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My 06 Corolla has the p0171 engine running too lean code.

Customer Question
I've replaced the MAF, AF...
My 06 Corolla has the p0171 engine running too lean code. I've replaced the MAF, AF ratio sensor, intake manifold and throttle body gasket. Also plugs and air filter. I've smoke tested it and can't find a vacuum leak. Car runs fine just poor mpg
Submitted: 1 year ago.Category: Toyota
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Answered in 1 hour by:
9/18/2016
Toyota Mechanic: Matt, Mechanical Engineer replied 1 year ago
Matt
Matt, Mechanical Engineer
Category: Toyota
Satisfied Customers: 22,444
Experience: BEng, Repaired my own cars and others for 20 years, worked in Formula 1 for 10 years
Verified

Hello

This sounds like a lack of fuel and could be a lack of fuel pressure from the electrical pump at the tank.

1st thing to try is to remove the fuel filler cap and then flick the ignition on whilst listening for the brief ‘buzz’ of the pump

If the connections to the pump are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,

Ideally measure the pressure at the injector rail (should usually be around 3Bar / 45psi +) and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.

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Customer reply replied 1 year ago
How do I check the fuel pressure? There is no schrader valve
Toyota Mechanic: Matt, Mechanical Engineer replied 1 year ago

hello

in that case then you need to plumb the gauge into where the fuel line is fitted onto the end of the injector rail

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Customer reply replied 1 year ago
I'm getting 11.35 v at the pump. I checked the relays and fuses under the hood and I'm getting 12.4v
Toyota Mechanic: Matt, Mechanical Engineer replied 1 year ago

Hello

ok if you have a voltage drop to the pump then its very likely not running as it should

try running a fresh wire directly to the pump from the battery to see if this fixes things

if it does then I'd consider making the new wiring permanent and splice it into the original exit socket on the relay , ensuring that you cut the original wire

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Toyota Mechanic: Matt, Mechanical Engineer replied 1 year ago

Hi

do you still need help?

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Matt, Mechanical Engineer
Category: Toyota
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