Knock on deceleration

I've noticed that my wife's 95 E320 has just recently developed a very slight rough idle and a knock on deceleration (more noticeable when cold). The car has been fully tuned up (it has 120K+ miles) and my wife swears that
she only puts high-octane fuel in it. I also seem to notice more exhaust smell then usual (but this might just be because I'm paying attention to it). Could this be an indication of a bad air flow sensor? I have no check engine light indication.
Thanks,
Josh
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hmm.. lack of oil going to the engine. Check oilpump. If oilpressure dropping during decel.? Change oil and oilfilter.
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Niels,
The oil level and pressure look good (it does not change with decel and remains at full pressure). Oil and filter were change approx 2,500 miles ago.
Josh

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Maybe try a higher viscosity oil. I have old engine 660.000 kilometers (190 D 2.5 1987). I added chainsaw oil 2 liters and regular 15/40W 5 liters. Making the oil stick better.
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Niels, you should really provide a disclaimer before making such a controversial decision. Richard
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There was a whole thread on chainsaw oil recently, wasn't there.
Votes were 1000:1 against :-)
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I agree on not using chainsaw oil. The car only gets factory spec. oil. Besides, I'm not sure how adding chainsaw oil would make the car runs less rich (I'm pretty sure that is the cause of the knock on decel).
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http://groups.google.com/groups?hl=en&lr=&threadm df225b.0401040906.68555fa0%40posting.google.com&rnum=2&prev=/groups%3Fq%3Dmercedes%2Bengine%2Bknocking%26hl%3Den%26lr%3D%26selm%3D15df225b.0401040906.68555fa0%2540posting.google.com%26rnum%3D2
"my wife swears that she only puts high-octane fuel in it."
Don't even trust this. Now, add some right (high) octane in your tank and also add some fuel additive for the leftovers that MIGHT be low octane.
Now, run the car and make it nice and hot and run at high rpm. for 30 secs.
Tell me what happens - any knocking?
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So far no change with fuel/additive. Will continue to drive it some.
Any idea on how to test if the air mass meter is working correctly (e.g. ohms/voltage)?

http://groups.google.com/groups?hl=en&lr=&threadm df225b.0401040906.68555fa0%40posting.google.com&rnum=2&prev=/groups%3Fq%3Dmercedes%2Bengine%2Bknocking%26hl%3Den%26lr%3D%26selm%3D15df225b.0401040906.68555fa0%2540posting.google.com%26rnum%3D2
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voltmeter
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Any idea on the voltage range for a correctly functioning air mass meter?

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Might be in my Haynes manual - don't think so. Recall reading it is lower than 12v. I don't know. Messure a new cars AMM and that would tell you the volts/ohm.
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Yes. Me :-)
Worked very well and 800 ml. of teflon.
My next oilchange is soon - after aprox 5000 km. and I will put in 1 liter of chainsaw oil and 5.6 liters regular and 400 ml. of teflon.
Engine runs great - less noice at 1600 rpm in 4th gear at aprox. 60km/h. (automatic gear).
I shall listen to the noice when I change the oil.
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On Mon, 22 Nov 2004 16:18:09 +0100, "Niels Ulrik" wrote:

This is the EXACT reason that cars with a FMBSH command a considerably higher price at resale than those that have been personally 'maintained'. Mike
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well, this car was maitainted prior to my ownership at mb autorised. shit job stay did.
since I changed top gasket myself I know I know what I know and it works fine.
give it a go
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On Mon, 22 Nov 2004 19:20:45 +0100, "news.tele2.dk" wrote:

Like I said, this is the *exact* reason that people pay 'overs' for FMBSH. You may be real happy with your car, but who knows what damage you are slowly doing with that, that.... that chainsaw oil stuff? Just because something doesn't explode after five minutes doesn't mean it is a good job, a good idea or good for the car. Why not just put engine oil in your engine, and chainsaw oil in your chainsaw?

You are suggesting that I put chainsaw oil cocktail in my Mercs? I would rather remove my own gall bladder with an oyster spoon :) Mike
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sparkplugs new?
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Yup. Complete 30K service done 5K ago. Oddly enough this just started a couple of weeks ago. I checked the "easy" stuff like the air filter (it is clean).

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how about the catalytic convertor?
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Well, I figured it out. The rough idle was not an air mass problem but rather a busted engine mount. It still has a *very* slight knock at ~1,500RPM when cold, but I'm going to tackle that another day (and no, I'm not considering chain saw oil yet...)
;-)

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