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Q: Hard to start when engine is cold

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It had a code p0403 Egr issue. I replaced the egr valve and transducer but it didn't fix it. Sometimes it will start right up other times, it turns over great and tries to start then when I open the throttle it will finally start. It runs rough until it starts warming up then it smoothes out and if I shut it off it will start right back up if the engine is warm and runs great. I also have a code that shows o2 sensor bank 1 sensor 1 is shorted but I have not changed it yet. It feels like it lacks power so I believe the catalytic converter is bad. A temperature measurement on the inlet side shows 550 degrees and on the outlet side is 500 degrees. because of the rough idle issue when it is cold I recently cleaned the throttle with brake cleaner sprayed on a rag and sprayed the maf sensor with an aerosol electronics cleaner. Thanks...

My car has 150000 miles.
My car has an automatic transmission.

Hi there. It is possible that the O2 sensors are causing the hard starting problem. It’s also very common for a cold start injector or the radiator coolant temperature sensor to cause cold weather starting problems as well. I would check those components for operation and connectivity and replace if needed. If you still can’t find the source of your cold starting issue, contact a professional mobile mechanic to complete a car is hard to start inspection.

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