Mechanics

HOW CAN I KNOW, WHETHER IS BROKEN DOWN THE MAF MASS AIR FLOW SENSOR ?: OR WORKS BADLY ?, I AM DOUBTING THAT IT DOESN’T WORK NORMALLY

2009 Toyota Corolla • 12,500 miles

Dear specialists

During the free working engine the tachometer dart doesn’t keep straight, it vibrates. When I drive and (for example I stop under red light) I keep beak and the tachometer dart always falls down and vibrates, and it seems that soon will close, shut the engine. And one time has been such a kind of thing, during the driving accusingly the engine was shut, and I couldn’t start… after 3 hours I tried and the engine started. The last winter was the problem, in Summer it wasn’t so, in summer was Ok… but now is cold weather and again became so. Maybe that problem is not connected with MAF? Or maybe it’s exactly MAF problem? Toyota Corolla LE 1.8 VVTi 2009

Thank you so much

Avatar
Sargis36
November 9, 2011.



The first and best thing to do is to have the trouble codes pulled. Any Advance or Auto Zone parts sotre will do this for free.
In the mean time check the large vacuum line that runs from the brake booster to the intake for leaks.
Also, performa this quick test to check the brake booster for basic working function; With the car off, pump the brake until the pedal is firm.
Then with your foot on the pedal, start the car. The pedal should drop down slowly with the weight of your foot upon it.
If it does not there is a vacuum leak or a problem with the brake booster.

Do these checks, get the codes pulled and come back to us.

Thank you,

Here we did diagnostic, and it showed the problem code is P0171 …

Then I forget to say ( if is dark ) when I turn on the car lights, the tachometer dart little goes up and keeps so straight, like I would like to be it, and it doesn’t vibrates or falls down, and immediately quite reverse when I turn off the lights

About the vacuum, I will try it, still I didn’t approach the car.

Tiny
Sargis36
Nov 10, 2011.
The trouble code, Po171, translates to, "Sytem Too Lean".
This makes me think there is a vacuum leak.
I would check the brake booster and booster vacuum line as the symptoms you describe indicate a large leak and it seems to be associated with using the brakes.
Let me know how it goes when you get a chance to look at the car and test the booster.
Listen for a sucking or whistling sound underneath the hood when you look for a leak.

I checked the vacuum system, like you explained the way, and it worked exactly finely. By our computer for P0171 codes = is written 1. Lean mix (I think this supposed about fuel) 2. Oxygen regulator 3. Air regulator.

But it's so very strange when I drive the engine force is too much strong, when I push the gaz pedal the car runs swiftly

Tiny
Sargis36
Nov 10, 2011.
But I think if the problem were connected with the vacuum system, in that case the car wouldn’t have so strong force, or wouldn’t work the breaks so normally. Within a day sometimes the problem NEARLY disappear, sometimes appears. I am mostly inclined about some sensor (regulator ) is broken down.

Tiny
Sargis36
Nov 10, 2011.
I think the next step might be to check the fuel pressure with a manual gauge. Most Advance auto and Auto Zone stores laon them out with a deposit. There is a test port on the fuel rail. The specification for fuel pressure is 44-50 PSI at idle. Also look at the vacuum line going to the fuel pressure regulator, this is on the fuel rail at the end between fuel rail and return fuel line with a vacuum hose diaphragm on top, and see if removing the vacuum hose changes the pressure or engine idle.

Thank you very much, I think the cars problem is very probable connected with this last version, you said. In these days I will be engaged in that, and later I will keep informed you.

Tiny
Sargis36
Nov 10, 2011.
Sounds like a plan. I will await the results and we can go from there.

Hi my friend

I didn’t forget you, just all these time I was partly engaged in that problem…. And eventually finally we found the problem.

As a mutter of fact: in front of the engine there is "plastic intake manifold" yes? And a little part of that “plastic intake manifold” was cracked and because of that small crack the engine was working so badly, and tachometer dart was vibrating. We glued it with its same plastic material and now is Ok, no vibrating tachometer, and the Check lamp is off. In any case thank you so much for advising me.

Tiny
Sargis36
Dec 1, 2011.
You are very welcome. That is great news! I am very glad you did not go out and spend any money having it fixed, you did it yourself.
That is great.
Take care and come back to us in the future if you ever need help again.

Dr. C

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