, inject an approximate, calculated value based on other criteria, memorize a diagnostic fault code in the engine computer, and the computer will turn on the "Check Engine" light to let you know an emissions-related problem has been detected. Due to that injected, calculated value, it's not unheard of for the engine to actually run rather well, but the clue is the Check Engine is on.

If your Check Engine light is on, there is a diagnostic fault code that will lead you to the circuit with the problem. Do not disconnect the battery until the code(s) has been recorded or that valuable information will be lost.

caradiodoc
Dec 8, 2009 at 2:56 AM