Corolla 99, Long term trim -30

[Neumann]

Hi there all,

Newbie here, So I have this Corolla 99 , which had Misfires codes in all Cylinders and in some specific..

So I was reading to change, sparks , sparks cables, and one ignition coil..

Nothing It didn’t worked, so I read also that could be the injectors, so I went to a mechanic a and changed the Injectors and reseated code, The car stop misfiring and the engine light stopped blinking when going at 50 mph, so that good, we tested for about 30 minutes and no engine light..

So when leaving the shop the light came back, now with code P0172 to rich bank 1..

So now , I am trying to fix it myself I read that cleaning the throttle body would help, bought those Bluetooth readers and bought Torque app for Android..

So I found out that the Long term fuel trim is spiking from -20.3. -38 and is when the code is set and the engine light is turn on, then after cleaning the throttle body the engine light went away and the
LTFTR is stable at -20.3 all the time.. but in the morning when you drive it.. it goes crazy -20.3 -35 -38 and the light comeback and because its rich gasoline is bad..

What could be the problem.. it has a MAP , how do go about to fix this issue?..

Thanks in advance..

Topic

[Neumann]

Anyone ?

[leonard]

Start by having a look at the o2 signal data pid with your scan tool
It should be switching between 0.2V to 0.8V
Is your idle rpm normal?

[Neumann]

[quote=”leonard” post=119374]Start by having a look at the o2 signal data pid with your scan tool
It should be switching between 0.2V to 0.8V
Is your idle rpm normal?[/quote]

goes to 1x at warm up, after its steady at 680..
I have no hesitation, the car drives fine it’s just wasting too much gas..

The O2 sensor was changed a 2 weeks ago..

thanks @leonard

[college man]

check the map voltage and the vacuum line going to it for
cracks or leaks. koeo 3.6 volts engine running with 20″ hg
1.6 volts

[Neumann]

What would be the voltage of the Map..
Hose are all fine, or it would showing symtoms of lean.

[college man]

[quote=”utan” post=119411]What would be the voltage of the Map..
Hose are all fine, or it would showing symtoms of lean.[/quote]

I posted the voltages above.

[Neumann]

@college man,
Misunderstood ur previous post..

[Neumann]

Ok,
Testing Map from battery ground to yellow terminal in map its 3.7 and ground to green 1.5 volts, brown color to battery ground had no voltage at all

[Neumann]

So what i do from there anyone?

[none]

I’m led to believe you’ve got a fuel pressure regulator on the rail. If that regulator is leaking internally, its vacuum source could be sucking up that leaking fuel causing your nasty fuel trims. If the vacuum line isn’t attached to the regulator, that’s going to force full pressure to the injectors too. I wouldn’t know if that full pressure would be enough to cause the fuel trims you’re seeing, but it’s something you can experiment with and find out for yourself while you’re diagnosing the car.

[college man]

[quote=”utan” post=119465]So what i do from there anyone?[/quote]

If you have a vacuum gauge gauge check to see if your exhaust is
restricted or if you don’t have the vac gauge take the front o2
out and see if fuel trims change. Two components that would affect
fuel trim have been checked. something is getting fooled here. :huh:

[Neumann]

This car model has no FPR, Corolla 99..
What i am wondering is if the test I made to the MAP sensor was correct…?

[Neumann]

[quote=”college man” post=119520][quote=”utan” post=119465]So what i do from there anyone?[/quote]

If you have a vacuum gauge gauge check to see if your exhaust is
restricted or if you don’t have the vac gauge take the front o2
out and see if fuel trims change. Two components that would affect
fuel trim have been checked. something is getting fooled here. :huh:[/quote]

Hi, will disconnecting the O2sensor suffice to test?
I didn’t add it in the first post but I changed the O2 sensor 2 weeks ago…
What i am wondering is if the test I made to the MAP sensor was correct…?

thanks again.

[Lorrin Barth]

“I didn’t add it in the first post but I changed the O2 sensor 2 weeks ago…”

You also stated it is providing a steady reading in closed loop which it should never do.

[Neumann]

When I said that I was refering to the Long Term fuel trim, sometimes is steady at -20.3 is when engine light is off, and when in first time in the morning it gets waky , -30 , -38 and the engine light turns on..

Its very strange, O2 sensor changes from 0.1 , 0.8 even 1 volt. but not all the sudden, but o2 sensor bank 1 its waky, from 0.8 to 1 volt but in crazy way..

[Author]

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