2004 Matrix runs like crap

[syrgrad91]

So my wife has a 2004 Matrix (the standard model) with 87k (miles) on the odometer. For the past few months it's been running like crap, not much power on the freeway and knocks at idle. When I have her run the occasional tank of 91 octane Chevron it runs better, not perfect, but better (plus better gas mileage to boot). I occasionally have her run some sort of fuel system treatment (Seafoam, Lucas) but that hasn't helped much. Before I start swapping parts is there anything that's obvious that I should be looking at?

[mikered30]

http://matrixowners.com/?showtopic=65513

Check out cleaning the TB and MAF.

[dorman68]

Your knock at idle is most likely your belt tensioner. Toyota issued a service bulletin addressing this issue which involves replacing the belt tensioner with an updated part. I would run the engine without the belt to see if the knock goes away, if the knock goes away with the belt off then the tensioner is the problem.

****don't run the engine for more than a minute without the belt as the water pump isn't rotating and could cause the engine to overheat.

[mistamatrix]

Start w/ the cheap remedies first!

[trboboost91]

when is the last time it got a fresh set of TOYOTA plugs.

[anita]

all you need is a tune up and Daddy said never put anything in it but Shell gasoline