System too lean

[Mikamaro]

Cel P0171 just came up.
I think my hi flow cats might have something to do with it.

Removed the rear 02 reading with my ITSX, doesnt work.
tried adding fuel at WOT by 4%, still popping back.
what else?

[Mikamaro]

Found these to do to most likely solve the issue:

• Clean the MAF sensor. take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
• Inspect all vacuum and PCV hoses
• Inspect all hoses and connections in the air intake system
• Inspect and/or test the intake manifold gaskets for leakage especialy the Driver side.
• Check for a dirty fuel filter and proper fuel pressure
• Ideally you'll want to monitor short and long term fuel trims using an advanced scan tool
• If you have access, you may want to run a smoke test

[Iam Broke]

Popping on decel is the result of the DFCO kicking in, (Decel Fuel Cut Off). IDK if that's what you mean or not. DFCO can be tuned out.

[JANNETTYRACING]

Originally Posted by Mikamaro

Cel P0171 just came up.
I think my hi flow cats might have something to do with it.

Removed the rear 02 reading with my ITSX, doesnt work.
tried adding fuel at WOT by 4%, still popping back.
what else?

An air intake, leak
Vacuum leak
or Exhaust leak are more likely the culprits.

Aftermarket Cold air kits need varying degrees of calibration to keep fuel trims in check.

This code will not set at WOT it sets in closed loop when fuel trims exceed 12%

Ted.

[Mikamaro]

The only thing I can think of that could be the culprit is the fact that last august I've re-oilled my K&N air filter...I might of been too generous. So tomorrow Im getting the MAF sensor clean and will check for any leaks.

[Mikamaro]

Yep! Case resolved. Dirty MAF cause cel P0171 System too lean.
thanks guys.

[Mikamaro]

Well, I might of spoke too soon. I drove 150miles without any CEL since cleaning the MAF & Inspecting all vacuum and PCV hoses last friday.
This morning 2 new CEL showed up with the same as before:

P0133 O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
P0171 System too Lean (Bank 1)
P1134 Oxygen Sensor Circuit - Transition Switch Time Ratio (Bank 1 - Sensor 1)


I'm bummed and running out of explanations...but the funny thing is that the car seems to run better with the code, it seems to pull harder.

[JANNETTYRACING]

Originally Posted by Mikamaro

Well, I might of spoke too soon. I drove 150miles without any CEL since cleaning the MAF & Inspecting all vacuum and PCV hoses last friday.
This morning 2 new CEL showed up with the same as before:

P0133 O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
P0171 System too Lean (Bank 1)
P1134 Oxygen Sensor Circuit - Transition Switch Time Ratio (Bank 1 - Sensor 1)


I'm bummed and running out of explanations...but the funny thing is that the car seems to run better with the code, it seems to pull harder.

Replace bank 1 sensor 1 O2 sensor or switch it to other side and see if it follows or reoccurs.

Ted.

[Mikamaro]

First thing I've done weeks ago when the Cel P0171 came at first, replaced both pre-cat with new O2 sensors.

[Mikamaro]

P0134 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)

I starting to think I might have a wiring problem with the connector to the Bank 1 sensor 1

[Mikamaro]

I left the car to my local shop.
We will see what he ahs to say...

[Mikamaro]

It seems there was a small leak, They tighten the connection from the Hi-Flow cats to the Manifold. Let's see if that is/was the problem...If the Cel comes back, we will change the Gasket next.

[Mikamaro]

The CEL came back, The consensus is that it's because of a bad, weak or flaky MAF sensor. I ordered one. We'll see...

[Mikamaro]

Got the new MAF sensor in last night...after about 20 miles of driving, Lean codes came again..
P0171 System Too Lean (Bank 1)
P0174 System Too Lean (Bank 2)

So perhaps it's time for a tune for my hi flow-cats...