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Old 11-11-2003, 09:16 AM
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1988 300E stalling: "steering angle sensor"?

I have read numerous threads about intermittent stalling in this era/model Mercedes, because my
1988 300E is doing it. Pattern: Car starts ok, but a block or two from the house, it starts idling rough and
quits. It does this about once a month. More often in summer than in winter. (this has been going on for about two years.) Sometimes there is a brief surge before it quits, if I have
placed it in neutral. I have it at the shop right now.

A mechanic with about 30 years of experience with MB says he thinks it is the "steering angle
sensor" I have not seen this in any of the threads.

1. What is the steering angle sensor?

2. Does this have a chance of being the problem more than the oft-cited OVPR, fuel pump relay,
idle position sensor, idle control valve, or vacuum hoses?

Any help would be appreciated.
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Old 11-11-2003, 09:28 AM
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BTW, additional information on the 1988 300E:
1. 60k miles
2. 60k mile service completed, did not solve problem
3. oxygen sensor replaced, did not solve problem
4. Distributor cap replaced, did not solve problem.
4. I ran 3 bottles of gumout throught it; it runs better but did not solve problem.
5. The Check Engine light comes on just before it quits.
6. Sometimes the ABS light comes on at odd intervals although not connected in time with the stalling.
7. When it stalls, it does it usually several starts in a row then is fine.
8. Usually it stalls during transition to idle or at idle, although a couple of times it occurred at low speed
and ran rough.
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Old 11-11-2003, 11:57 AM
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Location: Richmond, BC
Posts: 374
Try to clean up the idle control valve and make sure all vacuum is connected well. Then, change the OVP. My 190E stalling problem was the same as you and just solved about 2 weeks ago.
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Old 11-11-2003, 01:00 PM
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OK. I'm going to have that done. Also the guy wants to replace the crank angle sensor. He says that has
been a problem in his experience with this model. Thanks for the reply.
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Old 11-11-2003, 08:11 PM
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Location: Evansville WI
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I kinda figured he meant crank angle sensor. Actually it doesn't have a steering angle sensor OR a crank angle sensor, it's just a TDC sensor. I don't think it's gonna fix anything, probably just end up with the timing being off. Try the OVP.

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Old 11-12-2003, 12:31 PM
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Location: Mass
Posts: 1,127
Consider a marginal fuel pump relay.
1986 300E 5-Speed 240k mi.
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Old 11-12-2003, 05:06 PM
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Gilly and csnow:

Thanks for the messages. I tried to call the shop when I got your message to tell them to hold off
on the crank angle sensor (because of Gilly's comment) but it was too late. They had already done it, had cleaned the idle valve, and replaced the OVP.

This afternoon I got a call from the shop. The guy who did the work took the car out for a test drive
and it started spitting and bucking and misfiring, which it was most definitely not doing before I
took it in. It made me think about Gilly's comment about the timing. Now he wants to change the oxygen sensor. I told them we had changed the oxygen sensor two years ago. Then he tells me there are two of them.

I checked with another mechanic; he said there is only one oxygen sensor in the '88 models.

I'm getting a very bad feeling about this ... Any suggestions?

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Old 11-12-2003, 05:13 PM
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I've been wrong before, but I'm only aware of one O2 sensor for your model. The same one is listed for 1986-89.
1986 300E 5-Speed 240k mi.
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Old 11-12-2003, 07:21 PM
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Boy, real nightmare now.....
Um, my feeling on the timing issue, in general I feel that if it is "capable" of running OK, but later on during a test drive it starts acting up, doesn't really make me feel that they actually harmed anything by replacing the sensor. As long as they were careful to not move the TDC sensor barcket AT ALL, the timing should be close enough. It's not the kind of thing you mess with, takes a dial indicator down the #1 plug hole to get this basic timing set correctly, real precise work.
Only 1 O2 sensor on this car, they added the second sensor way later, mid 90's.

