Our 2001 3.2TL will misfire (characteristic bucking, and sometimes it's enough to flash the engine light) if it revs too high on the highway. Forcing an upshift will cause the misfiring to go away. It mainly happens on uphill grades. Our mechanic can't find a root cause. Any ideas? Ignition system? VTEC? Cylinder deactivation? Could it even be the fuel? (Disclaimer: We put regular in it because while, in typical luxury car fashion, premium is recommended, the manual says it is not required, and the worst regular should do is produce occasional knocking, and not heavy misfiring like is happening here).

 

That's not how I read my owners manual. (emphasis added)

"Your Acura is designed to operate on premium unleaded gasoline with a pump octane number of 91 or higher. Use of a lower octane gasoline can cause occasional, metallic knocking noises in the engine and will result in decreased engine performance."

Put some premium in it (yes I know it's expensive). and pull the codes to see if there are any pending.

 

TBH, that looks like the cheapest thing to try first. However, since it's heavy and feels like misfiring, I'm dubious. Very well could be a bad knock sensor, though, as far as I can tell.

 

Update: It's the ignition system, specifically the spark plugs. It's not a good idea to cheapen out on them, right?

 

Correctamundo. Many swear by NGK, can be found on rockauto or amazon occasionally has them for less.

 

So...now that I've driven the car with new spark plugs, it was very clearly overdue for new ones. I need to get used to having all the power again!

 

OK, it's confirmed fixed after I took it on the highway

 

A good highway run helps to clean things out a bit too.