Help dont want to use mechanic

[Yisroel K]

Hello, I bought a 1999 4runner about 2 years ago. The truck ran great until about 6 months ago I went to mechanic to fix breaks and rotors. The mechanic ended up switching out both axles, 4 breaks and rotors, and he told me he welded up my muffler. about 4 months ago the muffler sounded really bad but the truck was running fine so I left it. a month ago my check engine light came on with p0170. I went under the car to see it any hole on muffler (i though maybe check engine light from muffler) I saw the rear o2 sensor unplugged and hanging. I went to the store-bought a new gasket and put it back. the truck sounds great but engine light is still on. the truck is running really rich (100 miles per tank) I checked for vacuum leaks and cleaned the MAF but doesn't seem to help.

Please help.

 

[sleepydad]

Hello, I bought a 1999 4runner about 2 years ago. The truck ran great until about 6 months ago I went to mechanic to fix breaks and rotors. The mechanic ended up switching out both axles, 4 breaks and rotors, and he told me he welded up my muffler. about 4 months ago the muffler sounded really bad but the truck was running fine so I left it. a month ago my check engine light came on with p0170. I went under the car to see it any hole on muffler (i though maybe check engine light from muffler) I saw the rear o2 sensor unplugged and hanging. I went to the store-bought a new gasket and put it back. the truck sounds great but engine light is still on. the truck is running really rich (100 miles per tank) I checked for vacuum leaks and cleaned the MAF but doesn't seem to help.

Please help.

you need to clear the code. once the code is stored the check engine light will stay on. you can clear the code with one of these readers. hopefully there will be no new codes?

I have a cheap code reader and torque pro(app) on a cheap android tablet.

I think it was this one... then you need scanner software usually on your phone or tablet.

Amazon.com: Bafx Products - Wireless Bluetooth OBD2 / OBDII Diagnostic Car Scanner & Reader Tool for Android Devices - Read/Clear Your Check Engine Light & Much More: Automotive

 

[Yisroel K]

Codes

Sorry I forgot to mention I did clear the code and it came back on.

 

[Doc2012]

once the code is stored the check engine light will stay on.

This is not true.

The code will stay as long as the condition that caused the code to be present in the first place still continues.

Plenty of times, in my 4Runner and my VW, I had codes, replaced the necessary part, and the code was gone.


OP, it’s very possible that there is another condition to cause the code to be present.

Have you tried anything else? Looked for leaks, done any other kind of investigating?


Sent from my iPhone using Tapatalk

 

[Dieselchessy]

So if the mechanic had to weld your muffler, and then the rear O2 sensor nuts backed off (?), then what does the front O2 sensor look like?

I’m assuming your loud exhaust was due to the O2 sensor falling off?

Having trouble understanding this as generally exhaust bolts are rusted and hard to remove.

The front O2 sensor is the one most responsible for fuel mixture, not the rear one.

 

[Yisroel K]

So if the mechanic had to weld your muffler, and then the rear O2 sensor nuts backed off (?), then what does the front O2 sensor look like?

I’m assuming your loud exhaust was due to the O2 sensor falling off?

Having trouble understanding this as generally exhaust bolts are rusted and hard to remove.

The front O2 sensor is the one most responsible for fuel mixture, not the rear one.

When I put the rear o2 sensor back on I had to use a whole bunch of washers because the bolts where somewhat striped.

Loud exhaust went away when I put o2 sensor back in its place, so I guess so.

The front o2 sensor is otherwise known as af sensor?
It was in its place should I take it out and clean it somehow?

 

[Thebeastlives]

If your sensor was just hanging it might be damaged. Try replacing it and then clear the code and see what happens. Mechanics are people too and they make all type of errors. If you really know your truck is running rich then chances are it is 1 of your 2 sensors.

 

[Yisroel K]

If your sensor was just hanging it might be damaged. Try replacing it and then clear the code and see what happens. Mechanics are people too and they make all type of errors. If you really know your truck is running rich then chances are it is 1 of your 2 sensors.

Is there a way to clean the sensors?
Is there any tests to be done before just replacing the sensor and not know what it is?

 

[Thebeastlives]

You can use contact cleaning to clean them but if it was bouncing around underneath your truck it could be just damaged. I'm not sure you can test whether it is working or not.

