Narrative:

The crew and I had been flying aircraft X earlier that day on a previous turn and this was our second turn. Before we pushed back from the gate; maintenance came aboard to get the logbook as they conducted a service check. We were able to close up the door and push back on time with no issues. Once we pushed back; we started both engines and shutdown the APU with no issues. Once we received our taxi instructions; I moved the throttles up to move the aircraft. Within about 10-20 seconds of the throttle movement; a sudden and strong odor permeated the cockpit. It was an incredibly strong odor and it kept getting stronger. I would describe the smell as a metallic and burnt oil type smell. No visible fumes were present. I decided to stop the aircraft and check with the first officer to see if they smelt it as well. They agreed that it was very strong. I then called the flight attendants to see if they smelt it. Flight attendant-a said they had a faint smell; but nothing strong; and flight attendant -B stated they didn't smell it. I decided to open up the windows in an attempt to get some fresh air to determine if perhaps the smell was just a brief instance. I instructed the first officer to tell ground that we would need to hold for the time being while we sorted out the issue. After a short time; I opened the vents and smelled [it] again. I had my oxygen mask ready; but felt that at that point it inhibited communication more than anything. The first officer and I instead chose to keep the windows open and vents closed. I made several calls to the company to coordinate with dispatch and maintenance in regards to the situation and a gate return. After a short time the first officer and I agreed the flight could not be conducted safely and chose to do a gate return. We called operations to get a gate and after about 20-30 minutes we were able to taxi into the new gate and deplane the passengers.

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Original NASA ASRS Text

Title: EMB-175 Captain reported a metallic odor during taxi which resulted in a return to gate.

Narrative: The crew and I had been flying Aircraft X earlier that day on a previous turn and this was our second turn. Before we pushed back from the gate; Maintenance came aboard to get the logbook as they conducted a service check. We were able to close up the door and push back on time with no issues. Once we pushed back; we started both engines and shutdown the APU with no issues. Once we received our taxi instructions; I moved the throttles up to move the aircraft. Within about 10-20 seconds of the throttle movement; a sudden and strong odor permeated the cockpit. It was an incredibly strong odor and it kept getting stronger. I would describe the smell as a metallic and burnt oil type smell. No visible fumes were present. I decided to stop the aircraft and check with the First Officer to see if they smelt it as well. They agreed that it was very strong. I then called the flight attendants to see if they smelt it. Flight Attendant-A said they had a faint smell; but nothing strong; and Flight Attendant -B stated they didn't smell it. I decided to open up the windows in an attempt to get some fresh air to determine if perhaps the smell was just a brief instance. I instructed the First Officer to tell Ground that we would need to hold for the time being while we sorted out the issue. After a short time; I opened the vents and smelled [it] again. I had my oxygen mask ready; but felt that at that point it inhibited communication more than anything. The First Officer and I instead chose to keep the windows open and vents closed. I made several calls to the Company to coordinate with Dispatch and Maintenance in regards to the situation and a gate return. After a short time the First Officer and I agreed the flight could not be conducted safely and chose to do a gate return. We called operations to get a gate and after about 20-30 minutes we were able to taxi into the new gate and deplane the passengers.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.