I hate to berate a mechanic, it just doesn't sound like they know their way around a MB, and then using all the wrong terms, such as referring to the TDC sensor as a crank angle sensor (a crank angle sensor keeps track of the entire rotation, the TDC sensor is rather archaeic (sp?) and only senses when #1 cylinder is at TDC (top dead center). The newer engines use a crank angle sensor.
And also referring to a second O2 sensor......
Also the problem doesn't seem like a bad O2 sensor would cause this problem to me.
Probably the best starting place is to get some testing equipment set up on it and then get it in the failed state. What would come to mind first would be a fuel pressure gauge (the kind where the gauge dial can be observed while driving, usually it rests on the outside of the windshield), and various voltage or amperage readings can also be monitored, such as the EHA amperage, the fuel pump amperage, or the engine control module supply voltage. Not all at once of course, but this is a better approach than just driving it, having it fail, and then just saying "Huh, that didn't fix it, what should I replace next?"

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Old 11-14-2003, 04:49 PM
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Gilly, csnow et al.:

Here's the denouement. Part of the problem is that this dealer puts a service manager in between the
customer and the mechanic. It was the service manager who was harried and not very good who was
confused about the steering angle sensor and the number of oxygen sensors. It turns out, however, that
the mechanic was not that hot either. But at least he was honest.

to recap:

1. Monday an authorized Mercedes dealer/repair shop picked up the car.
2. Tuesday the service manager told me our stalling problem was the "steering angle sensor".
3. When I insisted on talking to the mechanic, the mechanic said it was the crank angle sensor.
(Despite replies to my thread, he insists it is a crank angle sensor, not a TDC. He says it fires the
plugs, so it is not just a TDC sensor.)
4. The mechanic and I agree that he will replace the crank angle sensor, the OVP, check the vacuum
hoses, and clean the idle control valve.
5. Wednesday the service manager calls and tells me the car runs rough on the road and the mechanic
wants to swap out the oxygen sensor. We replaced the oxygen sensor two years ago, so I insist on
talking to the mechanic again.
6. When I finally reach the mechanic, he says that in fact the car runs well, the service manager
didn't get the right message, but the idle is low and rough.
He says that he recommends the oxygen sensor because no signal is coming from it. I repeated to him
that the oxgen sensor was replaced two years ago and is unlikely to be bad.
7. The mechanic calls me on Thursday to report that he checked the actual output of the sensor and
found that indeed it works (!) but that the computer is not using the information. He says that the next
step woudl be replacement of the computer.
8. The mechanic replaced a resistor somewhere that caused the idle to rise from 500 to 700 and
told me to see if that helps because the computer costs about 1200 bucks.

Conclusion: This dealer did about a kilobuck of useless work.

Anybody know where I can get a good used computer? part KEInjector Control 0085451632?
I won't print a verbalization of my feelings about his whole process, I will leave them to your imagination.

Conclusion: This was a frustrating experience.
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Old 11-14-2003, 05:11 PM
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Join Date: Sep 2001
Location: Austin, TX
Posts: 563
It sounds like this guy is throwing parts at it and I would find it hard to swallow a $1200 part in that scenario. I would think about taking it to an Independent that specializes in Mercedes. They probably work on M103s all the time.

Where are you located?
Mike Heath
1988 560SL Black/Palomino
1988 300SEL Black Pearl/Burgandy
1984 500SEC Anthracite Grey/Palomino
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Old 12-15-2003, 04:45 PM
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We got the car back and drove it for one month during which it ran well, then suddenly started doing the same thing, only worse.

Does anyone know a highly skilled independent Mercedes mechanic in Western Pennsylvania?
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Old 12-15-2003, 05:04 PM
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It sounds like you need to do what I should have done 4 years ago, sell that moneypit!
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Old 12-18-2003, 01:41 AM
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Join Date: Jul 2003
Posts: 90
Please check the Air flow meter Sensor or Potentiometer

Mr. Psr7, try with the Potentiometer. Use the Multivoltmeter and contact the Positive led -Red- with the Pin 2 and black lead with the ground. Star the engine at idle in park.

You have to read 800 Milivots +/- 250 MV. If not, try to rotate the Pot litlle bit until you get close to 800 MV.

The new Pot is $71.00

Many threadid about it.

Mario Farias
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