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'73 450SL, '83 300CD, '01 E320 4matic
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Discussion Starter #1 (Edited)
Well, I've had this car on the road for about 3 weeks now, and I've managed to put about 1500 miles on it. I love it!:thumbsup:

I've got the thing pretty well ironed out as far as the problems I've been having. The biggest thing I've noticed is that it gets really decent gas mileage. I checked on the government website, and I think they are on crack. The car (I noticed this with my 560SEL, too) is listed as a compact car, and is listed as a gas guzzler. It was rated for 15 city, 17 highway. Does anyone actually get these numbers? Mine has gotten 19mpg at the worst, and I've been averaging 21.8 mpg the last two tanks- (25%city/75%hwy).

This morning I went ahead and installed felt strips on the bottoms of the door panels to quiet down the creaks and groans. Whoever came up with this 'fix' gets a thumbs up. The interior is virtually silent now.

Yesterday, I replaced all of the ignition wires (wow are they expensive for this car) and put new plugs in it. The plug wires were pretty whipped, but the plugs still looked nearly new. I changed them anyway, since I had already bought them. I also replaced the oil with Mobil 1 synthetic, and the engine runs much more quietly, and is considerably smoother. I expect this change to improve the fuel economy a little bit too, as the bad plug wires were causing misfiring and whatnot under load at times, particularly in the rain.

So that's all the good.

The bad is:

I still have not ironed out the idle surge problem I've been having. In park, when the engine warms up to operating temperature, it begins surging, between about 900 rpms and a stall. It's pretty severe. It does not do it in drive, with the engine loaded. It's perfectly fine on the road, this only occurs in neutral or park. In 'D' it runs at probably 700RPMs and smooth as glass.

I have checked for vacuum leaks, I've even gone so far as to disconnect every vacuum line and plug the ports. I even disconnected the line to the brake booster and plugged that. No change. I then put some small hose clamps on the ICV boot, since I thought that leaked, no change. This problem is driving me crazy.

I have a creaking/clunking noise in the front end which I suspect from everything I've read on here, and checked out myself underneath the car to be the guide rod mounts. I can hardly wait to tackle that job. I've already ordered a spring compressor that's suggested specifically for MB's.

My one and only other gripe is the car seems to wander. I have gone through all of the service records and discovered that this car has had many, MANY alignments, all at MB dealers and independent MB garages throughout it's life. All or many of the front end components have been replaced within about the last 10K miles. Is this normal? It certainly needs another one. It doesnt pull hard in any direction, it's as if it's not cambered enough, or both wheels are not towed in enough... it just wanders some.

The sunroof also works screwed up, but I have not looked into that yet.

All in all, I love the car and look forward to the continued projects.

Any suggestion about the idle thing would be awesome though.

Aaron-
 

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'82 Euro 500SEL, '85 Euro 500SEC AMG WB Cabriolet,'86 Euro 500SEC RUF
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9,487 Posts
I have a 1984 380SE and I get consistently 25 MPG on the road and about 19 MPG in town.
Your Idle surging may be the Idle control Unit. It can be found between the false firewall and the firewall right of center. it is approx. 1 1/2 " thick and about 5" wide and about 6" tall. While idleing, rap on the case with a screwdriver handle and see if it causes the idle to change or the car to die. If so this is your culprit. Does it die sometimes at lights or just after start up? Again the Idle Control Unit may be the culprit. Also check yout OVP in the fuse box(Relay with the fuse on top).
 

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'73 450SL, '83 300CD, '01 E320 4matic
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2,446 Posts
Discussion Starter #3
I am not finding the idle control unit. Or maybe I am, and it's not the problem. There are a few large modules plugged in. I have two problems.

They are not the size that's described. They are both smaller. And they are both slightly left of center (in other words toward the driver side).

The schematics I have on the CD manual do not list an idle control unit for the 6 cylinder engine, either. 420 and 560 are listed, not 300. Does the 300 have the idle control unit?


Tapping on the modules I found does not cause any changes. I'm not sure what either of the modules are for. The OVP relay does not have a blown fuse, I checked it again to be safe, but I also checked when I got the car.

Does anyone with the 6 have a picture or can you tell me for sure if this has the idle control module, and if so, which part is it, specifically? I just can't figure it out.

Aaron-
 

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'73 450SL, '83 300CD, '01 E320 4matic
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2,446 Posts
Discussion Starter #4
I forgot to answer one other thing. It never stalls at intersections. It runs well in gear. It only surges at an idle with the transmission in park or neutral.

When you go to start it, it does seem to occasionally fire once and stall, this isnt regular. I usually give it a little gas when starting, which is just a habit of mine, and is probably not required for this car. I'm used to doing it with my diesel benz, and the fleet of ancient carburetor-fed cars I have.

The car does start a little on the hard side, especially warm. I've honestly never come across a German car that did not seem to require more cranking time than an American car. So I can't say it's a problem. Maybe it is, but it's not annoying. It does not require prolonged cranking, it always starts just fine, just a little longer than many other cars. My buddy has had a number of Audis, and they all crank about the same amount of time. I think it's a Bosch fuel injection thing.
 

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R129 SL 500 97, W124 E320 Coupé 96, W124 300E twin turbo 90, W126 300 SE 91, Ford Capri 2.8i 84
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249 Posts
My one and only other gripe is the car seems to wander. I have gone through all of the service records and discovered that this car has had many, MANY alignments, all at MB dealers and independent MB garages throughout it's life. All or many of the front end components have been replaced within about the last 10K miles. Is this normal? It certainly needs another one. It doesnt pull hard in any direction, it's as if it's not cambered enough, or both wheels are not towed in enough... it just wanders some.
The E-class owner's bible (Bentley Publishers) says:

"When setting front end alignment, a spreader bar must be used when adjusting the toe. This is a spring-loaded bar that forces the front wheels apart with 90-110Nm (66-81 ft-lb) of force. The use of the spreader bar allows the alignment to duplicate driving conditions by preloading the rubber bushings in the suspension. The use of the spreader bar is the only way to get an accurate front end alignment." [my bold]
 

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1991 Mercedes Benz 300SE
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10 Posts
Location of Idle control UNit

Hi, I have a 91 300SE, I6 cyl. The idle control unit is located under your air filter housing in the engine compartment. You would have to take off the four nuts, holding down the air filter cover. Remove cover and filter. I beleive there are a couple of nuts around the bottom edges holding the lower part of the air filter housing in place. Remove those, and then you should be able to lift up on the entire air filter casing. The idle control unit can then be seen. It is a silver unit, with two , Id say 3/4 inch rubber hoses and one electrical plug on it. The hoses on mine were cracked, allowing outside air to enter the engine, causing it to rev up and down.
 

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2003 ML350
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180 Posts
Akimball,
At the time DOT classified cars these MBs were sort of mid-size compare to the monsters Ford and GM were putting out. As for the gas mileage I get the same 19 and 25 for long distance hwy. One in good condition in these price ranges is a definit steal compare to aluminum cans you get now a days. Have fun working on it.
 
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