Easy Fix -- Hopefully -- For Accidental Cleaning Mistake

Dear Car Talk:

I have a 2014 Toyota Tacoma. I cleaned the mass airflow (MAF) sensor with electronics cleaner and now the truck is running terribly.

A friend of mine said I probably ruined the MAF sensor because I didn't use MAF sensor cleaner. So, I replaced the MAF sensor with one from AutoZone, hoping for a quick fix.

It's still running terribly. I disconnected the hot wire for about 15 minutes, then reconnected it, but no improvement.

I'm not sure what to do next. Can you help me? -- Jeff

I knew I should have shifted some of my IRA money into MAF sensor futures. I'm going to guess that the MAF sensor is not your problem, Jeff. I think you must have done something else by accident when you went in to clean the MAF sensor.

The mass airflow sensor, as the name implies, measures the mass of the air coming into the engine. When air is drawn in, it passes the MAF sensor, which tells the computer how dense the air is, and the computer adjusts the fuel-air ratio accordingly.

Now you've got a brand-new MAF sensor, which is pretty hard to install incorrectly -- you just plug it in. So I'm going to guess that the new MAF sensor is working. Since my only hint is that you sprayed -- I'm guessing here -- a proverbial boatload of electronics cleaner into the air intake in an attempt to clean the original MAF sensor, one possibility is that you managed to foul one or more of your spark plugs with that stuff.

If you fouled a plug or two, the truck would run terribly, even with the MAF sensor working. That's because you'd be running on, say, four cylinders instead of six, which would cause the engine to shake and sound like it's stalling.

An easy way to test if the truck is running on all cylinders is to disable one cylinder at a time -- while the engine is running. So, if you unplug the coil for cylinder number one, for instance, and the engine keeps running exactly the same, that's a pretty good hint that cylinder one was not firing to begin with.

Do that for each cylinder and you'll find out which ones aren't working. Then you can figure out why. You could have bad plugs, bad coils, or you could need a valve job. But start by checking for fouled plugs.

Hopefully you'll find a few and it'll be a cheap, easy fix. Good luck.

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