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]

Here is a pick when the engine light is off…

and the O2 bank 1 sensor , is it the upstream? I remember it was the one in the back of the engine….

Attachments:

• Corolla99.jpg
• corolla99_o2.jpg

[Neumann]

so it doesn’t ring the bell those pics?.

[Neumann]

@college man,

Where is the front O2 located , is it the close to the radiator, I am a bit confused when it comes to sensor position, it seems to have lots of them..

Also can u check the pics i posted.. do u see anything ?

[college man]

[quote=”utan” post=119625]@college man,

Where is the front O2 located , is it the close to the radiator, I am a bit confused when it comes to sensor position, it seems to have lots of them..

Also can u check the pics i posted.. do u see anything ?[/quote]

The front or upstream o2 is located in back of the radiator in
the exhaust manifold. The wave on the top graph does not look
smooth. With removing the upstream o2 and running the car I wanted
to see if the fuel trims started to go positive instead of negative.

[Neumann]

I wasn’t able to find it, or I unsure is the correct one…

I disconnected the O2 that was replaced and I thought the bank 1 x2 but actually is the bank 1 x1
which i am totally confused, the one u are indicating me to disconnect hasn’t been changed since bought car…
What is it suppose to do the O2 u are referring the upstream front O2..?

i am confused…

Disconnecting the downstream the car never got to closed loop.

Attachments:

• LTFT.jpg
• closedloop.jpg

[college man]

[quote=”utan” post=119639]I wasn’t able to find it, or I unsure is the correct one…

I disconnected the O2 that was replaced and I thought the bank 1 x2 but actually is the bank 1 x1
which i am totally confused, the one u are indicating me to disconnect hasn’t been changed since bought car…
What is it suppose to do the O2 u are referring the upstream front O2..?

i am confused…

Disconnecting the downstream the car never got to closed loop.[/quote]

The down stream o2 does not input on fuel/air mixture.
The upstream one closest to the engine will have input
to the ecu to make fuel mixture adjustments. I think your
on the wrong o2.

[Neumann]

Ok,

I find out that the one changed is the one back in the engine aka downstream o2 sensor right..

Now the one u are telling me to disconnect if in front of the engine close the radiator aka 02 upstream right?

so is the 02 upstream the one never changed, do you think is the one faulty?

[college man]

see if this helps. It might be in the back.

[Neumann]

yep, the first video is the one I am taking about it was changed and just disconnected…

So that’s the upstream ?

No what , I disconnected that one and it didn’t change nothing in the LTFT numbers..

[Neumann]

[quote=”college man” post=119643]see if this helps. It might be in the back.

http://www.youtube.com/watch?v=dg_S8fbtU00%5B/quote%5D

So now what? if the LTFT didn’t change does sound fishy to me.. I can see is working because when disconnected that sensor shown 0v , but the LTFT was still stuck at -20.3 can u tell me what to do?

[Lorrin Barth]

Once in closed loop the upstream O2 sensor, the one closest to the engine, monitors the amount of oxygen in the exhaust. When the mixture entering the engine is rich the O2 sensor voltage increases. The engine’s computer then commands the fuel injectors open a shorter period of time. As the fuel mixture goes lean the O2 sensor voltage drops and the engine computer commands the fuel injectors open a longer period of time. In this way the fuel mixture is held close to the optimum.

The downstream O2 sensor (behind the convertor) is monitoring the catalytic convertor operation and its only purpose is to notify the owner that the catalytic convertor is failing but the computer may set a code from this if the engine’s fuel mixture is way out of whack. One of the catalytic convertor’s jobs is to consume any unburnt fuel and if the engine is very rich the catalytic convertor may not be able to burn all the fuel sent its way.

The LTFT is an adjustment the computer makes to try to get the fuel mixture back to where it should be. It could be the O2 sensor is not working but the computer thinks it is or maybe you have a leaking or stuck open fuel injector.

BTW, the LTFT is not going to change immediately once the engine is repaired. Long term means exactly that and the correctly running engine may have to operate a few minutes before any change is seen in this number.

[Neumann]

Ok,

But the upstream sensor is new, so it can’t be the faulty one..
When you said LTFT should start changing after a few minutes of use, do you mean that it could stay stuck a full 20 miles drive at -20.3 and when only change when you going uphill -5 LTFT ?

Because sincerely that number and pics that i shown is like LTFT is stuck..

I am not getting any other code but p0172 , should i be getting a code if the Catalytic weren’t working on specs?

[college man]

[quote=”utan” post=119644]yep, the first video is the one I am taking about it was changed and just disconnected…

So that’s the upstream ?

No what , I disconnected that one and it didn’t change nothing in the LTFT numbers..[/quote]

Did you unplug it or remove it? If you could remove it and see what happens.
you will also need to reset the code. Did you ever check manifold vacuum with
a gauge?

[Neumann]

No i disconnected connectors…

No I don’t have that kind of tool to test Manifold Vacuum..

So u want me to remove the upstream O2 sensor and running as it with code reseated?

[college man]

[quote=”utan” post=119715]No i disconnected connectors…

No I don’t have that kind of tool to test Manifold Vacuum..

So u want me to remove the upstream O2 sensor and running as it with code reseated?[/quote]

Remove the sensor and run the car. If you can plug it back in.
see if fuel trims come positive. reset any codes before the test.

[Author]

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