Did tune up and lowered my gas mileage... sweet!

[chopsieze]

Well I figured it out... it was an EGR vacuum modulator (there seems to be other names for it too). Cleaned the EGR valve but no difference and after reading more about it found out it was the probable cause. All the auto part stores wanted $150 for it and they'd have to order it. Went to a salvage yard and found dozens of them in from all different year toyotas, lexus, etc. grabbed a couple for $4 and solved my problem.

Ripped mine open to find a 1/4" tear in the rubber diaphram.

Have been getting 30+ mpg for the last few tanks (3-5mpgs better in Jan & Feb 10 degree weather I might add) so I'm pretty happy.

[chopsieze]

I also had a stuck thermostat but the EGR modulator seemed to have the biggest affect.

[akboss]

Originally Posted by chopsieze

Well I figured it out... it was an EGR vacuum modulator (there seems to be other names for it too). Cleaned the EGR valve but no difference and after reading more about it found out it was the probable cause. All the auto part stores wanted $150 for it and they'd have to order it. Went to a salvage yard and found dozens of them in from all different year toyotas, lexus, etc. grabbed a couple for $4 and solved my problem.

Ripped mine open to find a 1/4" tear in the rubber diaphram.

Have been getting 30+ mpg for the last few tanks (3-5mpgs better in Jan & Feb 10 degree weather I might add) so I'm pretty happy.

Nice work! And a cheap fix too, its a gearhead's love story.

[RahX]

The PCV valve, or something related to it, may have been stuck a bit open allowing more air than normal into the engine which COULD HAVE been running it a bit lean. O2 sensors should compensate but nothing is perfect. Just a theory. Try putting your old PCV back in and see . Plugs and wires affect ignition. Fluids affect friction. Air filter affects air and fuel but an old air filter should cause it to run richer. I've never seen one make an engine run lean lol. It takes quite a dirty air filter to affect fuel mileage too. The rating on the sidewall of a tire is the maximum SAFE pressure you can run at maximum load. In a Prism, maximum load would be quite a feat to reach since most tires have a maximum load that is probably near half the weight of the vehicle alone. In a minivan, tires are near max load with just a couple adults in the thing. If you run a tire that is underinflated for the load it is carrying, the tire will get too hot and.. well.. ask Firestone or Ford about that. However, if you run a tire too high at any load, about the same thing happens except it is a lot louder per se. So, in conclusion: if you run a tire too low, it pops, if you run it too high it pops. Run em at 32-35 (unless you are loading the tire or manufacturer spec is higher (they have lots of money if it causes you any grief (I know I know, you can't replace a person))) and don't overthink it. From there, let tire wear be your guide.