Please help with DT P0171- system too lean

[jojomannoh]

Hi

i have been fighting with this error(P0171) for a while now

i have an aveo LT 2006 1.6L

according to the web info.

possible faults are
-vacuum leak
-map sensor
-fuel injection system
-oxygen system

i have replaced the MAP sensor but issue is still there.

i did a carb spraying vacuum leak test but no luck also


i have attached a snapshot of my live data.

the red flags seems to be

1. long term fuel trim of 29.7%----this value is always constant. i know it should be lower but is it supposed to be constant?

2. oxygen sensor 2 is always 0.8---- is this value too high?

3. fuel trim on oxygen sensor 2 is always at 99.2 %. is this right?

4. i want to do a smoke test on the vacuum leak. where is the best place to plug in the smoke tube?
i am thinking at the opening for the MAP sensor, is this right?

[avguy]

Before you go through the work of a smoke test, have you carefully checked the full length of every hose for cracks? Can you post the mileage along with a brief history of prior problems and any work done? And how does the engine sound and feel - any change since the P0171 started happening?

[jojomannoh]

thanks for replying, no cracks in the hoses

my mileage is 140,000.

Car has been rough idling since i bought it a few months ago(it was 135,000 when i got it) and it had a issue with the temperature sensor not reading any value. there was no code at this time.

The code popped up when i got the temperature sensor replaced.

[avguy]

Wow - it was running rough when you bought it? Hope it was priced accordingly! You didn't say anything about the plugs and wires. That's always the place to start with a misfire / poor running. Be aware that oil pooling in the plug wells is is almost automatic as these Aveos get older, and the valve cover gasket normally needs to be replaced in order to stop that leak. However, you can try a quick fix by retorquing the VC bolts to spec in a criss-cross pattern, which sometimes fixes the leak (at least for a while).

[jojomannoh]

ah yes i forgot to add.

the valve cover gasket has been changed, it was leaking but not now.

the plugs and the wires are ok.

[avguy]

So you bought the vehicle running poorly, and new plugs and wires didn't make any difference. Normally I wouldn't put gas quality in the mix because refinery technology and storage has become fairly solid in the US. But I see you're from Ghana, and I have no idea what the standards there are. So perhaps bad gas is possible, clogging the filter or messing up the injectors. Or perhaps the pump is heading south. So given the lean code being set, maybe a good next step would be a fuel pressure test. And if that's ok, then checking the injectors could be the next step.

[jojomannoh]

hmmm ok. i will go for the pressure test.

should i rule out the smoke test for the vacuum leak?
i want to do a smoke test on the vacuum leak. where is the best place to plug in the smoke tube?
i am thinking at the opening for the MAP sensor, is this right?

[jojomannoh]

after 1 year, i finally got this fixed.

no fault seen with the smoke test. The fuel pump suddenly quit on me, after replacing fuel pump no more engine light.

thanks for all your help

PS: i should have done the fuel pressure test as you suggested, but techs were charging too much for the test.

[avguy]

Thanks for posting the outcome and the fix - most never come back and complete what they started. This information will probably help others because these Aveos don't have a big history of fuel pump issues, so it's important to find out that a pump failing may not be quite so unlikely after all.
The pressure test is very fast and easy to do and it's hard to understand why a shop wouldn't want to accept a modest amount for just a few minutes of work.