Fuel trim lean

spiggotpaddy

I'm getting a p0171 running lean.
Random misfire at idle on all cylinders.
O2 circuit codes was p0138 now p0136.
Apart from a bad idle the car runs fine.
Its a c180 kompresor.m271
Plugs are good, maf clean, throttle body cleaned, can't find any vacuum leaks. New hose under airbox.
New cam sprockets and chain and tensioner.
New cam magnets.






I wonder should I change the post cat o2.
Any thoughts.

PukkaStukka

Post Cat sensor just monitors cat performance and doesn't control fuelling.

What's sensor 1 doing? Is it switching, stuck high or low?

What's the Maf reading at idle?

spiggotpaddy

Maf reading 2.81 g/s

PukkaStukka

spiggotpaddy wrote: »

Maf reading 2.81 g/s

I presumre that's the figure at idle? And it increases when the throttle is applied?

And sensor 1? Can you go a screen grab of the trace??

jetfiremuck

Sounds like vac leak. Spray carb cleaner around the intake area and monitor data stream. Some vac leaks go away once the engine heats up. Ck vac hoses, pvc valve for cracks or leaks.

spiggotpaddy

PukkaStukka wrote: »

I presumre that's the figure at idle? And it increases when the throttle is applied?

And sensor 1? Can you go a screen grab of the trace??

Yes it increases with revs up to about 10 at 3000rpm.
Sensor 1 at idle


Sensor 1 with revs. 2500


I have checked several times for leaks. Even with a stethoscope. Replaced hoses but to no avail.

spiggotpaddy

jetfiremuck wrote: »

Sounds like vac leak. Spray carb cleaner around the intake area and monitor data stream. Some vac leaks go away once the engine heats up. Ck vac hoses, pvc valve for cracks or leaks.

I sprayed carb cleaner all around the intake, couldn't detect any changes.

spiggotpaddy

I tried with a little butane gas cartridge this evening and there's notable change in engine note with this method.
Although the change happens in and around the throttle body, I wonder was it just sucking the gas through the cold air intake.
There is a well-known bad hose under the airbox but I just replaced it last week.
Its all fun with MB . Fix a fault, find a fault. Just as a bonus my front tyre had a sidewall blow out today , that'll wake you up. Was only inspected a couple of weeks ago.

vw4life

There is two lower breather hoses and a check valve under the kompressor that also perish/fail. I always replace them when the upper hose fails

spiggotpaddy

vw4life wrote: »

There is two lower breather hoses and a check valve under the kompressor that also perish/fail. I always replace them when the upper hose fails

Is that a kompressor out job for the lower hoses. The top hose I replaced was like new, although I put on a new one anyway .

vw4life

spiggotpaddy wrote: »

Is that a kompressor out job for the lower hoses. The top hose I replaced was like new, although I put on a new one anyway .

Inlet manifold and kompressor out.
If you look up from under the car and see any traces of oil around the engine mount its probably from the lower breather hoses.
I've replaced loads of them.