kinda new to the forum and wondering if anyone has come across this problem?
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From: Calgary, Alberta
1993 E300 2.8l
kinda new to the forum and wondering if anyone has come across this problem?
Hi, i have a 993 e300 with the 2.8l.. currently i'm having problems with backfire's ( in exhaust) due to rich condition and hesitation during acceleration under load starting from a stop. Car starts and idle's normal and I find during W.O.T it seems like it's running with 5 cylinders (very jerky at this point, kinda feeling like a possible secondary igntion problem) till 4500 rpm+ when finally the last cylinder kicks in.. When this problem started i swapped out spark plugs and sprayed down ign wires with soap and water but could not confirm anything. I have removed my air pump and bypassed it due to it being on it's last legs nearly seizing before this problem. i'm reinstalling a new airpump in the next week cause i noticed a great drop in fuel economy. I know these vehicles are known for the wiring harness which sucks cause i've noticed the condition of my wires and fear i may have some work ahead of me. I guess i'm just wondering if anyone has experieced something like this condition and have any ideas? Also wondering if the Air flow sensor's or coolant temp sensor's are known to have issue's on these cars, keeping in mind it is 15 years old??? Anyhow any advice is greatly accepted! Thanks in advance..
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Joined: Dec 2006
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From: Bellevue, NE
1995 E320 SE, 162,000 Miles (Sold) 2007 CLK350 Cabriolet 2014 ML550
Hi, i have a '93 e300 with the 2.8l.. currently i'm having problems with backfire's ( in exhaust) due to rich condition and hesitation during acceleration under load starting from a stop. Car starts and idle's normal and I find during W.O.T it seems like it's running with 5 cylinders (very jerky at this point, kinda feeling like a possible secondary igntion problem) till 4500 rpm+ when finally the last cylinder kicks in.. When this problem started i swapped out spark plugs and sprayed down ign wires with soap and water but could not confirm anything. I have removed my air pump and bypassed it due to it being on it's last legs nearly seizing before this problem. i'm reinstalling a new airpump in the next week cause i noticed a great drop in fuel economy. I know these vehicles are known for the wiring harness which sucks cause i've noticed the condition of my wires and fear i may have some work ahead of me. I guess i'm just wondering if anyone has experieced something like this condition and have any ideas? Also wondering if the Air flow sensor's or coolant temp sensor's are known to have issue's on these cars, keeping in mind it is 15 years old??? Anyhow any advice is greatly accepted! Thanks in advance..
Last edited by shdoug; Mar 11, 2008 at 09:38 PM.
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From: British Columbia, Canada
1987 560SL
You say your wires are bad?
What mileage have you got on that car? Expect problems around 120K miles.
Just poking around in there, changing other things, can cause wires in bad shape to cause problems.
Someone else on here is bound to know more than I do, but good luck.
What mileage have you got on that car? Expect problems around 120K miles.
Just poking around in there, changing other things, can cause wires in bad shape to cause problems.
Someone else on here is bound to know more than I do, but good luck.
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From: Calgary, Alberta
1993 E300 2.8l
I have roughly around 120 miles (48k miles on speedo now and 130k km on old speedo) i can Understand how timing may be off but i find it hard to believe since the engine is chain driven..? I am going into work on the weekend and i was planning on checking compression to eliminate the fact it could be a mechanical issue. I just cant figure how a chain would skip teeth, i can understand how chain would gain slack over so many km/miles but i doubt it would be able to get that much play to skip teeth??. Regardless at last resort i will definatly check timing and let you guys know.. Another thought i had was since this engine is electronically controled is that since i took out my Airpump, by some far fetched reason since it is cold out and the outside air temp is lower, this may effect the fuel delivery??, but i cant see it being so rich that the air/fuel mixture would not ignite and get pushed into the exhaust to create a backfire? Just throwing some idea's out? I know VW's very well but MB is very foriegn to me...
