Left gas cap off, next day engine sputters, service engine soon light



I briefly left my gas cap off after refueling. The gas cap was only off for about 20 minutes while I drove home. Two days later, my car sputtered at start-up and shook. About 2 minutes later, the “service engine soon” light came on.

I’ve done very minor repair work on my car myself (e.g. replacing light bulbs), and I imagine this problem will be way beyond my capabilities. Is there anything I can do before calling the mechanic in the morning?

The gas cap is is pretty new, in good repair, and was replaced about a year ago.

Thanks so much.

2006 BMW 325i
About 92,000 miles

Driving with the gas cap off for 20 minutes should cause no engine performance problems beyond perhaps the check engine light coming on. Unless somebody poured their soda into the tank as a prank. Which seems unlikely. The best approach imo is to have the engine diagnostic codes read using a scan tool. Some auto parts shops will do that for free, no harm to ask. Or you can purchase a scan tool and do it yourself. Once you have that done, if you post the codes here they’re likely be some ideas posted towards a solution pronto.

Hi George,

Thank you. I know leaving the gas cap off for a short time shouldn’t create a problem, but the coincidence is surprising. I will call a mechanic tomorrow morning.

Thanks again.

I don’t know about the sputtering . . .

But at least one of your fault codes will be for evap large leak . . . or maybe even evap gross leak

Hi George,

Thanks so much for your time and good will. After calling 3 mechanics and receiving varying advice, I took the car in today. I have done minor work on my car myself, but after watching the YouTube videos on spark plug replacement, I didn’t think feel confident in my skills or my toolbox. The problem was an ignition coil. There was the question of just replacing 1 or replacing all 6, which I debated, and ultimately chose to replace all 6. The car is 2006 with low miles. I plan to have it for a few more years, and I figure the chances that another ignition coil would go out were high. The labor charge was the same for replacing all 6, though obviously I spent a lot more on the replacement parts. Happy to hear what you would have done.

Thanks again, George and DB for your time and efforts to help out a stranger like me!

Good for you and your shop for getting your BMW purring like a kitten again. Your decision to replace all 6 coils is a good one imo. Sound logic. Best of luck.

Thanks so much, George. I hope you are rewarded with good karma coming your way!

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