Q: Rough idle speed in cold weather and no heat in cab

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In cold weather the truck has a very rough idle, sticking around 500 rpms and occasionally dropping below 500 abruptly and on occasion stalling. This only happens in idle. The other issue is that when I turn the heat on in the cab i get a short burst o warm air then just air, no heat.

My car has 192000 miles.
My car has an automatic transmission.

When the engine is cold, the engine coolant temperature sensor must be working properly to signal the PCM to enrich the mixture on cold start. If there is a fault with that sensor, you can experience rough idle idle as you are describing. Other possible causes of rough idle are uneven cylinder compression, a vacuum leak, an air induction fault like a stuck idle air control valve or a faulty throttle position sensor, problems with the mass air flow sensor, defective spark plugs, a weak coil and defective oxygen sensor(s). If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a rough idle diagnostic and the responding certified mechanic will get this resolved for you.


With regard to the no cabin heat issue, common causes of no cabin heat include malfunctioning blend door(s) (part of the in-dash ventilation network), a faulty or stuck heater control valve, a plugged heater core, stuck open engine cooling thermostat, collapsed hoses, and low coolant level. The cost to resolve the problem depends on which of the foregoing faults is the cause. If you desire a diagnostic to determine exactly why there is no cabin heat, please request a non functioning cabin heater diagnostic and the responding mechanic will come right to your location and get this resolved for you promptly. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.

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