I have another thread in this forum if anyone cares enough to get caught up just called "Help Diagnose My Daily Driver".

Cliff Notes:
00 Toyota Corolla
105k, automatic
Getting crappy gas mileage, hesitating a little from time to time, and a little valve chatter.

Changed the oil, put Seafoam in the gas tank (didn't do the other stuff yet cause I'm not entirely sure where it goes), changed the spark plugs to iridium.

UPDATE: Filled up 2 days ago, got 27mpg, still not where it should be. The valve chatter seems to be gone, so I guess the spark plugs did the trick there. Seems to really suck especially hard at gas mileage on the highway, which is backwards to me. Also, still has it's brief moments of hesitation. Still no CEL. What next?

O2 sensors and fuel filter?

 

Are you sure? EPA rates this car at 25/34 and 28 comb. 27 is right there. Its hard to go by mpg because there is a lot that goes into that number - temp, driving style, a/c, gas, weight of car, etc. http://www.fueleconomy.gov/feg/findacar.htm

Is this a model that the valve lash needs to be corrected every so often? Back when I was out east a co-worker of mine had an older Coro (mid 80s). We had to adjust everything.

Is the cat-convert org? If so those get clogged over time.

I would check the fuel filter and pump. 02s couldnt hurt.

There is also this IV bag sort of fuel system fogger. I get mine done through my shop here (doubt its in stores). But it fogs and cleans the inj. system - makes a noticable diff. in my Evo (I do this about every 25k).

Hope that helps.

 

105k miles isnt that bad on a 2000 model.... i dont believe a cat can be clogged that quick. when is the hesitation? during change of gears? idle or low rpm driving? quick change of throttle pressure?

 

Huh, maybe I should double check the fuel mileage estimates...I thought it was 31 city, 38 hwy or something like that. May have been a bad source.

I forgot to mention it has a new cat conv on it that's just a few hundred miles old.

Hesitation is usually right when I hit the gas from a dead stop...it bogs down for a second or two, then snaps out of it and goes. Sometimes it does it when I'm moving at slow speeds, but that could just be that it's in a higher gear, I didn't push the gas hard enough to make it downshift, and the thing is only 125hp so it's just fuggin slow.

 

Wow, SmikeEvo, thanks for that link too. the 25/34 is also high because mine is the Auto(3), so I should be expecting 24/29. Kinda weak, but good to at least have my expectations more reasonable. Combined is 26mpg, so 27mpg isn't bad.

 

Glad I could help some.

 

Do the wires,02 sensors, fuel filter, pcv valve, caps rotors, air filter. !!

hehehee

 

What about "in order of most likely to be causing the hesitation"?

I don't wanna spend $400 on this car if the most likely of reasons is causing the problem and I can knock it out with one change.

 

thaigleshmk is rt...do whats been outlined....I think at this point if you haven't spent money on continuing maintenance---well its caught up with you...spend the money now and tune it up, change all the filters, check the timing--due the thiming belt if its due, change the o2...they get less responsive and mileage will suffer at 100k... all this will get you everything you can get out of a 100k car...As a side note I drove an SE-R to almost 200k and it still got 30mpg and was the best handling, fastest car I owned with mods...but keep up on the maint.

 

I want to maintain it well, just want to try and attack the problem in order. I just got the car maybe 2 months ago, so far I've had to replace a belt tensioner ($400 at Toyota, my last trip to the dealership), put a new cat on it to fix the CEL, oil, new plugs. I'm slowly but surely getting it all tuned up, just want to do things in order of most likely to cause the performance issues to least likely to cause the performance issues.

No doubt it all needs to be done, just want to prioritize.