QuestionV6. When it is cold outside, car hard to start. Does not want to idle when started until warm... replaced Idle control valve and throdle pos. sensor. Could it be the map sensor? Or what? Runs good when warm and drives good, just hard to start when cold...
AnswerHi Scott,
On these newer cars, the coolant temp sensor replaces the choke. If that is sending faulty signals to the computer, the car will not work well, until warm (closed loop). In closed loop the O2 sensor is in control and can adjust for a wrong coolant reading. You may also be noticing bad fuel economy.
Map sensor could cause problems, but if it runs good after warmed up, I would say it is working correctly.
Do you have a check engine light? Did you try to pull codes? With key on and engine off, use a paper clip and jump across A and B terminal in the 12 pin connector under your dash. This is rectangle and black. Count the blinks on the check engine light. The code is two digit. So Two blinks-short pause-5 blinks - long pause, is a code 25. Get a repair manual to help identify these if you don't know what I mean. You can get a repair manual from the library. There may also be info online.
The coolant level may be low. If so, the coolant temp sensor cannot read the temperature. Top this off. Check the map sensor vacuum line for cracks.
May also have a vacuum leak causing too lean condition until the O2 takes over. Once it is idling, spray water around the vacuum lines and intake gasket, to see if you can get the engine to stumble.
Hope this helps.
C J S
