Anybody have any ideas on a 99 SE automatic with codes for Knock Sensor and EGR that are occasionally on but usually off? I am also only getting about 23 mpg but maybe that's acceptable given winter Wisconsin weather.

The CEL lights up, car runs fine, I get the codes, reset the CEL, light out, car runs fine. Month later same thing. Even in good weather I was only getting around 24 mpg...

I have replaced the coils, eliminating the miss under accel, and done all the other recomended maintenance through 60k (car has 62k on it)...

Thanks for your help

 

Clean out your EGR system, remove the plenum for a full job; or just clean the EGR tube in the back- it's kind of tight back there...to get by and eliminate the flow code. (the KS code may go away too) Mine did.

 

Bad knock sensor on my car was giving me bad mileage and surging acceleration.

 

Does a bad KS trigger a CEL. I have about the same problem but my CEL is not lit. Sometime late last year early this year, I did get the CEL. The car ran fine no bad mileage etc. since I had the extended warranty, I took it in and the stealer replaced the O2 sensor claiming that's what the code was for. Since I pulled out of there, the car had not felt the same. It has lost all its peppiness. I did take it back in. But they said replacing the O2 sensor should not have caused a power loss and would need more diagnostic money. My gas mileage went down since then. In all city driving, I used to get about 325 to the tank when the low gas light came on. Now, I only get somewhere between 275 and 300 miles.

 

A bad KS does not trigger a CEL, but if you check for codes it will show up as 0304.

 

24 mpg isnt bad. 23 isnt either. When I get over 20, I jump for joy.

Fill your tank. Drive on the highway at 55mph for 45 mins. Then fill up again and see how much your car needs. The EPA does testing on a weighted dyno at 55mph.

If you do 90 all the time you wont get good mileage. I'm sure someone else will post how stupid I am and they do 90 all the time and get 30 miles per gallon.

I can only tell you information based on stuff I know.