Inconsistent engine performance

[1gasenvy1]

Over the last 2 month I have experienced inconsistent engine performance from my '99 banger. On any given day it will our like a kitten, cruising down the hwy at 65mpg and sound like a million bucks. On another day it seems that it's running a little rough, not bad, but enough to notice. I've tracked the days and type of weather and it doesn't seem like it's an atomospheric thing, thin air .vs thick air, damp .vs dry etc. This bad boy has 187k and keeps running and running like the energizer bunny. Any Ideas out there?

Gasenvy.

p.s. How about those Pruis problems, First the gas peddle, then now the brakes. Can't wait for the big Battery problem, replacement cost $8000+.

[Crvett69]

when was last time it had a tune up? i would check the plugs and air cleaner and replace the wires if they have been on car a while and put a can of injector cleaner in the tank

[Woodie83]

Get a compression test. At 187K miles it almost certainly needs valves.

[Crvett69]

if it was valves it would be consistently bad, not good one day, bad the next then back to good. it also possible your EGR valve is sticking