Im used to get 18mpg @80mph and nowim getting 15mpg @ 80mph. Ivealso have noticed loss of power climbing a hill i regularly climb i now have to shift out ofoverdrive to maintain 80 up the hill and recently the egr temp valve popped out and they cleaned up the threads and reinstalled it but i still have an engine noise simular to a disieling sound in the rpm range of 2000 to2200 rpm no noise present before or after that range, engine has 226,000 miles and spark plugs have 76,000 on them timing belt has 46,000 miles on it and i have alwaysran regular gas instead of high octane.And it uses about 1.5 qts of oil in 3000 miles

Maybe the engine is just wearing out!

Any ideas what going on here with my power and fuel economy?

 

I would say that it is trying to age a little. lmao

 

Timing belt won't be an issue. Still too young and only affects timing. If it's screwed up, you'll experience worse affects.

I suspect the plugs (& plug wires?) having 76k on them might have something to do with your problem.

Also, I've heard running lower than rated octane my have long term effects on the motor. Perhaps this is one of those.

 

if ur engine is consuming 1.5 every 3000 miles and its been 76,000 miles since ur plugs were replaced then its very likely you have one or more oil fouled spark plugs. i would defineatley start at the spark plugs and wires since its a cheap fix. but if your EGR is damaged or causing a vaccume leak it could cause a change in performance and gas mileage. but also as a mechanic i would have to say as long as your owners mmanual says you can use 87 octane then it shouldn't effect anything but i wouldn't recomend using cheap fuels regularly like arco, suppose this is mostly opinion but using chevorn or shell regularly can go a long way.
although you have probably already done this some other possible causes could be theair filter, fuel filter, ordirty fuel injector(s)

 

What about the ignition coils. I had one go bad on a 96 sr and the miss was at a specific rpm level, can not recall any diesel sound though, but it may be worth
checking out.

 

Is the diesel sound, "pre-detonation" or "pinging" "knocking"? Try a tank of high octane and see if it gets better. You might have carbon built up in your cylinders, which can cause pre-detonation. There are various methods to help remove carbon build up in your cylinders. Look it up on the internet.

I don't think 1 qt per 2000 miles would affect your spark plugs. I would not worry until your consumption gets worse than 1qt per 1k miles.

 

It may be loss due to valve guide seal wear as well.

 

fuel filter

 

Ill try a fuel filter first as far as i know its never been changed