System Too Lean - P0171 (FUEL CONSUMPTION ISSUES)

[Xulfiqar]

its a low cost car for a 3rd world market, They are usually not tuned for stricter emmission standards - hence dumb ecu.

[ahmedstudio]

You mean ECU is not up to the mark?

[Xulfiqar]

no, its been programmed to allow a certain level of slop, e.g. US toyotas will code P0420 at 92% cat efficiency.

yes - you read that correct. even 8% loss of cat efficiency will cause a toyota in USA to throw that code and in a lot of states that means buying a 1000$ cat.

[RehanBhatti]

It is 11 years old. Does it need a new one now?

[Xulfiqar]

Yes, it goes bad at about 60k kms

[RehanBhatti]

Thank you for update. I will replace it soon.

[ahmedstudio]

Wow that's quite an age for an engine part

[RehanBhatti]

Yes it got weak.Thats why engine doesnt go into closed loop at idle.

[Xulfiqar]

1 and 2 wire sensors die early. 4 wire ones work longer

[ahmedstudio]

I had to remove the entire coolant feom radiator (there was a minor leakge in a hose). Anyways, I filled it up with distilled water only and noticed that the engine coolant temperature is behaving correct. i.e between temperatures of 90-96 C whereas it stayed between 76-82 C with coolant+distilled water earlier.

What could be the reason for correct restoration of engine operating temperature now?

[RehanBhatti]

What could be the reason for correct restoration of engine operating temperature now?

Stop the leakage.

[ahmedstudio]

With leakage the temperature should rise high instead of low

[RehanBhatti]

Bhai, your cooling system is not properly pressurized due to leakage.

[ahmedstudio]

So the heat was escaping?

[ahmedstudio]

Yes the pipe attached in to front-right wheel brake is leaking. Is that what you referred to when you said that you saw a leaking brake booster too?

[Xulfiqar]

no, the brake booster is just the big black saucer attached behind the master cylinder, it works off engine vacuum - a bad booster can cause vacuum leaks.

If you have a liquid leak at a wheel - DO NOT DRIVE the car at all. replace/repair the part first.

[ahmedstudio]

What should I check in brake booster for leakage?
Some area of booster itself or it's pipe connecting to engine? From the data you saw in my Techstream videos, is it just an air leak or diaphragm issue in brake booster?
In Techstream what indicates a brake booster leak?

I have been driving car for last 2 months with the liquid leak at wheel? Is it dangerous? And is it only brakes related? It is a very minor leak and I intend to repair it asap.

[Xulfiqar]

brake booster vacuum leak shows up as air leak in the system and you can usually hear it too from the booster.

and for the love of God replace that leaking brake hose. It will suddenly let go and you will lose brake to two wheels on your car.

[ahmedstudio]

Oh ok sir I will get it fixed the first thing tomorrow. Thank you for making me aware, pushing and alerting . By the way, when we loose one brake then do we loose the other opposite brake too with it ? Both in terms of applied force and the physical system? Let's say we had a leaking caliper in front right wheel, so do we have to change the left front wheels caliper too?

Brake booster leak shows up as air leak in system, so there is no dedicated value in Techstream for brake booster? How to hear the leaking air from brake booster?

[Xulfiqar]

The brake circuits in toyotas have been X split since the 70s. Meaning front right and rear left are one circuit, front left and rear right are one.

Its done to prevent total brake failure in case of leak. Also make sure to flush brake fluid out every 1 or 2 years to keep the system working perfectly.

Btw, we use our ears to listen to booster leak