 

[Yisroel K]

You can use contact cleaning to clean them but if it was bouncing around underneath your truck it could be just damaged. I'm not sure you can test whether it is working or not.

Does the truck fall into a default mode if I unplug one of the sensors?
If so I can eliminate which sensor is the bad one.

 

[Bad Luck]

Hello, I bought a 1999 4runner about 2 years ago. The truck ran great until about 6 months ago I went to mechanic to fix breaks and rotors. The mechanic ended up switching out both axles, 4 breaks and rotors, and he told me he welded up my muffler. about 4 months ago the muffler sounded really bad but the truck was running fine so I left it. a month ago my check engine light came on with p0170. I went under the car to see it any hole on muffler (i though maybe check engine light from muffler) I saw the rear o2 sensor unplugged and hanging. I went to the store-bought a new gasket and put it back. the truck sounds great but engine light is still on. the truck is running really rich (100 miles per tank) I checked for vacuum leaks and cleaned the MAF but doesn't seem to help.

Please help.

Your problem is likely the front oxygen sensor. The front oxygen sensor monitors fuel trim and the rear oxygen sensor monitors catalytic converter function.

 

[Yisroel K]

Your problem is likely the front oxygen sensor. The front oxygen sensor monitors fuel trim and the rear oxygen sensor monitors catalytic converter function.

Is there a way to tell without replacing it?
Don't want to spend money and not be the issue.

 

[Yisroel K]

Your problem is likely the front oxygen sensor. The front oxygen sensor monitors fuel trim and the rear oxygen sensor monitors catalytic converter function.

Hello, I bought a 1999 4runner about 2 years ago. The truck ran great until about 6 months ago I went to mechanic to fix breaks and rotors. The mechanic ended up switching out both axles, 4 breaks and rotors, and he told me he welded up my muffler. about 4 months ago the muffler sounded really bad but the truck was running fine so I left it. a month ago my check engine light came on with p0170. I went under the car to see it any hole on muffler (i though maybe check engine light from muffler) I saw the rear o2 sensor unplugged and hanging. I went to the store-bought a new gasket and put it back. the truck sounds great but engine light is still on. the truck is running really rich (100 miles per tank) I checked for vacuum leaks and cleaned the MAF but doesn't seem to help.

Please help.

The code is p0171 system too lean bank 1.
Freeze frame
Fuel system 1 status: cl
Calculated load value: 20.4%
Ect: 84c
Short term fuel trim bank 1: 19.5%
Long term fuel trim bank 1: 39.8%
Rpm: 695/min
Vehicle speed: 0mph



Should I do a vacuum exhaust test?

 

[Bad Luck]

Is there a way to tell without replacing it?
Don't want to spend money and not be the issue.

Besides checking every other thing that cause cause a fuel trim issue, not really.

 

[Yisroel K]

Besides checking every other thing that cause cause a fuel trim issue, not really.

I guess I'll have to switch it out.
My o2s11 is reading. 640 volts
My o2s12 is reading 0.000 volts and get it to 0.010-0.020volts on a 2500 rpm Rev.
Is that normal?

 

[Yisroel K]

1999 4runner

What should my a/f sensor ohm reading be?
Mine is at 15
I have error code p0171, System lean
The truck is running very rich.

 

[gamefreakgc]

Is there a way to clean the sensors?
Is there any tests to be done before just replacing the sensor and not know what it is?

You can try soaking the sensor in Acetone overnight (nail polish remover if your girl like to paint her nails) and that can help. Worth a shot if you're tight on funds.

 

[Yisroel K]

You can try soaking the sensor in Acetone overnight (nail polish remover if your girl like to paint her nails) and that can help. Worth a shot if you're tight on funds.

That seems like a cheaper way. Ithink I'm going to try that First , will let you know what happens.
Ever had check engine light with p0171?

 

[gamefreakgc]

That seems like a cheaper way. Ithink I'm going to try that First , will let you know what happens.
Ever had check engine light with p0171?

Yes several times. It normally means you have a vacuum leak but with an O2 sensor hanging out in the free air I'm guessing that's the problem. If not, check out Eric the Car Guy's vacuum leak check video on Youtube, only costs a $3 can of carb cleaner to check.