Questions and Answers
Intrepid Has Some Strangeness
Q. Hello Vincent, I have a 1995 Dodge Intrepid. It has a 3.5 liter engine, P/S, ABS, A/C, rack and pinion, and 83,000 miles on the engine.
I just had the transmission replaced at 82,000 miles, but the problems I'm having were occurring before that. There are three areas I'm having problems and no one around here can seem to find what the solutions would be.
The engine is sporadic about it's idle speed. One moment it will idle at about 600 RPM, at the next stop light it might be idling at 1000 RPM, or 800 RPM. It doesn't matter if the A/C is on or not.
The A/C sometimes will work, just about freeze you out of the car and then one mile down the road the air coming out of the vents will be the temperature outside. The compressor comes and goes. It doesn't have automatic temperature control. I had this checked, but the technician only found it was very slightly (much less than one pound) low on refrigerant.
The last problem is with the instrument cluster. Sometimes the speedometer, odometer, tachometer all work together as they should. Other times the tach will work, but no speedometer or odometer, then still other times none of them will be working. It is just as likely to happen one time as another.
I try to take good care of my car and get things repaired as they happen, but these problems have everyone I know stumped. Any ideas?
Thanks for your time,
JerryA. The Idle speed is controlled by the Powertrain Control Module (PCM) and calculates the proper idle speed for conditions. The PCM calculates proper idle speed using information from throttle position, vehicle speed, and coolant temperature sensors and brake, and neutral/safety switches. It then sends a signal to the Idle Air Control (IAC) motor. The IAC motor controls air flow through a passage connected to both intake manifold plenums. The PCM controls engine idle speed by adjusting the IAC motor to compensate for engine load or ambient conditions. I would guess the problem is in the IAC itself. They can get gummed up and lose calibration. It can be tested with a scan tool to determine if it is operating correctly. Another likely cause is the coolant temperature sensor.
The A/C problem could be a bad Body Control Module (BCM) or Evaporator Temperature Sensor (ETS). The evaporator probe is a temperature sensing element located at the coldest point on the face of the evaporator. The evaporator temperature sensor prevents condensate water on the evaporator core from freezing and obstructing A/C system air flow. Output from the probe is sampled by the BCM. It is used to switch the A/C compressor clutch off before evaporator freeze up occurs. The clutch is switched off when the probe reaches 33.7 degrees. It is allowed to switch on when the probe temperature reaches 35.7degrees. Either one of these could be the cause of the A?C problem. The problem is worsened when the recirc or Max mode is on.
The speedometer receives its information from the BCM. Information on vehicle speed is transmitted from the PCM to the BCM. The PCM receives its information on vehicle speed from the Transmission Control Module (TCM). The BCM calculates the position of the speedometer pointer based on the input from the PCM and adjusts the position of the gauge pointer as necessary.
The tachometer receives its information from the BCM as well. (Methinks I dedect a pattern here.) Information on engine RPM is transmitted from the PCM to the BCM. The BCM calculates the position of the tachometer pointer based on the input from the PCM and adjusts the position of the gauge pointer to the necessary position.
So, from what you describe the A/C and speedometer problems could be related and are in the BCM itself or possibly a loose connector or ground wires. If we wanted to find the connection all three problems have, then we have to take a hard look at the PCM, it's connectors and grounds.
Additional Information provided courtesy of ALLDATA
