Click on the link and scroll down a bit. It basically narrows your intake to where it should be and straightens the air so it goes through MAF properly. Some aftermarket intakes throw a cel due to the wrong position or thicker diameter intake.

AIR STRAIGHTENER: 2 Pics (1 as an attachment)

 

imaco: I like an instrument panel without a warning light on as well. Your mechanic has already eliminated a vacuum leak for a potential cause. The opposite of too much air is too little fuel. So checking the fuel pressure and cleaning the fuel injectors, maybe replacing the fuel filter may lead to a fix.
In your case I would try running a tank with Techron Fuel System Cleaner. If you are lucky that will fix it for less than $10.

If that does not fix it then print out this message and take it to your mechanic. Ask him to check things first before throwing parts at it.



Good luck and please let us know how it goes.





A code P0171 may mean that one or more of the following has happened:

• The MAF (Mass Air Flow) Sensor is dirty or faulty
  Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
• There could be a vacuum leak downstream of the MAF sensor
• Possible cracked vacuum or PCV line/connection
• Faulty or stuck open PCV valve
• Failed or faulty oxygen sensor (bank 1, sensor 1)
• Sticking/plugged or failed fuel injector
• Low fuel pressure (possible plugged/dirty fuel filter!)
• Exhaust leak between engine and first oxygen sensor

Possible Solutions

A lot of times, cleaning the MAF sensor and finding/fixing vacuum leaks fix the problem. If you're on a tight budget, start there, but that may not be the fix for certain. So, possible solutions include:

• Clean the MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
• Inspect all vacuum and PCV hoses, replace/repair as required
• Inspect all hoses and connections in the air intake system
• Inspect and/or test the intake manifold gaskets for leakage
• Check for a dirty fuel filter and proper fuel pressure
• Ideally you'll want to monitor short and long term fuel trims using an advanced scan tool
• If you have access, you may want to run a smoke test

 

Hi Tanprotege : I changed the MAF , O2 , Pcv Valve and the mechanic checked everything , no vacum leak , no smoke , no leaking for exhaust , no problem for hoses and I will try for the Techron .. My mechanic did the test with the professional reader( advance scan tool ) for diagnoses and he said that maybe the new MAF sensor has a problem ... not bad if buy another one from dealership but before that I will try Techron , Also my mechanic needs to inspect for fuel pressure and injectors and fuel filter .... also he checked the manifold gasket and no leakage ...

 

If you have a stock maf sensor and air box you will not need an air straightener. If you have an aftermarket maf and tubing not only may you need a straightener but your ecu would need to be programmed for it. When does your engine run poorly? When under light load(closed loop) your using 02 sensor correction. Under medium to high load(open loop) you are using maf sensor for fuel control. If you can pinpoint when your problem happens, you can narrow down the possibilities.

 

Guys ... I went to a mechanic , he checked all hoses and every parts then I changed the O2 sensor and MAF sensor but I still have the problem ... my mechanic said its better to buy a MAF from dealer ... what do you think ? what about ECU program ? I need to program it for adjustment to a new MAF ? what method is the best way to check vacum leak and air intake crack ? when I stopped in intersection in traffic lights the engine rev is low and about 300 400 .... I still have engine light and code P0171 .... :

 

If you not done anything to the air plenum/inlet, the maf for that engine/car is fine. Low rpm at idle tells me low fuel pressure, does this thing have a fuel pressure regulator?

 

Do not waste money on a new MAF sensor. Replace the MAF sensor only if the existing one is malfunctioning. It can be tested!
Here is an example:

I believe you still have a vacuum leak or a low fuel pressure situation. Make your mechanic aware of this or change the mechanic.

 

So the low fuel pressure is for regulator ? injector ? or I need to change the fuel pressure regulator or sensor ? can u send pic of its to me ... I am worry to change it and I will have the problem again ... just I think the engine rev when it is on D and on intersection or stop somewhere the rev is low and its under 600 700 rpm ...

 

CAREFULLY spray starting fluid (ether) around the intake manifold and various vacuum lines as the engine is running, if a leak is found the engine will run MUCH better for a second or two. When spraying its best to use bursts of spray in one area at a time and not holding the button down because IF the worst happens and it ignites you wont have alot of ether there that will burn if you just use bursts.

 

imaco: it is obvious that you are new to automotive repair. I understand that people have to start somewhere. Basically, you are asking for step by step instructions and that would take way to much time and cause a string of Q and A. Please, buy a "Haynes Manual" for your vehicle(s). It will really help you with trouble shooting.
Second: written step by step instructions make things look more complicated than they are. Therefore, I suggest you watch Youtube videos on the procedures involved. It does not matter on what vehicle they show a procedure. Look at several videos on the same procedure.

To your car and the fuel pressure question: I did not say replace the fuel pressure regulator or anything else. I said fuel pressure could be a cause of the problem. That means you want to know if the fuel pressure is sufficient when the idle drops. You need to measure the fuel pressure with a fuel pressure gauge.
So what are you going to do first? Search Youtube for "how to measure the fuel pressure".