Q: Rough idle on cold starts

asked by on February 16, 2017

Im having rough idle on cold starts for 5 to 10 seconds then back to normal. Have not changed spark plugs since i bought it last February. They say it might be a slight leak from head gasket. No overheating and bubbles in radiator. No steady white smoke. No error codes. Just the slight smell of burnt gas from exhaust. No change in power either. What could be the problem.

My car has 195000 miles.
My car has a manual 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 possibilities are a vacuum leak, an air induction fault like a stuck idle air control valve, problems with the mass air flow sensor, defective spark plugs and possibly a weak coil. 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. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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