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  #1  
Old 09-23-2003, 06:16 PM
mike690003's Avatar
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Location: Miami,FL
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Anyone had this problem with the M103 motor???

As you all know, my 300E has ate up a lot of $$$ and it is still missing at idle. I have been feverishly attempting to pinpoint the culprit that is causing my 300e to run so rough. I have to suffer while driving in the daytime because if I turn my A/C on, my car will hestiate from the stoplight really badly, to the point of almost stalling. Well what I have come to realize is that it runs really rough only in the hot daytime. This is basically everyday in Miami,FL. When I drive at night the car idles a lot better, it does not miss at idle as much and the hesitation is not as bad. Well I have recently replaced my #5 and #6 fuel injector( the worst ones). I plan on doing the whole set next week,but I do not know if the solution could be a more simple part.

I was wondering if the coolant temperature sensor could have an effect on this weird problem??

Any other suspected culprits??
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1987 mercedes 300E
1995 e320 conversion(hated the 300e grill)
HID/Xenon (D2S)
Keyless Entry
Monochromatic Paint (Custom Blue)
Smoked Tails
Flat Badged (front)
Debadged (rear)
custom "carbon fiber" console
18 inch HP EVO rims
Sold! Now I drive a Monte Carlo SS
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  #2  
Old 09-23-2003, 06:40 PM
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Location: Naperville, Illinois
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Mike,

Sounds like your changed out engines, right? If so, then you need to first look for the obvious things. Rough idle can be a number of things, but I would first check all your vacuum lines. A vacuum leak can cause a rought idle.

In the fuel circuit, you may also want to do functional test on your cold start valve. If the valve is leaking through, you could be running a rich mixture at idle........which could account for the stumble (and would also be reflected in poor fuel consumption).

Depending on age of the car, you may want to also proactively replace some ignition components such as your ignition wiring, including the distributor rotor and cap.

Those are a few things that can be done cost effectively and should help your situation.
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  #3  
Old 09-23-2003, 07:07 PM
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Location: Miami,FL
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Thanks for the reply. Well I have done a lot of things to my car so far. The previous owner must have driven the car without any maintenance. Well I have replaced a long list of parts

-OVP Relay
-Voltage Regulator
-fuel filter
-New Cap
-New Rotor
-New plugs
-New wires
-new vacuum lines
-injector seals
-new radiator
-new thermostat
-new vacuum sensor on top of engine(has 2 vacuum lines coming out of it)
-New fuel sending unit
-Cleaned idle control valve
-new 02 sensor
-fuel mixture was corrected to spec
-cleaned all electrical connections
-new air filter
-replaced #5 and #6 injector
-cleaned throttle plate
-new aux fan
-spent lots of $$$ on Techron
-Spent lots of $$$ on diagnostics


and a few things I cannot remember off hand

My last resort is to take it to the dealer for a diagnostic($200). Well my next project is to replace the other 4 injectors, if that does not solve this problem, I will have to take it to the dealer(the prices are so high!).

I was just hoping that someone had the same problem and traced it down to a simple sensor of hidden vacuum line.

It is very frustrating and I have spent thousands into this car, and it sucks that I still have this problem.

Quote:
you may also want to do functional test on your cold start valve
How do I do this??

Any suggestions???
__________________
1987 mercedes 300E
1995 e320 conversion(hated the 300e grill)
HID/Xenon (D2S)
Keyless Entry
Monochromatic Paint (Custom Blue)
Smoked Tails
Flat Badged (front)
Debadged (rear)
custom "carbon fiber" console
18 inch HP EVO rims
Sold! Now I drive a Monte Carlo SS
http://memimage.cardomain.net/member.../352975_67.jpg
http://memimage.cardomain.net/member.../748335_24.jpg
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  #4  
Old 09-23-2003, 07:33 PM
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Location: Naperville, Illinois
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You must remove the cold start valve. Then with it set to discharge into a container, have someone turn on the ignition. With the ignition on, the fuel pump will pressure up the system, and you should not see any flow out of the cold start valve. If fuel dribbles out, you need to replace the valve. This valve is controlled by a thermoswitch that allows it to pulse for only a few seconds on a cold start. When the engine is warm, the cold start should not operate at all. Cost of a new valve is about $75.

On the topic of vacuum leaks........have you checked the intake seal? As I recall from your last note, it appeared as though you might have changed out the engine recently. If so, and you swapped out the accessories, you may have a vacuum leak at the intake manifold to block interface. You can test this with the car running with a soapy solution.
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  #5  
Old 09-23-2003, 08:18 PM
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Location: SC
Posts: 148
Correction! The fuel pump comes on while cranking and not by having the ignition on by it self. You must jumper I believe (check!) 30 and 87 at the fuel pump relay connector to activate the pump. No fuel should drip from the cold start valve when the pump is energized. On the other hand, while cranking, the cold start valve will spray for a few seconds and then stop. It should not drip fuel out of the nozzle after it sparys.
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  #6  
Old 09-23-2003, 11:14 PM
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What fuel are you using? If you are using rot gut fuel, that may be your problem. Carbureters will take anything, and I have used the cheapest, but injectors don't like cheap fuel. I am not in anyway connected to Chevron nor do I particularly care for the company, but the Techroline really works to keep the injectors and backs of the valves clean.

