Emissions. W124 E320 failing NOx - Page 2 - PeachParts Mercedes-Benz Forum

neanderthal · #16 05-04-2010, 03:16 AM

Quote:

Originally Posted by JohnM.

That's true. Continual running of low grade gasoline is not good for the engine. Nowhere in the manual does it say that 87 octane is OK. It's not because Mercedes is trying to stick it to ya, these engines REQUIRE premium gasoline. Conversely, running 91 in your Honda when it only requires 87 is just as retarded.

Even though there is a knock protection system on these cars, there can still be detonation you are NOT hearing, causing engine damage!

If there is a knock, the sensors should pick up on it and pull the timing, That is their function.

macdrone · #17 05-04-2010, 05:56 PM

Only to a certain extent, once you have to much change the adjustment goes no further.

JohnM. · #18 05-04-2010, 06:23 PM

Quote:

Originally Posted by macdrone

Only to a certain extent, once you have to much change the adjustment goes no further.

Yes. The knock protection systems on these cars are designed more for a "bad gas" scenario which is temporary. Not for continual usage of lower octane gasoline. Neanderthal, it's pay a little bit more now, or pay a lot more later (engine failure). Just sayin'!

Also, it is well known, that pre-ignition will cause NOx to skyrocket. This is why you are failing emissions. Pre-ignition (detonation) causes much hotter combustion temperatures, which in turn increases NOx emissions.

neanderthal · #19 05-15-2010, 07:00 PM

Quote:

Originally Posted by neanderthal

Hi all

Question for the collective wisdom out there. My 94 E320 has failed the emissions test in Arizona several times. These are the initial numbers and they have not changed much in any of the subsequent tests

Pollutant Reading Limit Result

Hydrocarbons 0.12 0.80 PASS
Carbon Monoxide 1.13 12.0 PASS
Oxides of Nitrogen 4.74 2.00 FAIL

Latest results. Run with a full tank of premium fuel (I can only find 91 octane,) AND a bottle of 104 octane booster. The previous tank of gas also was premium with a bottle of 104 octane booster. I also ran a bottle of Chevron fuel injector cleaner prior to that and have been running premium the whole of the last few months and driving a lot harder than usual, in case the car "learns" your driving behavior and replicates/ adapts to it as some of the newer ones do.

Pollutant Reading Limit Result

Hydrocarbons 2.19 0.80 FAIL
Carbon Monoxide 3.98 12.0 PASS
Oxides of Nitrogen 4.85 2.00 FAIL

I did reroot the EGR tube from both ends just 4 days ago. I did also spray and remove whatever tar/ carbon build up was partially blocking the intake end of the engine where the EGR tube is attached.

I had tested the EGR valve when I initially did the EGR pipe about 2 months ago. I admit to not testing it while the car was running as prescribed, but when I had tested it, it opened and closed with the application and removal of vacuum.

It would appear that using premium did absolutely nothing to improve the emissions results. And now hydrocarbons are also failing.

Prior to the test the temps were a little high and the overflow hose at the expansion tank is frayed, so it was spewing coolant out of there, and they wouldn't let me test with fluids coming from the car. My fault, I had slightly overfilled the cooling system. I presume that was preventing it from pressurising and ergo making it run hot.

I left, went elsewhere and parked noseup and "burped" the cooling system and returned to the emissions testing station whereupon it failed it's retest with the numbers posted above.

The tech blamed the hot temps (it was running at just about 100C) for the NOx which I thought was bullpoop since that is within the operating parameters for the car. I didn't state that, or inform her that the "high temperatures" stated in their paper work are high combustion temperatures.
The car did sit for about 5- 10 minutes before the test on the rollers, because they had to recalibrate the machine. I assume that is the cause of the HC failure, because the cat had started to cool down. But that is a wild guess at best.

While I love, absolutely love, my W124s, I am getting to the point that their foibles are starting to bother me. And this is just about the straw that is getting on my last nerve.

neanderthal · #20 05-25-2010, 02:47 AM

Just had a thought. What controls the EGR valve? Could that be the fault?