'97 E420, 120K miles, repeatedly displays OBDII code P0410 for the last several months. Air pump and clutch are functional but engine fails pump activation test: right cylinder bank mV barely drops below 40 at start of test and then climbs to > 200 by test's end; left cylinder bank initially drops to 100 then rapidly climbs to approx. 700 mV. Oxygen sensors are factory original. Vehicle was exposed to fuel with high sulfur content for approx. 2 weeks in May '04.

Engine performance has been WNL although idle has become rough as of late, despite plug renewal. Are cats partially clogged?

Plugged cats normally cause severe acceleration problems.
I'd be looking elsewhere.
Not familiar with your E 420, sorry.

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2007 C 230 Sport.

I am having exactly the same simptoms like you have described on my s420 1998. On top of that the engine is not very smooth at idle.
Same simptoms with the cilinder bank and my mechanic told me that the left side chain is stretched.
I still have the check engine on.Problem unsolved yet.

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Radu Negru

M119 engines have been known to have problems with plugged air injection passages, just like the EGR tubes get plugged with soot / carbon on M104 engines.


On a cold start, take the rubber hose off of the air pump and feel the amount of air volume coming out of the pump, they usually either work or they don't-not much grey area. If you have air flow from the pump, then the air passages in the cylinder head are most likely plugged. This problem is generally more common on high mileage engines.

In M104 engines, when the "hot inlet pipe to the intake manifold" gets plugged up with carbon, you can either replace the pipe or clean it out.

On M119 engines, when the air injection passages get plugged with soot and gunk, the head needs to be removed and cleaned.

Not a happy diagnosis if that is your problem, but I'm sure you'd rather know before you spend money on a pump and still have the same problem. Good luck.

I also had the following passage copied to my computer:

The system uses the o2 sensor to diagnose the air injection system. After the car has warmed up, it will activate the air pump for approx 60 seconds and watches the o2 sensor voltage-as it blows air into the exhaust system it will drop the o2 sensor voltage-it needs to drop below 40mv within 60 seconds or it will trigger the light. When the air injection system is working correctly it will drop below immediately, if there is a minor restriction it may take a while: 15-30 seconds. The same is true of the o2 sensor is getting lazy, then it may take a while for the voltage to drop, it may not drop at all if the o2 sensor is really bad. Good luck.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

you mean to remove the heah on m119...that implies the head gasket ...chain...tensioners....
What pasages shoud I clean on the head?Sounds like 1500 job if I will do it myself

__________________
New Addition to the family
2013 Passat TDI 5Miles
2004 E500 4MATIC Wagon 95k
1996 E300 Diesel 173k Sold
1993 300E 2.8 230k Sold
1994 E320 White Wagon 373K Sold
Still dreaming about ....500E


Radu Negru

I am not suggesting your problem is due to plugged air injection passages.

I was actually responding to the originator of this thread.

I would be suspicious, though, of the diagnosis that your left side chain is stretched. Either the chain is stretched, or not. There is no difference between the left-side and right-side. It is one chain. Further, M119 engines don't have the same problem with stretched chains like M116 / M117 engines.

If the air injection passages are plugged, then the head must be removed.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

I think suginami hit the nail on the head with the lazy O2 sensor. I've seen this happen MANY times. If you want to do a simple test, try this. Monitor the O2 sensor voltage after the engine is at operating temperature. Hold the RPM at about 2,500 for a few seconds. Then, abrubptly floor the accelerator for a split second. When the throttle springs back to the closed position it will activate the "decel shut-off" feature. The O2 sensor voltage should drop exactly as it would during air injection. If the voltage is close to what it is during air injection the O2 sensor(s) are definitely lazy. Good luck

I agree, for both of the folks here with E420 probs, it sure wouldn't be the worst idea to put some O2 sensors in them.
Gilly

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