Fault Code 171

[jay926]

hi all

this is kinda a follow on from my previous posts about my engine problems and coolant usage.

well my CEL has come on, fault code PO171 SYSTEM TOO LEAN i believe. well i cleaned my MAF sensor but that hasnt seemed to clear the problem. i have noticed that during the harsh winters and the deep freeze we've had recently, i've noticed that the light went off, but too replace the problem my fuel consumption became considerably worse. the light has since came back on 2 days ago.

does anyone have any advice as to what the problem may be? i thought a bad MAF reading the air flow wrongly hence a higher fuel consumption?

cleaning doesnt help it so would the next step be getting a new one, at £170.......

or is there anything else like maybe the lambda sensor?

any help would be greatly appreciated as im not entirely mechanically minded but i do try.

thanks all and happy xmas.

BTW i have a 2001 celica vvti with 101,000 on the clock.

[215 compressor]

you could check for a split vacuum hose as in an air leak some where as this could give you a weak mixture and cause it to run lean worth a check .

[jay926]

ok cool i'll try that and see if i can find find anything. if not then the mystery continues. thanks for your advice.

today i checked all hoses and nothing appeared loose or disconnected anywhere.so now i'm at a loose end.does anyone have any more advice what i can try? i have noticed when my EML does go off my fuel usage is worse? any ideas why that maybe?

[215 compressor]

ok the code by auto data is .intake exhaust leak,air system.maf/vaf sensor.fuel pressure ,injectors,ho2s sensor .

is there a leak on the exhaust near your oxygen sensor on the exhaust .i take it your engine is 1zze

[cfc1]

Things to check..

O2 Sensor (Bank 1)

Maf Sensor (clean with carb cleaner)

Vacuum hoses an air box connections. (aftermarket filter?.. check connections and that they are routed how the should be... your connections could be sealed, but plumbed up wrong)

Throttle body gasket

Inlet manifold gasket (freezing temperatures can cause problems here)

Purge valve

Personally I would get a smoke test carried out (it's better for this to be done when the engine is cold, when things get to operating temps any leaks could seal with the changes that come with heat), this will indetify the location of any vacuum leaks, then get the voltages checked on the O2 sensor to see if the problem lies with that.

[jay926]

I got this light when i had my engine changed, maybe like you say, the vacuum hoses could be plumbed up wrongly during the engine fit, but how do i know where each hose is meant to be as there isnt a haynes manual or maintenance manual for this vehicle.

so now im thinking that during the engine fit that something has gone wrong, or been put in wrongly. i'll try and get my 02 sensors checked also. would a normal garage be able to check the 02's or would it be a trip to mr T's office? and also with a smoke test?