P2017-1
MIL ON&Stored&Current
Self-adaptation of mixture formation for right bank of cylinders is at limit value (at idle speed). Enrichment over permissible limit (P0171)
P2086-1
MIL ON&Stored&Current
Self-adaptation of mixture formation for left bank of cylinders is at limit value (at idle speed).: Enrichment over permissible limit (P0174)

Been getting these about every 50 miles, mixture on both banks ramps way up at hot idle indicationg lean mixture on both banks.
Replaced MAF and O2 sensor, no change.

Anyone know what the idle manifold vaccuum should be ? Other suggestions ?

 

What Is The Cause Of P0171?

• Dirty or faulty mass airflow sensor
• Vacuum leaks – PCV hoses, vacuum hoses, intake manifold gasket.
• Weak fuel pump
• Clogged or dirty fuel injectors
• Clogged fuel filter
• Exhaust leak
• Faulty oxygen sensor
• Faulty air-fuel ratio sensor

 

My moneys on a vacuum leak.
I think we will be seeing a lot more of this what with our 15 year old cars now having brittle vacuum hoses.

 

Not mine. Mine is only 12 years old.

And besides, I changed the hoses when I did my valve covers.

 

Thank y'all but my question has not been answered. What is a good idle manifold vaccuum reading for a stock N/A 3.2 engine when fully warmed up ?

 

Found a reference to 9-9.5 psi.

 

Where did you find that ? I searched all through the SM and found nuttin.

 

From a Mercedes site
Torque pro values 154f coolant 800 rpm engine cover removed. Idle is smooth and revs nicely.
Intake in/hg 20.6 - 10 psi
rail fuel pressure 57psi
MAF 3.9 & raises with rpm - is this about right ?
all rubber feels good.
Long term fuel adjustment -9 bank 1 and -12 bank 2
O2 Bank 1-1 and bank 2-1 both transitioning.

Guess I'll try swapping the MAF though readings seem good. Been going on for quite a while just keep resetting then 50-100 miles later comes back.

 

Make sure the seal on your oil fill cap is good, no cracks.

Make sure it is on tight.

If anyone doubts this, pull your oil cap off when the engine is idling, it will run like crap.

Hope this helps.

Jared

 

Why would the ECM be pulling fuel when the code is P0171 ( too lean ) ?

 

What the Autel Benz module is telling me is:
P2017-1
MIL ON&Stored&Current
Self-adaptation of mixture formation for right bank of cylinders is at limit value (at idle speed). Enrichment over permissible limit (P0171)
P2086-1
MIL ON&Stored&Current
Self-adaptation of mixture formation for left bank of cylinders is at limit value (at idle speed).: Enrichment over permissible limit (P0174)

Not sure why the Autel and Torque Pro say different things but both show a vaccuum leak as a possibility.

Think I'll fire it up while reading the manifold vacuum on a big dial and just wiggle things looking fo a difference..

 

Fired up. Manifold pressure sat at 10.1 and dropped to 9.0 in drive or AC on. Stable
Wiggled and jiggled and tickled everything I could think of. Pressure is solid,
New oil fill cap, very tight.

Long term fuel trip sitting on 9 and 12 % Short term cycling from 0 to 3 %) Maf stable, it and vacuum react as expected to throttle.

Driving me batty. About only thing I can do is swap the MAF for another new one (Bosch) I have. Am at the "throwing parts at it" stage.

Problem is that is just occasional and usually at a stop light (hitting brake does nothing). Have exhausted the usual suspects. Any ideas ?

 

Donut gasket on engine cover to MAF not seated properly or torn?
Throttle body gasket leaking air

 

With cover off I tried pulling and pulling and jiggling on MAF and Throttle body. No change in vacuum (had in a big Torque Pro dial.

Did everything I could think of but nothing changed. Replaced engine cover and donut carefully. No change. Tomorrow going to change the oil ant take for a run.

Only outliers are the 9 and 12% long term trim but remember seeing short term go outta sight at stoplight last year. Probably what triggers the light.

Note the fuel trim increase is only at low idle, in crease to 1500 rpm and it drops back to normal.

 

Check EVAP system and gas cap for good seal?
You replaced all four O2 sensors??
maybe the throttle plate isn't closing far enough?

 

Just a thought but occasionally I have a "pending" P0410, secondary air pump but never becomes a fault. Could they be related ?

Gas and oil caps have been replaced and are tight.

Replace primary O2 sensors.

Throttle position looks good and proper change on movement.

 

I was thinking about that secondary air system also as it feeds air into the system. I would certainly check carefully all those associated vacuum hoses and solenoids; the EGR system is attached to the intake manifold as well.
The PCM uses the difference between the front and aft O2 sensors to set fuel trim. Front sensor is primary, aft sensor mostly shows catalytic converter function.
The MAP sensor is also used to set fuel trim in the NA.
Might want to check the contact points on the rely in the RCM for the fuel pump; bad points could be reducing voltage to pump, but I would think that would show at all RPMs.

 

That 10 inch vacuum seems kinda low; I would think some where around 16 at idle.

 

Padgett, I just checked vacuum at idle with a Pensky gauge I bought back about 1965 so it may not be as accurate as yours. I got 17" at the vacuum line at my Needswings oil catch can and 16" at the vacuum line that attaches to the MAP sensor when idling.
You have checked/replaced the "O" ring where the TB attaches to the manifold?

 

A little embarassing but is what happens when you do not have a good baseline. Have to admit the problem has been there since I bought the car about 10k milles ago. Random P017x errors, usually on for each bank.
So I bought a new Bosch MAF and maybe slowed down but did not go away. Perodically I'd check for leaks but never found and and all rubber plastic feels like new (garage kept).

Meanwhile occasionally at a stop after fully warmed up I'd see the fuel trim go bananas. Figured that was causing but why. Yesterday I started tearing into it and took a baseline that looks like this:



Note the high negative long term trims
Year old MAF

New MAF today. Note much lower long term trims. This was about an hour's drive (with stops) speeds ranging from 25 to 45 mph. Both shots taken while parked and idling, AC on.
Trouble is I just checked and there are two P017x errors "pending" though might have been while baselining. I never saw any extreeme excursions though. Guess I'll keep driving a bit and see if returm.
Thanks for all the help.

ps that is an 8" Androd tab, phone could not display enough parameters.