The Factory originally said to use premium fuel in the 2.5. They later changed this in a TSB to use regular fuel in the 2.5 where carbon build up was becoming a problem. I have no idea why regular has less carbon build up than premium, I have tried both and can detect no change in power and there is no knocking on either type.

 

Then I suppose I'll stick with the mid-grade just to meet in the middle for a happy compromise... Guess that's a safe bet.

 

I have a98 Mazda Millenia.Does anyone know were the knock sensor is located? I am pretty sure that is the problem area because the engine only seems to knock when I am idling or at a complete stop. Otherwise when I drive the knock is faint if not unnoticable. If anyone has a picture or description of the location I would be greatful.......

 

What size engine do you have, 2.3 or 2.5?

 

Standard 2.5 not the s

 

thanks for the feed back guys!!i got the problem fixed and it has a load of difference! fuel is back and accel is back to. the knock sensor is located right under the intake manifold...right in the middle of the block...i would not try to change it yourself cause i did it and it was a pain in a half cause when you take the intake manifold off you have 2 water bypass vavles that mazda was so nice to put there!!there is a tool that takes it off with out taking the vavles off but i could not get mmy hands on one...have fun if you try..thanks

 

Was anyone able to get info on where to relocate the knock sensor? I have had issue with my 98' milli w/ 165k and need to find afast cheap solution .

 

To be honest with you, i tried most of everything except finding another place to put the dam thing. I eventually just went to the dealer and forked down the money and got it fixed, i did not want to but i just got tired of trying...It drove like a charm but now i have numerous amounts of problems now....good luck man