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Avalon running rough

my husband noticed our avalon is running ‘rough’. this usually happens after driving the car over an hour or more. we took it to the toyota dealer last week and they couldn’t find anything wrong. we’re planning on driving this car in april on a trip from minnesota to the east coast (north carolina).



the mechanic did say the spark plugs are not the right ones for this car (they’ve been in for 2 years or so).







Well, things like that are very often just a matter of the basics - spark plugs and wires, fuel and air filters. So did you get a correct set of spark plugs installed or what? How old are those wires?

Someone ought to test the rest of the ignition system - especially when the components get hot.

Is the check engine light on?

Unless you need warranty or recall service you don’t need to use a dealer.

As cigroller stated, start with the basics.
A good beginning would be to have the correct spark plugs installed and then see if the symptoms change.

thank you very much for the reply.
we’ll replace the spark plugs and check the wires. the check engine light only comes on before starting the car (after clicking on the key)

the check engine light does not come on when the engine runs rough. The spark plugs are about 3 yrs old and are single point, not double like they should be. One mechanic mentioned possibly a sticking EGR valve, another thought possible fuel injectors. The guy at the auto parts store thought single vs double spark plugs wasn?t significant, for what that?s worth.