Air injection problem. Pro's please help

[DMITRY]

Here we go again. I had this code 11 (Air injection fault) on a diagnostics unit a while ago. Kept taking car to the tech. First he replaced the O2 sensor (and other tune up, I had a post about it). Chk. engine light came on again about a week later. Took it back to the tech, this time he replaced the cooling temperature sensor. Week later the light came on again. MAS sensor was replaced. Now it’s on again ! Same damn code. What could this be? Tech said that he checked vacuum and it was ok (eve though the economy gouge is up a little when car is in gear and stationary) My gas mileage is down to 16-17 mpg and I notice that the power and acceleration is down.



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Dmitry
90' 300CE
17" Lorinsers RS90
Brulen mufler
Clear Blinkers
White gouges(made my own)

[Benzmac]

I don't know what the mas sensor is>

I would think that you have a problem with the air injection not working properly. I would start by checking for a vacuum leak to the solenoid that actuates the valve in the air injection. This is critical for it to work.

Also, there is a test sequence that can be done to verify its operaiton. It is outlined ( the full test) in the 124 CD-1 under the group 14 in the Emmision control catagory.

Good luck We sell the CD's if your tech doesn't have the information needed.

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Benzmac:
Donnie Drummonds
300E
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM
OWNER OF MB AUTOWERKS .COM

[stevebfl]

OK, now I am confused. I let this one go when I first read it, knowing that the only way a 90 300CE could turn a light for Air injection would be if it was a California car.

No having much experience with Ca. emissions I figured I had nothing to add. I read right over the MAS sensor without putting 2+2 together. The Mass Air Flow sensor doesn't start till 1993 on 124 cars. I don't know what they would have replaced on a 90 model unless it was the whole airflow sensor (plate).

Is this a Ca emissions car? If not is it really a 93 or newer as the KE cars shouldn't have a airpump code on federal cars or at least it shouldn't light the light?

Whatever the situation, you might want to get a second perfessional opinion as in my book three strikes and your out! The parts that were replaced (with the possible exception of the O2 sensor) don't seem to be related to your fault code.

[DMITRY]

Yes it is a California car.
What was replaced is something that looked like a big plug in chip (it said MAS on it) which was located behind the cover in the batery compartment. The only other place I can turn now is MB dealership and their screw ups will cost me twice as much.

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Dmitry
90' 300CE
17" Lorinsers RS90
Brulen mufler
Clear Blinkers
White gouges(made my own)

[stevebfl]

Ahhh! The MAS relay. This is a power relay that combines the functions of the fuel pump/kickdown relay with the Klima (compressor control relay). It also adds the load of the air injection clutch coil. Basically it is the current carrier for all the heavy current devices related to engine management.

Its rather hard to evaluate that code as sceondary air injection is only used on cold motors. Whether it is working is evaluated by the ECU using the O2 sensor. Your tech is covering all the bases it seems. He has replaced the sensor used for evaluation, he has replaced the temp sensor I presume because it would be involved with when the system would be activated, and the MAS would be replaced on the concept that the AIR pump clutch wasn't getting electrical activation.

The AIR pump pumps when its clutch is electrically engaged. It blows through a valve that opens under vacuum control. The hoses for air flow and vacuum control must be tight (no leaks). There are two valves between the AIR pump and the exhaust. One acts as a check valve keeping exhaust from going up into the pump and the other checks air from being aspirated into the exhaust after the pump quits. These parts all need to be checked.

Do you live in California? (bg)

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[DMITRY]

Thank you guys, if you don't mind I'll print this out and show this to my tech. I live in NYC but the guy I bought the car from, brought it from CA (used to belong to some basebal player's wife )
Thanks again, hopefuly this time we'll fix it.

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Dmitry
90' 300CE
17" Lorinsers RS90
Brulen mufler
Clear Blinkers
White gouges(made my own)

[mbdoc]

The 1990 California emissions cars use the same system as later LH fuel system cars(for monitoring). The air injection & EGR is monitored thru the O2 sensor & the ignition system(map sensor in EZL). Could be as simple as broken vacuum line from electro-switchover valve to diverter valve. Many Calif cars had a recall on the EGR code 16.

[This message has been edited by M.B.DOC (edited 11-23-2000).]

I had a similar problem with the air injection pump. I think it is the same code as yours but mine is on a 500E. The dealer said that the intakes are carbonized and it costs about $ 3K to fix this. It involves removing the head to get to the problem area. For a second opinion, I went to a trustworthy mechanic, He suggested that since the air injection pump only operates a few moments upon cold start up there is not a big concern and he removed the check engine light... This was obviously not a fix but it got ride of the annoying check engine light.

Please keep me posted with your search for the remedy of the air injection fault problem. I will bring all the replies to this post to my mechanic to get his opinion on them.

Thanks and good luck.

Thanh
500E

[DMITRY]

How did the dealership check this ?
I gave my tech all the replyes as well.
He said that he preaty much did all of it. I am taking the car back to him on tuesday or wednesday for timing chain problem, so it will be back to the "drowing board" with the air injection.
What do you mean by taking the chk. light out?!
He reset it or took out the bulb? My problem is defenately intermitent. It doesn't come during start, ususaly after the car drove for a while. After I reset it (I can easily do it on my car) It stays away for a while, a week or so and pops up again. Usualy if something is broken, you cant reset the light till the problem is fixed.

DMTRY,

Here is what the shop order from a MB dealer for my car when I took it in for the check engine problem:

Follows is the excact write up:
Code 004. Air Injection. Ports for air injection plugged with carbon. checked for codes. code 004. checked to see if air injection valve has vaccum. it does. check activations. The O2 voltage should drop to below 80mV. It does not drop. See recommendations.

Recommendations: Need to R&R both Heads and exhaust Manifolds need to clean air injection port $2600.

Engine harness cracked $800.00.

When I took it to the independent tech he resetted the check engine light after using his diagnostic computer to read a generic diagnostic like "Air Injection pump faulty". I drove the car for about 100 miles and the check engine light came back on. At that time, he removed the speedo cluster and removed the bulb under the check engine square. He also told me that the car will pass smog without any problem since the air injector only works during cold start. BTW, The O2 sensor were replaced by the dealer 10K miles prior this. Apparently, the check engine light has been coming on and off prior to my purchase of the car. The PO has been taking it to the dealer and from the records that i have the dealer did almost everything you have gone through.

Thanh