Engine Code PO171, PO174.

[prorocke]

I own a '98 with the 4.6L engine. I keep getting a check engine light with engine trouble codes of PO171 and PO174, which I believe are bank #1 and bank #2 running a lean fuel mixture. I also have a shuddering /rattling sound that is alot like spark knock. I only here this knocking whenever the engine is put under a load, such as going up an incline.

Are these problems related?

I have already replaced all four Oxygen Sensors, EGR valve, plugs and plug wires, PCV valve and Fuel filter.

I am suspect of the MAF sensor and/or the coil packs, or maybe even an exhaust leak somewhere.

Any suggestions?

-prorocke

 

[JUST4FUN]

those codes are for unmeterd air. ie. vacuume leak . bad
mass air sensor. look for vacuume leaks first .go to the PCV hose take it off and look for cracks in the hose all the way to the throttle body inspect all vac lines . if you dont find a problem
R&R mass air

 

[prorocke]

I followed your advice and checked for vacum leaks. Everything looked good in that aspect. Next, I followed your advice about the mass air. I found that the wires inside the MAF were extremely dirty. I disassembled the MAF and cleaned those wires with a Q-tip and warm water.
My expy now runs like a champ! It has a significant increase in power with no shuddering or engine trouble codes! -THANKS!

 

[JUST4FUN]

you can also spray it with brake kleen