emissions way up

[bouncer]

Right,
its getting confusing now, just spoke to my friend and he says hes definatly not got a Air mass sensor that he can see, i faxed him a copy of this link

http://www.detali.ru/cat/oem_mb2.as...202F229161&CT=M&cat=19K&SID=07&SGR=040&SGN=01


He says hes got 80 and 17
But not got 5 or 8

We are about 150 miles apart so i cant go and have a look. Does this sound right?

sTeVe

 

[recycled]

could be . he may not have one. my 1996 classic c180 did not have one.
Might need to go the service way, plugs air filter and a good tune up

 

[bouncer]

could be . he may not have one. my 1996 classic c180 did not have one.

Bugger!!! Back to square one.

sTeVe

 

[recycled]

The HC readings should give a fair indication if the cat is shot

p.s please do not shoot your cat. no animals were harmed blah, blah ,blah e.t.c pc madness

 

[Will]

Not all C200s have MAF sensors (MAS).

My 1996/P C200 didn't have one when I had that. I'd imagine there must be a different type of air metering device fitted, maybe either air flow or mass but built into something else (eg, the throttle body)?

Will

 

[Dieselman]

If it doesn't have a MAF or airflow meter then it could be using the MAP sensor to determine manifold vacuum.

This could cause it to overfuel if the vacuum was low.

Get a picture of the engine bay..

there must be a method of adjusting the mixture if the sysem isn't runing closed loop.

 

[recycled]

It will certainly be a closed loop. it just uses the ECU to determine preset values and cannot adjust itself to varying changes in the fuel map system

 

[Dieselman]

Sure, but how does it know how much air is being injested..unless it just uses the throttle body pot...?

 

[recycled]

That is why i want to see the HC reading to see if the cat is shot.
it could use intake manifold pressure. not sure what merc uses but if the HC readings are high as well we can include the cat or the lambda sensor not functioning properly and causing and increase in fuel mixture e.g the engine thinking it is still cold.

my results from start up cold in the winter for 10mins warm up.
fast idle
CO 0.3 max 0.3
HC 37 max 200
Lambda 1.03 max 1.03


on warming up till it got nice and warm

CO 0.08
HC 8
lambda 1.01

 

[Number_Cruncher]

>>How does this engine know how much air is being injecsted?

If there's no MAF, there'll almost certainly be a manifold absolute pressure sensor - from this, the ECU can calculate airflow. If there's a drilling or pipe between the manifold and the MAP sensor, then check this for leaks or blockage.

When warm, the lambda sensor voltage should cycle back and forth, as the mixture is being adjusted, with emissions at the levels stated, I would imagine the lambda sensor output is pegged.

 

[bouncer]

Thanks guys,
i'm trying to get a photo of the engine, and he will find the rest of the emissions results, but it may be tomorrow till i get anything.
I will post again as soon as i have anything usefull.

sTeVe

 

[recycled]

or the cat has been poisoned

 

[Stratman]

I think Number Cruncher is on the right track.

I've just looked up my old Haynes manual for the W202 and for 2 litre engines up to 6/97 (111.941) it says the injection system is Bosch PMS (Pressure engine Management System). The alternative is the Bosch HFM (Hot Film engine Management), which is what we know as the air mass sensor.

It also says that the mixture setting, which controls the CO content, is not manually adjustable. You need to connect a STAR machine or the like to the diagnostic socket. That will read out any faults present in the system.

 

[big x]

Check the flap in the PMS throttle body by removing the large plastic pipe that runs across the engine, these flaps can stick due to gummed up oil deposits.
BTW there is a very good explanation of how this pre-maf system works in the W124 E-class owners bible.

adam

 

[bouncer]

I think Number Cruncher is on the right track.

I've just looked up my old Haynes manual for the W202 and for 2 litre engines up to 6/97 (111.941) it says the injection system is Bosch PMS (Pressure engine Management System). The alternative is the Bosch HFM (Hot Film engine Management), which is what we know as the air mass sensor.

It also says that the mixture setting, which controls the CO content, is not manually adjustable. You need to connect a STAR machine or the like to the diagnostic socket. That will read out any faults present in the system.

Just found this in my old emissions book

c200 (202) ignition system PMS MOT

CO is controlled by ECM and Lambda sensor NO adjustment available
Idle and base idle speed is controlled by the ECM
If idle speed is incorrect check that idle speed control valve is not seized and check for air leaks

Ignition timing is controlled by ECM and no adjustment is available

Cat models are fitted with a conventional heated type lambda sensor
Lambda signal passes to fuel ECM terminal B7 (MP6)
Power supply for heater element originates at fuel ECM terminal B16 (MP6)

Vehicle also has EVAP canister purge system Purge solenoid valve receives permanent power supply from ignition switch (with ignition on)
and is controlled by ECM on terminal B17 (MP6) which switches the earth path for the valve.

Hmmmmmmmmm.