280 SE failed CA smog

[Feather535]

Lucky you - you need the CARB approved one in CA

I hope that's not the only solution -- it's as much as I paid for the whole car!

[john erbe]

How long has your EGR valve been in there?

[john erbe]

How long has your EGR valve been in there?

[Feather535]

How long has your EGR valve been in there?

No idea!  I don't even know where the EGR valve is on this car or what it looks like.

[Alec300SD]

Have you changed the fuel filter yet?

Have you checked the spray pattern of your injectors?
Poor atomization will cause rich running and high CO.
Also if the injector seals have deteriorated, you will have unmetered air.


For a 116024 (280 SE) the injectors are MB Part Number A0000785623.
Injector seals are MB Part Number A0039973048.

[Feather535]

Have you changed the fuel filter yet?
Have you checked the spray pattern of your injectors?

I have replaced or rebuilt everything in the fuel system except the fuel distributor.  Injectors and filter are new.

After all that and adjusting the mixture, I've managed to get CO down to 0.2%, but now HC is too high.  The tech at the test station suspected a missfire and I tend to agree.  I'll go through the procedure of checking every cylinder but suspect I leaned out the mixture too much trying to reduce CO.

[ramiro]

So what did you change to get the CO value below 3%?
What about the ignition system are the wires new , you wrote that one spark plug looked bad so maybe something is wrong there?

[Feather535]

So what did you change to get the CO value below 3%?
What about the ignition system are the wires new , you wrote that one spark plug looked bad so maybe something is wrong there?

On the ignition side, replaced the spark plugs, wires, coil, distributor cap and rotor; in the fuel system, cleaned out the tank, replaced the screen in the tank, the filter, the accumulator and the fuel lines in the rear and installed a rebuilt WUR.  And after all that I set the mixture as lean as I could get it and still maintain idle at 800 RPM.

[ramiro]

Does the idle feel smooth, mormaly a 280se should have no vibrations at idle and if you put your hand at the exhaust there should a continous stream without any irregularities.
Do you have the ability to do a smoke check for vacum leaks, a friends 280 had serveral leaks in the idle air circuit ?

[Feather535]

Latest installment: After the last test, I did the usual checks for misfire, but didn't find a regular miss on any cylinder.  I suspected I had leaned the mixture too much, so I enriched it just enough to even out the idle. 

On retest at idle CO was 0.8% and HC was variable between 160 and 450.  That's a big range, from passing to gross polluter status.  The tech said that kind of variability is unusual and would typically be due to a bad O2 sensor, which of course this car doesn't have. 

Has anyone else encountered this?  I'm wondering the mixture is still too lean so that CIS is periodically proving more fuel, then backing off. 

[Alec300SD]

Binding of the air flow sensor or binding of the butterfly valve on the throttle body can cause a variable idle.
You may want to remove the boot for the throttle body and inspect it for damage and adequate suppleness.
The gaskets under the air flow sensor and the throttle body may need to be replaced.

BTDT on 'The Grasshopper' my prior 1979 245DL wagon.

[Feather535]

Nice Volvo.  I had one of those some years ago and still like them.

The 116 is different, though.  There is no boot on the airflow meter and it doesn't have an O2 sensor like Volvo's "lambda sonde".  The possibility of a biding throttle plate or leaks in the joints between the AFM and the throttle body is worth rechecking, but it's not the idle speed that is surging.  That is steady; it's the HC reading that bounces up and down.

[UTn_boy]

All K-jetronic M-110 engines have a rubber boot between the throttle housing and the air flow plate housing. However, there are two different ones according to the engine number.  Up to engine number 110-985-12-068774 part number 110-141-05-82 is used.  This one is just a just a simple round rubber connector.  As of engine number 110-985-12-068775 part number 110-140-04-18 is used.  This one is the big one that makes up the whole bottom of the air flow plate housing.  Both of these types have to be replaced 40- 50 years later.  Also, I have seen several throttle plate bodies themselves leak where the shaft goes through the throttle plate housing causing erratic idles and erratic CO and/or HC readings. 

[Feather535]

To close the book on this story, the 280 SE passed smog today and is finally registered to drive on the road. 

Turned out the high HC reading was due to excessively lean mixture.  The tech at the test station let me do a little tuning with his machine.  All it took (after everything else I did) was to turn the mixture screw about 1/16 turn toward rich.