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1990 Mercedes 300E
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66 Posts
Discussion Starter #1
Hi All,
I'm new here, not sure if I have the right place for this question, but any help would be appreciated.
I have a 1990 300e with sluggish acceleration, and a bit of a rough start, I've been reading that cleaning the MAF sensor might help. I'm not sure how to go about that, the diy sections don't show my particular engine (at least that I can find, I am new at this). My sensor seams to be mounted on top of the throttle body, and attached to all the fuel lines as well. Is there any way to clean this, let me rephrase, an easy way to clean this. Seams to me that I would have to remove a lot of stuff to get to the sensor.
Any help would be greatly appreciated!!! Thanks in advance.

WillEd
1990 MB 300E
 

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Premium Member
About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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A 1990 300E (that's the sedan) has the M103 engine. That engine doesn't have a MAF sensor.
 

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1990 Mercedes 300E
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66 Posts
Discussion Starter #3
A 1990 300E (that's the sedan) has the M103 engine. That engine doesn't have a MAF sensor.
oh...ok, i guess that answers that question. What about the air flow meter siting on top of the throttle body, can that be cleaned (lots of gunk lining the walls) or does it not need to be cleaned?
Any other thoughts on the sluggish acceleration and rough starts?
Thanks,
WillEd
1990 300E
 

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2008 E350 4M, 2016 Audi Allroad, 2019 Audi Q5
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I would completely remove it. It serves for multiple functions. First of all, the rubber boot that it sits on can have cracks out of sight which will cause rough idling and a number of other issues...Then you can clean everything out with carb cleaner, reposition the throttle plate, replace the fuel distributor seal that tends to leak with age, make sure the plate is not binding and moves freely and smoothly etc...

Definitely worth the hour to do it.
 

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1990 Mercedes 300E
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66 Posts
Discussion Starter #5
I would completely remove it. It serves for multiple functions. First of all, the rubber boot that it sits on can have cracks out of sight which will cause rough idling and a number of other issues...Then you can clean everything out with carb cleaner, reposition the throttle plate, replace the fuel distributor seal that tends to leak with age, make sure the plate is not binding and moves freely and smoothly etc...

Definitely worth the hour to do it.

Thanks for the advice. This might be a stupid question, but I don't have a lot of experience. Do I need to remove all the fuel lines from the fuel distributor and injectors, and what is the rubber boot you referred to (what's it called to look it up)? Also, is there anything special I need to know putting it back together, I've never worked on the fuel system?

Thanks for all the help!

Willed
1990 300E
 

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2008 E350 4M, 2016 Audi Allroad, 2019 Audi Q5
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No special tools. Most are all 10mm. Fuel lines can just be unplugged at the distributor. Not difficult. The rubber boot sits under the throttle plate. Since it is rubber and probably over 20 years old, it can go hard and crack.
 

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1990 Mercedes 300E
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Discussion Starter #7
No special tools. Most are all 10mm. Fuel lines can just be unplugged at the distributor. Not difficult. The rubber boot sits under the throttle plate. Since it is rubber and probably over 20 years old, it can go hard and crack.
Thanks for the help! Anything else I should replace while I'm digging around in there? Do you know what the rubber boot is called under the throttle plate to help look up the part?
Thanks again for the help, can't begin to tell you how much I appreciate it.
 

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300 CE 24V Sportline
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.Anything else I should replace while I'm digging around in there?.
Yes:

1. Check and replace as necessary any vacuum hoses and their boots, including those for the Idle Control Valve.

2. Unplug and clean any electrical connectors using a good quality switch/contact cleaner. Check all wiring.

3. Look for anything damaged, dirty or generally old looking. Clean/replace as necessary.

All these suggestions are low cost options and should not be overlooked.

Bon courage.

RayH
 

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1993 300e 2.8
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129 Posts
I had the same issues and it ended up being the #1 coil. Wasted money on a new MAF. A $40 coil solved all the sluggish issues.
 

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1990 Mercedes 300E
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Discussion Starter #10
I had the same issues and it ended up being the #1 coil. Wasted money on a new MAF. A $40 coil solved all the sluggish issues.
#1 coil? Is that the ignition coil?
Thanks
 

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About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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Will, RickDean's 93 has a different engine and different fuel system and different ignition system.
 

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86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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Will,

Use the search function of this site and look up "air/fuel ratio adjustment". By reading all the post on this subject you'll learn quite a bit. You need some basic tools, multi-meter and minimal DYI skills.

If you have no idea of the past service history on the car, it would be good to start a base line of maintenance items. Full tune up, including correct spark plugs, new cap, rotor, wires, change all fluids including the transmission, change all filters and so on.

This is a wonderful forum and contains a wealth of information about your car. By using the search function, you'll learn that there isn't anything that comes up with your car that hasn't already occurred with someone else. These cars were sold world wide for 9+ years and there are plenty out there.

Good Luck and welcome

Jayare
 

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1990 Mercedes 300E
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Discussion Starter #14
Will,

Use the search function of this site and look up "air/fuel ratio adjustment". By reading all the post on this subject you'll learn quite a bit. You need some basic tools, multi-meter and minimal DYI skills.

If you have no idea of the past service history on the car, it would be good to start a base line of maintenance items. Full tune up, including correct spark plugs, new cap, rotor, wires, change all fluids including the transmission, change all filters and so on.

This is a wonderful forum and contains a wealth of information about your car. By using the search function, you'll learn that there isn't anything that comes up with your car that hasn't already occurred with someone else. These cars were sold world wide for 9+ years and there are plenty out there.

Good Luck and welcome

Jayare
Thanks Jayare, I appreciate the warm welcome!
 
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