Peter
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  #7  
Old 09-23-2003, 11:35 PM
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I too have an M103 motor and recently posted an issue here regarding a drop in idle when the A/C was turned on. Here's the thread:

91 300SEL - Idle drops when A/C is on

My problem is very sporadic. I pulled the MAS and used electrical parts cleaner on and around the pins. Things looked a bit dirty and among other things, there is A/C control in this unit. To date, I have not experienced a reoccurrence. By the way - your M103 does not have a MAS. This device replaced the fuel pump relay/klima and a few others on 90 & 91 models like mine.

In another post, M.B.DOC mentioned items that affect idle. They are:

Throttle valve switch, decel switch, hall effect speed sensor; air flow position sensor. Most of these are covered by Steve Brotherton in the thread I pointed too above.

A simple place to start might be the ISC valve(idle speed control) valve. joe p mentioned this in more than one thread. This device controls air feed when the throttle plate is closed. In another post at this site, he suggested a simple way to clean it.

The cold start valve was mentioned earlier in this thread. I notice Mike that you are in DEEP south Florida. Steve Brotherton mentioned in another post some time ago that in x number of years, he's seen but a few failures of this device. The relevance is he too is in Florida and from what I gathered , this device might benefit drivers in REALLY cold places, but not Florida.

Good luck.
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1991 300-SEL - Model 126
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  #8  
Old 09-24-2003, 12:24 AM
MARIO FARIAS's Avatar
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Location: PUERTO LA CRUZ, VENEZUELA
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TO ANY ONE

THANKS GUYS, for this interesting threadid.

I have a similar problem in my 190E, 2.6L, 1989.

I can't get perfect idle.

At morning is hard to start. We don't note the operation of the cold start valve. We messure zero volts in the socket going to the CSV.

We clean the idle valve, test and it works, but It don't increase the RPM when is cold or when the AC start. It does'nt compensate the RPM when the AC start.

The voltage of the line disconected going to the idle valve is the same that the battery (12.70 volts), but when it is connected to the idle valve we read only 1 volts.

Please, From where is coming the additional energy to active the idle valve?

Please, Can anybody to explain the wire operation diagram for the idle valve and cold start valve ?

The car lost 200 RPM when AC start, and 300 RPM when shift from P to Drive.

All the injectors and plug are new. I will try to get vacuum linkage with soapi solution.

Once changed the O2 sensor we get MAS calibration for 50%, using the allen 3 mm and messuring betwen pins 2 and 3 in the test socket.

Thanks

MARIO FARIAS

laprefar@cantv.net
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  #9  
Old 09-24-2003, 01:24 AM
Mike Murrell's Avatar
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Mario:

I do not know if a "perfect" idle is possible in any 14 year old car such as yours, but here's a thread that offers a 50rpm increase that may be of value. It may or may not apply to your vehicle. Look at the words presented by stevebfl:

'87 300E Stalling
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  #10  
Old 09-24-2003, 02:42 AM
N2MBZ
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what type of spark plugs are you running?
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  #11  
Old 09-24-2003, 03:04 PM
mike690003's Avatar
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Location: Miami,FL
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I am running the regular Bosch coppers(H9DC). Well I plan on replacing the injectors to see if this solves my problems.

The main problem I see is that:
-The car will start right up on the FIRST start of the day.
-My car will run fine for the firs 10 minutes of the day.
-After that it starts to miss slightly.
-The idle will fluctuate from 500-600rpm during the missing
- if I turn my A/C on the missing becomes a lot more noticeable.
-After driving for 10 minutes with the A/C on, the car will hesitate very very badly when coming from a traffic light.
-When I stop somewhere and come back to restart my car, it will take 5 seconds to start up, as if it is starved of fuel.
-Then the car has the miss at idle for the rest of the day.

I am lost with this problem.
__________________
1987 mercedes 300E
1995 e320 conversion(hated the 300e grill)
HID/Xenon (D2S)
Keyless Entry
Monochromatic Paint (Custom Blue)
Smoked Tails
Flat Badged (front)
Debadged (rear)
custom "carbon fiber" console
18 inch HP EVO rims
Sold! Now I drive a Monte Carlo SS
http://memimage.cardomain.net/member.../352975_67.jpg
http://memimage.cardomain.net/member.../748335_24.jpg
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  #12  
Old 09-24-2003, 07:25 PM
MARIO FARIAS's Avatar
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Location: PUERTO LA CRUZ, VENEZUELA
Posts: 90
MIKE MURRELL

THANKS MIKE. The STEVEBFL treadid is great even was wroten

two years ago. CONGRATULATIONS STEVE.

Please, any one can send the wiring diagram for this 190E, 2.6L, 1988?

Thanks a lot.



Mario Farias
laprefar@cantv.net
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  #13  
Old 09-24-2003, 08:17 PM
N2MBZ
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Good deal! It's amazing how many people run platinum plugs and complain about a rough idle. How are your motor mounts? they are hydraulic mount and will transfer viberations in stead in absorbing them if they are bad.
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  #14  
Old 09-24-2003, 09:31 PM
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Join Date: Jun 2001
Location: Northern Calif. (Fairfield Area)
Posts: 2,225
I'm still saying that quality of fuel is important on CIS cars. I have a friend with a 420SEL that shook at idle like a dog crappin peach seeds. Turns out his wife is buying her fuel at Costco. After I checked everything according to the MB diagnostic manual, I told him to start adding Techroline treatment to the fuel. He went through about six bottles, and now the car idles quieter than a mouse pissin on cotton. Fuels without the propper additives allow carbon deposits to build on the injectors and the back of the valves. These deposits soak up the injected fuel so the cylinder ends up with a lean misfire. These deposits can cause all kinds of driveability problems. I'm not saying this is the answer, but the possibility has merit.

Good luck,
Peter
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