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Discussion Starter #1 (Edited)
Hello again,
So I had multiple fault codes that popped up since a while:

P0171
P0101
P0451
P0446

After changing my air filter, spark plugs, evap sensor, I cleared all of them.

But now, I still have CEL without any fault code. So, I checked my short and long fuel trim + O2 sensor. And something don't work.

At idle speed:
O2 is at 0.9V
Short Fuel Trim is above 5%
Long Fuel Trim is at 20%

At driving speed:
O2 is not oscillating but go to 0.7, 0.8, 0.1, 0.4.
Short Fuel Trim is between -3% and 3%
Long Fuel Trim is between 5% and 10%

Also, I notice a consumption increases. Around 10L/100km instead of 8-9L/100km (winter time).

So I know it may be three things:
  • MAF sensor
  • O2 sensor
  • Vacuum leak
I'm pretty sure it's a vacuum leak and I have a system too lean because of that. But O2 sensor don't work well at driving speed or idle speed. So could you give me your opinion plz?
 

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I'm leaning towards MAF, try this. Unplug the MAF while it's running, you should notice a difference in the way it's running. Then plug the MAF back in. Start it up and drive 50 miles. Any codes that are stored will stay for 50 miles regardless if it the computer is unplugged or not. It has memory to store codes.
 

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Discussion Starter #6
Ok so now the car die at idle speed when I start. I need to push accelerator...

As you say it may be MAF or O2 sensor.

And I didnt get the good sensor. I was monitoring sensor 2 instead of sensor 1. And the sensor 1 is stucked at 1 volt no matter what...

I think it's broken. Do you know how to diagnosis the maf and the o2 sensor in order to be sure ?
 

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P0171 = too lean ~ Fuel pump ... Dirty Fuel Filter.... Dirty Fuel injection...faulty injectors
I would start with the fuel filter ...and do a full fuel system cleaner (Liqui Moly has a great product...ya ya..i love there stuff)
and I Recently I changed the shutter valvel/ vacumm valve solidoid because she was running rough on a cold start...alot smoother now..
 
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