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]

I did that, Ran the car for 40 miles and the LTFT didn’t change from -20.3..
Very strange but then it throw a code about O2 upstream sensor header failure…

So no it didn’t move LTFT , I am lost..

Something I tried was taking out the hose that has the MAP sensor and discovered the throttle body , with ignition key all the way but car off I moved manually the gas accelerator and the LTFT changed to -5.5 , if I let go the LTFT went back -20.3 , the car wasn’t on but that was something that caught my eye.

any comment @college man?

[college man]

Try unplugging the map connector to see if fuel trim comes positive.
Put the o2 back in.

[Neumann]

Did it, disconnected the car wont start, if just turn the ignition key the LTFT wont change regardless..

Only changes to -5 when i open the throttle and accelarate manually.

[Neumann]

I was messuring voltage of the upstrame 02 sensor socket , with car running when testing some of pins I saw the LTFT when to +2 , could it be a bad 02 sensor that is doing all this mess?

[Lorrin Barth]

To test an O2 sensor at its plug you have to be careful. Two of the pins have battery and ground for the heater. Get across those and end up with a black face. With all due care and ingenuity to protect against shorts, put your VOM across the other two pins set to volts and run the engine.

That or pierce the wires at a convenient location. Hopefully there is a plug without battery voltage on it you can get into.

It either works or you need another.

[Neumann]

Thanks,

I didn’t test the O2 but just the socket.. But today my car came with insufficient cooling temp to closed loop gas..

And my O2 sensor doesn’t got over 0.2 volts meaning is death…

So I know is not the computer because I tested the socket again there is voltage and also responses when tested..

[Neumann]

Does Oreilly exchange O2 or I am just done with this one that died?

I know is death, i tested just the socket and saw fuel trim go rich or lean with input from tester voltage..

[Neumann]

Something is really wrong, The O2 wasn’t responding and later at night it started working and coming back home stopped working..

This is annoying and got my head smashing the wall..

[Lorrin Barth]

Look on the bright side – you are getting an education without having to take out a student loan.

[Neumann]

[quote=”barneyb” post=119947]Look on the bright side – you are getting an education without having to take out a student loan.[/quote]

Sure is, I do a little programming which isn’t any related to this but it really fascinate me..

Question if you can answer it.. I read somewhere that you need to 18 or 17 inches of vacuum for an engine to work fine.. does that number is when engine is running idle or it must be maintained at all time even running at 55 mph ?

Ask that because when idling i see good numbers but when pushing in freeway goes down to even 5 inches..

I have changed the O2 again, and now is switching again just fine.. but still rich..

Also I couldn’t get a pic showing how low the vacuum went when running..

Attachments:

• vacuum.jpg

[Lorrin Barth]

You will only see high manifold vacuum at idle. The engine is trying to pull air out of the manifold but the throttle plate is closed. Going down the highway the throttle plate is open.

Occasionally you see cars with economy gauges. All this is is a vacuum gauge built into the dash. If you keep the pointer in the economy range vacuum is high. Also, the throttle is mostly closed and you aren’t going very fast so it isn’t hard to figure out why this is economical on gas.

[Neumann]

ok, I know is been long time…

I’ve tested the MAP sensor… and instead of decrease the volts increase it… from 3.5 and so forth..

Has anyone seen this before I think the sensor is bad.. what do you guys think?

[Neumann]

bumping thread..

[Neumann]

So after all I did to the car where I couldn’t find why the car was so Rich, end up being the Injectors the Mechanic installed Denso Brand for Highlander 2001 to 2004 , Once I bought the correct one and installed them the LTFT came to normal specs…

All this confusion because a stupid mechanic to get the money used the wrong injectors, I am Computer Tech and if your you do know you can’t install an AMD socket A CPU in a InteL 775 socket because is not compatible…

Maybe isn’t the same in engines because they the same size and all but common just make me angry..

So At the end , don’t use Highlander Injectors in a 99 corolla for god sake the increase in fuel will Rich up the gas mixture and will give you a P0172 code.. running to rich in bank 1..

I should sue this idiot since now I don’t know if the catalytic is trashed.. thanks posted so google indexes this post and some other poor soul might get a clue of what happening and fix his issue…

[college man]

Thanks for the update and the fix. 🙂

[Author]

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