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From: Bellevue, NE
1995 E320 SE, 162,000 Miles (Sold) 2007 CLK350 Cabriolet 2014 ML550
If the engine has been poorly maintained (oil not changed often enough) the timing chain can become loose and skip, though it's not common with these cars. If fact, I've never heard of it on an M104. That's just what the symptoms point to.
The cam could be out of time and still give a good compression test at cranking speed. If the cam is slightly retarded it will idle fine but with somewhat lower vacuum. Under load it will buck and pop, and when the cam advances by the variable valve timing, it will shape up immediately though still not putting out full power.
It could be something else but I can't think what. Why did you put soap and water on the wires? Any CEL codes?
The cam could be out of time and still give a good compression test at cranking speed. If the cam is slightly retarded it will idle fine but with somewhat lower vacuum. Under load it will buck and pop, and when the cam advances by the variable valve timing, it will shape up immediately though still not putting out full power.
It could be something else but I can't think what. Why did you put soap and water on the wires? Any CEL codes?
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From: Calgary, Alberta
1993 E300 2.8l
Being a Autmotive tech for VW, soap and water sprayed on Ign wires will most of the time always point out a misfire, even if the vehicle is operating normally at the time (you will see electrical arc's, and the engine will stumble if a wire issue). My vehicle has been kept up with normal service intervals if not more then are required 
.. I most definatly dont dispute the fact about timing and it most definatly is in my mind a s a possible.. i was just looking for a simple way of solving this problem is there is one because A) i hate working on my own car (lazy) and B) no offense to MB, they suck to work on and they keep there spec's/secrets to themselves which makes life tough when you dont have access to the info you need if you dont work at a dealer! 
Btw, knowing these vehicles are obd 1 and dont have a obd 2 port? do you have any info on checking for codes, i know thay have the pin out box by the battery, but for the values of the pin and what they are is far beyond any info i can find...
.. I most definatly dont dispute the fact about timing and it most definatly is in my mind a s a possible.. i was just looking for a simple way of solving this problem is there is one because A) i hate working on my own car (lazy) and B) no offense to MB, they suck to work on and they keep there spec's/secrets to themselves which makes life tough when you dont have access to the info you need if you dont work at a dealer! Btw, knowing these vehicles are obd 1 and dont have a obd 2 port? do you have any info on checking for codes, i know thay have the pin out box by the battery, but for the values of the pin and what they are is far beyond any info i can find...
Last edited by E3002.8; Mar 11, 2008 at 10:45 PM.
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From: Bellevue, NE
1995 E320 SE, 162,000 Miles (Sold) 2007 CLK350 Cabriolet 2014 ML550
Right on! I understand about them being hard to work on and I'm lazy when it comes to that as well. Thanks for the tip about the soap. I didn't know that. I take it nothing changed when you soaped it?
You've owned it since new? I just figured maybe the previous owner let the oil changes slip.
Here's the link to the CEL codes and procedure. https://mbworld.org/forums/e-class-w124/119377-check-engine-light.html
I sure wouldn't suspect a timing chain issue with only 120,000 miles and proper oil changes. Is it possible the tensioner adjusting bolt (left outside of block) loosened up?
You've owned it since new? I just figured maybe the previous owner let the oil changes slip.
Here's the link to the CEL codes and procedure. https://mbworld.org/forums/e-class-w124/119377-check-engine-light.html
I sure wouldn't suspect a timing chain issue with only 120,000 miles and proper oil changes. Is it possible the tensioner adjusting bolt (left outside of block) loosened up?
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From: Cambridge, Ontario
95 E320 Coupe, Diesel Golf
I used to have the same backfiring problem even after I changed the E-harness, but the wire set solved the problem, while your are there go ahead and change the plugs as well..
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From: Calgary, Alberta
1993 E300 2.8l
Thanks for the answers guys, I was thinking of changing the wires anyhow due to the age, i will let you know how it goes, may take a couple days due to ordering of parts for these older cars...
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From: Melbourne
2007 GL500, 2007 E280
