2002, hard to believe that's an old vehicle now. Rangers (all of them) are extremely underpowered for their size of engine and they all have the same rough idle. I'm not exactly sure what causes it but they come new like that often. That's the Minnesota Ford Motor plant that built most of these (probably unrelated but fun fact.) It could simply be the idle air valve or the sensors werent exactly "matched" to the computer. Higher rpm's seems to satisfy the computer a little bit but they'll always want to bog down. I've tried on many of my Rangers to fix the problem but it must simply be factory tuning and age.

Best answer is Paul H's so I'd go with what he says. Very knowledgeable.

It's a bit of a tricky situation since the two codes may be inter-related...one condition may be causing the other...or vice versa.....or you have two separate issues. Given the age of the vehicle and you don't say miles or any recent tuneups, you may be best to start with a tuneup and clean the TB and MAF...run some Seafoam or Techron...sold at parts stores, etc.. in the fuel tank per label directions to clean injectors and switch to higher grade gas ...89 or 93 octane...for a tank or two...clear codes after the tuneup/cleaning and retest....see if the codes both come back or one does. The low fuel economy, rough engine/poor power and gas smell could all be due to the engine not running at optimum levels due to the code issues.

The P0325 code does possibly indicate a problem with the knock sensor and your truck does have one...located above the oil pan on the drivers side....check for bad wiring, connections or bad sensor...test or replace sensor if needed but the P0325 issue could be caused by the other issues for code P0174...lean condition on bank 2. If the sensor tests OK, move onto checking the other code issues.

Pic of knock sensor location...and info on P0325 code...try another parts store, Ford dealer or online site if the AutoZone guys can't look it up..the pic is from an Autozone website.

http://www.obd-codes.com/p0325

http://www.autozone.com/autozone/repairi...

Ford had a TSB on some issues with knock sensors/pinging problems with low octane fuel ....replace the ignition coil and PCM with upgraded ones if you have excessive pinging or run higher octane fuel.... have the new PCM reflashed at a Ford dealer or shop with proper equipment.

Info on TSB....

http://rockledge.home.comcast.net/~rockl...

http://www.ranger-forums.com/general-tec...

The P0174 code indicates a lean condition in bank 2 of the engine ...passenger side....which could be due to a number of issues like vacuum leaks or bad injector, dirty MAF, etc..or related to misfires from the possible bad knock sensor issue...on the other hand, the knock sensor issue could be caused by the P0174 code issues....lean condition on bank 2. I'd test/repair the knock sensor issue first if there is a problem with the knock sensor or wiring, clear the codes and run some Seafoam or Techron in the fuel tank per label directions to clean the system and injectors. Change plugs and plug wires if they are overdue and change fuel filter/air filter. Check the old plugs when changing to see if any look too blackish....sign of a bad/weak injector.Check for vacuum leaks at vacuum hoses....loose, cracked or broken hoses... check air intake duct for cracks or splits/loose...spray carb cleaner around intake to head areas and TB to intake areas to check for vacuum/air leaks while engine is running at idle...engine speed will change if you spray an area which is leaking. Clean the MAF and Throttle body throttle plate area with spray MAF cleaner ...sold at parts stores....look on Ranger message boards/sites or Youtube on how to clean the MAF and TB. Should be cleaned every few years as part of normal maintenance.

The goal is to get the truck to a proper condition of tuneup and items cleaned which may set some trouble codes if they are a problem and retest to see if those maintenance items took care of the problem or not and go from there.

P0174 info...

http://www.obd-codes.com/p0174

http://www.therangerstation.com/forums/s...

Go to ford, have them connect the ford IDS scan tool up, read the codes, check for ford service bulletins, and diagnose the problem. Don't just slap a MAF on because autozone said that code came up..

Never EVER listen to Autozone employees. They're retail sales people who chose not to flip hamburgers. They're NOT auto technicians nor are they trained to be.

2002 Ford Ranger super Cab XLT 3.0 v6.

P0325 & P0174

So I got the check engine light and I went to get them scanned At auto zone. These 2 codes came up and I was told the knock sensor and Mass airflow sensor were not working. I asked if they had the knock sensor and the computer program they use said this vehicle is not equipped with one. when I asked about P0174, they said to replace the air filter first and see if that works if not, than I should replace the M.A.F sensor or the spark plugs or the spark plug wires. and before this I was told to replace the vapor canister purge valve and the vapor canister purge solenoid. I have low mpg, the truck shakes when Idle & slow acceleration. Fuel is wasted faster if I drive with A/C on. When this problem, started I had a fuel odor anytime the truck was on but not now. Anyone know what is the problem Or any help?