'93 320CE stumbles on acceleration

Hi! I own a '93 320CE and was very satysfied so far. It is equipped with 4-speed automatic gearbox. Few months ago I noticed that sometimes, when I want to
accelerate hard from low revs, car has something like a small missfire and when it picks up revs (from 2000rpm) pulls hard to the red line. I thought it must be something with plugs or so and didn't take it seriously. After I replaced the plugs and checked coils and wires I was fine for a few days. At least I thought so. Then it happened again, and gradually became much worse over the time. I was at different mechanic shops since then but none of them could find what was actually wrong. As previously mentioned, the car gradually began to missfire more and more and now I'm driving it very slowly with very gentle acceleration. This way I don't have missfires but I'm taking about 25-30 sec from stand still to 60mph! Now, I would like to point out that some shops say that the problem is strictly electrical (ignition problem) and others say it is not neccessarily so. They say it has something to do with a fly-by-wire throttle and a fuel supply and not the ignition. My throttle is partly mechanically operated (can be opened 20% mechanically) and partly fly-by-wire(from that 20% till WOT is managed by fly-by-wire). So I don't really know am I experiencing really a missfire (ignition) or it stumbles on acceleration because of lack of fuel? The only known way left to me to solve this problem is to take the car to a Mercedes dealer. I know they will repaire it for sure but I don't know weather the cost of such repair would be greater than a value of a '93 car! If someone experienced similar problem help would be greatly appreciated! Thanks Mario
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I believe your car is one that can have degraded wire insulation. This could be your problem. Carefully inspect some wires that are visable out of the covering. The water outlet at the front odf the engine has a few sensors and is a good place to check. Replacement wire harnesses are available aftermarket or from the dealer.
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When you mention checking, did you mean also to check sensors? If so, where can I find values for the valid sensors so I can compare them with readings from my sensors? Is there some site on the internet wich contains a database of such things?
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No need to check the sensors, just the wires connected to them. The wires themselves will not look "worn out"- the insulation will be be cracked and flaking away.
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Ok, maybe I used the wrong expression but I meant that insulation is cracked. As a matter of fact the insulation of all wires is in rather poor condition. Maybe it would be best if I used an aftermarket wire harness. Where can I get one in US (since I'm not from US) and what is the difference between aftermarket price and the dealer price? Wich one would you pick?
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You need to make sure the wiring harness from US cars is the same as your car... otherwise, the wiring harness is useless.
Some folks who are handy, simply change one wire at a time and solder them into originall harness. Would be cheaper but time consuming.
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I believe the wiring harness sold by the dealer or aftermarket is the same. As Tiger mentioned the US harness may not be suitable for your car. The price difference is around $100. But I would buy from a dealer in your case to be sure of getting the correct harness.
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Just to be sure we talk about same prices; I visited a dealer and he quoted me some 1500 USD for the harness. Is the price similar in US also? Nevertheless, I'll check about differences between US and EU models. If I find them to be identical and cheaper in US then I would like you to tell me where can I get it in US (aftermarket). Thanks for helping me with this issue!

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http://www.buymbparts.com
I do buy parts from this guy... There is two different model harness depending on your VIN number. If you can get the part number of your harness, then we can match it up. His price is $922.
Another place... http://www.bmaparts.com has it for $844 and $902. This place I know does ship oversea.
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Regards!
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Get part number from your local MB dealer for your engine wiring harness and then have Rusty figure it out at buymbparts.com.
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If your engine is still the original 104992 12 022297, the correct part number is 124 440 5232 (up to engine serial number 072236).
Still, be suspicious of the MAF.
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I'll check that. Thanks!
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Your engine ID should then be 104992 12 022297 and matching wiring should be 124 440 5232 (up to s/n 072236).
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Your engine ID should then be 104992 12 022297 and matching wiring should be 124 440 5232 (up to s/n 072236).

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For sure the harness should be replaced or repaired (I repaired mine, but only as a temporary solution..... now it has been there 2 years).
And for sure, the problem could be the MAS causing too lean mixture. Be careful to continue driving if this is the case. The catalytic convertes may overheat then and blow their ceramic material into the muffler system. Such repair will be very expensive (happened to me... some 5.000$).
One more thing it could be is the camshaft advance, which shall retard below 2.000 rpm. If not, the engine runs erratic at low revs. Camshaft advance electro magnet is at the front of the cylinder head (under the plastic cover at the front of the engine). It is energized through your bad wiring harness, and the wires may be short circuited.
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wrote:

For sure the harness should be replaced or repaired (I repaired mine, but only as a temporary solution..... now it has been there 2 years).
And for sure, the problem could be the MAS causing too lean mixture. Be careful to continue driving if this is the case. The catalytic convertes may overheat then and blow their ceramic material into the muffler system. Such repair will be very expensive (happened to me... some 5.000$).
One more thing it could be is the camshaft advance, which shall retard below 2.000 rpm. If not, the engine runs erratic at low revs. Camshaft advance electro magnet is at the front of the cylinder head (under the plastic cover at the front of the engine). It is energized through your bad wiring harness, and the wires may be short circuited.
This is something I hear for the first time but really makes sense to me. Thanks for the advice!
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I just want to tell you all that we located the problem with the car. It was wiring harness. Isolation was cracked and fell of the wires so some 4-5 wires had conection. It was just above the first cilinder. Thanks and regards Mario

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Good to know you fixed the problem Mario.
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