Mark Doiron

Ran a can through a tank of gas the past several weeks (I don't drive much unless on a road trip). No change in problem. Will try foam into air intake next.

Mark Doiron

Finally ran the Seafoam through the intake. Doesn't seem to have helped with the tapping noise.

Machoo

Bummer!

Mark Doiron

More info: Visited a professional mechanic who is a friend of mine. He poked around with a stethoscope and came to the same conclusion as me: I have a noisy fuel injector. I told him I'd used SeaFoam and he suggested before changing the fuel injector (actually all of them since I'm at 200K miles on the motor) that I should try two cans of Royal Purple Fuel Injector Cleaner--using it at a strong dilution (don't fill gas tank completely after adding). So I'll be doing that. I don't expect it to solve the problem, but will advise here if it does.

BTW: Skulking around YouTube videos I found several from folks who had a very similar sound (on different vehicles) and ended up changing a fuel injector to repair. It's funny because there are dozens of folks commenting that a fuel injector would never be that loud, yet the video poster specifically says that replacing the fuel injector fixed the problem. It's a really annoying noise that is easily confused with a bad lifter or other, much more serious problem. And, yes, fuel injectors can be that loud.

Oh, one last tidbit: He strongly suggested suck up the cost and use OEM fuel injectors. He's seen too many inconsistent quality problems with aftermarket.

RageQuit4913

I work in the watercraft industry and fuel injectors are a common replacement. Since we have a winter storage season in my area the fuel sits and gunks up. Running cheap fuel makes that worse even during usage. And just as worse as low grade fuel is the ethanol in it that breaks down way too fast. Injectors can make no noise all the way to a heavy tapping sound.