Check Engine light Funny business?

[Designo_E320]

Hi all,
Here is another brain teaser for you guys. Its got me scratching my head.
My CE light came on a few weeks ago and I pulled the codes for MAF. Well I ordered a new MAF but I just wanted to try to clean the old one with the CRC cleaner. I cleaned the hell out of it and guess what? the CE light went off.
Now however, the CE light will come on sometimes and will stay for days until I drive the HELL out of the car basically redlining it a few times on take offs. The next time I start the car afterwards the CE light will be gone for days and then I will take it very easy and then it will go on again until I drive the hell out of it again. When the light is out I can't pull any codes as there are no codes saved. I guess next time I need to have the codes read right when my CE light is on. What would cause this symptom? I will definitely change my MAF but this is weird. My car runs flawlessly. HMMMMMM

[slk230red]

Hey Designo,

Just curious, did you use regular CRC cleaner, or the one specifically for MAF's?

Thanks,

Dave

[Designo_E320]

Originally Posted by slk230red

Hey Designo,

Just curious, did you use regular CRC cleaner, or the one specifically for MAF's?

Thanks,

Dave

The one specifically for the MAFs.

[SunGuy]

Designo,

Did you remove the sensor from the canister/tower and then spray it? Or spray it in place?

Bob

[Designo_E320]

Originally Posted by SunGuy

Designo,

Did you remove the sensor from the canister/tower and then spray it? Or spray it in place?

Bob

Removed it. Does this mean that the sensor is only Half cleaned? I do have a new sensor also but I would like to keep it until this sensor is really shot to hell. My gas mileage is awesome and the car runs flawless. I am however thinking about taking the MAF sensor out again to spray it and also AGITATING it with a VERY soft brush that won't leave a resifue. If I break it then I have a brand new spare one.
What are the reasons for my symptoms?

[lee polowczuk]

people have always told me, just to spray the MAF, never touch it with anything.

also.... when was the last time to o2 sensor was replaced? that could be causing you CEL to come on.

[david s poole]

your maf could be running lean at low rpm's[2500] which might explain the good gas mileage.you will need to scan the live data and see where the adaptions are before going any further.

[blackmercedes]

There is no such thing as a code that specifies the Air Mass Meter is faulty. There is a fuel trim code that will point you in the direction, and then you use the adaptation values to get closer. Also, cleaning an AMM is usually a temporary fix at best, and replacing the component is typically the only way to ensure the fix is done properly.

Pull the codes, read the values and get a proper diagnosis going.

Since you have a known-good AMM, you should read the fuel trim adaptation values with the old AMM in place and then again with the new AMM.

[G-Benz]

Since you went the "clean the MAF" approach, have you gone ahead and changed the air filter as well?

[Designo_E320]

Originally Posted by G-Benz

Since you went the "clean the MAF" approach, have you gone ahead and changed the air filter as well?

yes

[SunGuy]

Originally Posted by Designo_E320

Removed it. Does this mean that the sensor is only Half cleaned? I do have a new sensor also but I would like to keep it until this sensor is really shot to hell. My gas mileage is awesome and the car runs flawless. I am however thinking about taking the MAF sensor out again to spray it and also AGITATING it with a VERY soft brush that won't leave a resifue. If I break it then I have a brand new spare one.
What are the reasons for my symptoms?

Designo,
Removing the sensor, IMO, is correct and corresponds to the directions on the can of MAF cleaner. I agree with the other comment about not touching the filament with anything. There's really no need.

When I did mine a couple thousand miles ago, after the system self adjusted or re-educated itself via the now clean sensor, my engine, like yours, has been running very smooth. If this is 'temporary', then I'll look forward to re-cleaning perhaps a couple times a year given the mileage I drive. To me, as long as the filaments are intact, I'm comfortable extending the life of the sensor thru cleaning.

As to your other symptoms, there are quite a few others in this thread/forum much smarter than me that will have to comment.

Glad this worked out for you.

Bob

Originally Posted by david s poole

your maf could be running lean at low rpm's[2500] which might explain the good gas mileage.you will need to scan the live data and see where the adaptions are before going any further.

I had the same thing happen on my Northstar('97 Eldorado), the lean mixture caused a bad case of pre-ignition. The live data feature is invaluable on scanners, it's paid for itself after two repairs.

A rebuilt MAF from the dealer was $130, throttle response was much better with the new one as well. It took me longer to drive to the dealer and back than it did to do the whole repair, including two test drives.

[david s poole]

your e 320 fuel injection computer has the ability to modify the mixture by 30% in either direction.this is called adaptions by mercedes.your cel is probably coming on because it has adapted to the limit[either rich or lean].until you replace the maf this may be an ongoing experience.