Puzzling problem!! Weigh in w your knowledge!

C

captaingeoff

Greenie N00B Member
2010 Mazdaspeed3. 88k miles. Getting intermittent P0171 code, lean bank. Have replaced plugs (Ngk perfectly gapped), coil packs, cam and crank posit sensors, MAF sensor, and even the upstream O2/AF mix sensor. Still getting code. Occasionally. Totally random. 10 miles. 30 miles driving. Sometimes a block after I clear it. Car has very minor 'miss' or slight hesitation that most ppl don't even notice, only really good car guys notice when in passenger seat. So frustrated. ECU? Fuel pump? Injectors? Anyone had this problem? Do tell!
Thank you. Cheers, mates. Geoff


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My guess would be and exhaust leak of some sort before the primary O2 sensor.

Modification list?


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Could be the EGR valve being stuck open as well. Have you ever cleaned it? If not, @Raider made a nice write-up on how to clean the valve. Good preventive maintenance.

Best to start with a boost leak test and go from there. That's where I would start.
 
No vacuum leaks. No mods. Newly installed OEM upstream O2/AF sensor was bad, it seems. Got it warrantied by dealer, reinstalled new one, no problems, yet. 300 miles and counting.....


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Littleloogy said:
Could be the EGR valve being stuck open as well. Have you ever cleaned it? If not, @Raider made a nice write-up on how to clean the valve. Good preventive maintenance.

Best to start with a boost leak test and go from there. That's where I would start.
Click to expand...

When I bought the car 6 mos, and 4-5k miles ago, I pulled off intake manifold, EGR valve and hard pipe, walnut shell blasted the intake valves (pain in the ass, but worked great) and the EGR pipe and valve, installed an oil catch can, and put it all back together. No leaks, so don't ask.


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