Hello All,

I am the original owner of an ML320 with 73K miles on it. Reciently when the engine reaches 4000 rpm, it stumbles and pulses, like it is fuel starved. CEL codes are P0455, P0460 and P0170. I have an appointment with the dealer for thursday but would like to know as much as possibe about the problem before then. The fuel filter has never been changed, but it has new spark plugs and runs great below 4000rpm. The stumbling problem occurs in all gears and also when revving the engine in neutral. I appreciate any ideas you may have.

Pat O'Rourke

Hi!
On neutral is normal.over run protection.
When you drive ???
Computer dont know you drive is look is on park mode.
Check the connector on transmision.

Thanks,

That makes sense. I already checked under the car for loose connections, but now I will disconnect and reseat the connectors. Oh yes and one more thing, I had the battery disconnected last weekend to install fog lights. During the install I connected and disconnected the battery several times. Could this have upset the computer's memory and caused this problem?

When you take batt,off you need radio codes.
The problem is in no information to computer car is on drive mode.
Try go back - what you done beefore you install your lights.
Disconect your lights.
Look to me is there problem.
When you drive car that problem is appiring?????
On Parking mode is normal.

Hi,

Yes the problem appears while driving in all gear shift selections. I also did not mention that I had my transmission fluid flushed and filled about 3 weeks ago at the dealer. This week is the first chance I have had to drive the car since the fluid change and my wife drives so gently she may have never encountered the problem. I had them recheck the fluid level just before they closed for the New Years holiday and the fluid level is good. There may be a loose connection at the transmission as you suggested before.

Yes,look ther is somthing there,becouse computer dont getting information car is on drive.
You need to go back to dealer.

Probably the mass airflow sensor. Sounds just like it. No, disconnecting the battery didn't cause the problem, but the flywheel sensor adaptation should be relearned and the transmission self-adaptation also.

Gilly

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Thanks for the advise. The MAF is easy to change but is there any way I can test the MAF before buying a new one? Should I try to clean it?

Pat

The best way to diagnose is to have the truck hooked up to a computer scanner which can read the self-adaptation numbers for the fuel mixture. You should also make sure there are no intake air leaks downstream of the MAF sensor. If you know it's bad you can try cleaning it, but I don't think it'll really matter much. BTW if you have a K&N air filter it's probably what ruined the sensor.

Gilly

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a MAF can be ruined by a K&N filter? Is it the oil?? And what happens to the MAF??

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'94 S500 Cpe

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On a hotfilm MAF sensor, the film matrix can get contaminated by the oil if the filter is over-oiled. Hot wire sensors are OK with it. Some say the matrix can be blasted off with carb or brake clean or the like. I say avoid the hassle and stick with a dry filter.
Gilly

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I use a dry filter on the ML and SLK. The Air intake system looks tight and is clean, dry and dust free. I will ask the dealer to check it out. They want $330 for a new MAF which is about the best price I can find anywhere.

Just a thought, could I swap the MAF betwen the ML320 and the SLK320 just to check it out?

Pat

This place has them for $253.50 + shipping

http://www.trademotion.com/partlocator/index.cfm?action=getLocator&siteid=213951&chapter=EPI346&appSectionid=3&groupid=10046&subgroupid=61073&make=67&model=Ml320&year=2000&catalogid=1

I believe those MAF sensors would be identical, you should be able to find the part numbers on both of them.
You wouldn't lose the check engine light right away, but if this is the problem the ML should run correctly with a good sensor.
Gilly

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My car has the 'hot-wire' MAF and I've used K&N filters for 5+ years with no ill effects. Can understand how it could cause a problem with a hot-film type.

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page