Got a check engine light with a reduced performance warning. Shut engine off and restarted in hopes of clearing

did not happen

quick scan at local shop said lean fuel. He cleared the CEL and said if it returns would require further diagnosis

Any guesses what this is

 

What was the specific code?

 

strictly a guess : air leak from accordion section of intake tube.

Z

 

PO171

 

Bank 1 combustion too lean

Engine misfire
Air intake leak between MAF Sensor and cylinder head
Fuel filter / system restriction
Fuel injector restriction
IP Sensor fault (low fuel pressure)
Low fuel pump output
HO2 Sensor(s) (1/1, 1/2)
harness wiring condition fault
EFT Sensor fault (low fuel temperature)
MAF Sensor fault (low intake air flow)
Exhaust leak (before catalyst)
ECM receiving incorrect signal from one or
more of the following components:
ECT Sensor, MAF Sensor, IAT Sensor,
IP Sensor, EFT Sensor, TP Sensor

If it appears again with P0174, Bank 2 combustion too lean, then chances are an air leak somewhere from MAF sensor on up to the throttle body and even into intake manifold or a vacuum line, something in common with both banks.

 

When I had that code I cleaned my MAF sensor, intake temp sensor and the throttle intake butterfly valve. When I put it all back I made sure everything was on right and tight. Not had the code since.

 

Shop replaced mass airflow sensor and air intake tube. leaking at accordion section like it was rubbing on hood.
CEL came on again and its back at the shop. Why something common with both banks if lean condition on bank 2. Why not an Oxygen sensor on that side?

Would it be fair to ask the shop for an $$ adjustment since this should have been revealed initially?

 

If I found a leaky intake tube, I wouldn't have changed the MAF sensor, too. Did you get the tube back? It probably didn't rub all the way through or there'd have been both banks lean.

Could possibly be a bad O2 sensor, as you asked. Hook up OBDII sensor and look to see what the fuel trims are, compare bank 1 and 2.

Hard to imagine an air leak at intake manifold on one side, but spraying a little staring fluid along intake & injectors might spike engine speed. Watch OBD2 for jump in rpms or fuel trims. Some engines have a vacuum line on one side of the intake that would create the fault, but I don't recall one on the AJ26 .

Could be a fracture in exhaust before the Cat, so maybe a hose to the ear could discover a hissing or borescope for close inspection. Borescope/endoscope cables are dirt cheap, have excellent resolution and magnification capability.

Use OBD scanner to observe readings from the Engine Coolant Temp, Intake Air Temp, Mass Air Flow, Throttle Position Fuel Pressure and Engine Fuel Temp sensors, (is displayed with your software).

If the ECM is mislead by a deviation between the butterfly position and Throttle Position Sensor reading, throttle body may be admitting more air than the computer thinks it is and conflicts with MAF reading. Too much variation in sensors will cause ECM to back off performance. Maybe O2 sensor on just the one side reads a touch leaner than the other and trips a warning unnecessarily. It won't cost anything to resynchronize the TPS and Pedal Position Sensor. Check out "TPS and PPS adjustment via OBD" in Search.

 

I don’t think the shop was negligent in any way that would merit a discount on future work. Just my opinion of course.

Z

 

I don't think they were negligent I just did not want to pay for diagnostic twice. I did not have to ask they just billed me for new parts and labor

 

So a second visit to the shop revealed leaking intake manifold gasket on one side does not show up until engine is up to temperature. Required a smoke test

So I was charged for intake manifold gaskets , 2, and labor about $700. As it was the same OBD code no charge for diagnostics

 

good news that progress is being made. Hopefully you
can now spend time driving somewhere besides the repair shop.


Z