So we started out with oil change and air filter on the 2002 4.6 v8 with 168,000 on it. Progressed on to new gas filter and then went all out and purchased some Mass Air Flow cleaner. All good stuff except the gas milage dropped 5-6 mpgs and a couple of days later began revving up when placed in park. So it was throttle body cleaning time and I just cant beleive how much better the truck runs....very peppy ....but still with the poor gas milage. The local Autozones won't check for codes as there is no check engine light.....but somethings up. What did I do wrong guys?

 

tell autozone to get off there lazy asses and check the codes. the gas mileage dropped after you did the work? maybe some residue was left on the maf? did you plug everything back in? what kind of air filter? possibly oxygen sensors. if they've never been changed then its time for front sensors.

 

lets do some new 02's.... I was just told in my thread that a check engine light doesnt necessairly have to come on to have the 02's reading like crap...

 

Well Mat, the milage did drop after the work and I've cleaned the MAF again with no change. Air filter is a Fram. What specificly are front sensors ?

 

You might have damaged the MAF if all this stated happening right after you cleaned it.

 

the front oxygen sensors are sensors up front on the exhaust pipes. they are the ones that control the a/f ratio. but as 4.6punisher said the maf may have been damaged.

 

Get that fram filter out of there! Bad stuff! Any leaks around that fuel filter? Damage MAF wire? What kind of MPG are you getting? Fuel injector cleaner? Good luck!

 

Is it still over reving in park? Unplug the battery for a minute to reset the PCM and then let it idle in Park for 5 minutes and then with the AC on for 5 minutes. The PCM will relearn the idle and may cure the over rev in Park.

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Toss the Fram filter before you need a motor

Yea , - the 97-03 Fram replacement filters fall apart. The glue that holds the center cone in place doesn't hold after awhile, - it breaks free and the filter gets totally by-passed leaving the engine unprotected.

The worse thing about it is,- you don't know it when it happens.

 

Well I thank you all for the input and we have a happy ending. Went to an Advance Auto parts and told the guy no check engine can you still check codes? Of course he said, and did . Two codes came up, one for the Mass Air Flow sensor and the other for the Air Temp sensor. Well I tossed for the $17.00 air temp sensor, filled the tank and took a hundred mile ride at 65 mph. Topped up the tank again and came up with 23 mpg. Here in the "hills" of Western NC you better beleive I'm a happy boy. Thanks again, hope you all end up with similar stories