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  #1  
Old 05-28-2002, 12:00 AM
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Join Date: Apr 2002
Location: Canada
Posts: 48
Please help me with 450 SEL

OK I figured it out. I know nothing.

My car starts poorly (need to push the gas) and idles either high (1200 rpm) or idles too low (500 rpm) or idles perfectlt at 700 rpm.

Ive heard mention of the OVP but cant locate on my car.

It seems that when the climate control is working properly (cold air center) it idles differently than when it is not working (warm air sides and floor no center).

Otherwise the car runs great just starting and idling are rough. There doesn't seem to be any change re: engine temp. The car either starts a bit rough and idles great. Or starts rough and idles high or low. Stays that way (whichever way it happened to start).

Please help....

Mike
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1976 Mercedes 450 SEL (170K Miles)
1999 Nissan Altima GXE (45,000 km)
1986 Ford Bronco II 4x4
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  #2  
Old 05-28-2002, 12:40 AM
Holson Adi's Avatar
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Join Date: Jul 2001
Location: Boston, MA
Posts: 2,561
Have you checked the throttle linkage?

I'd think that on a 450SEL the idle speed would be mechanical. It does have fuel injection right?

Have you checked these things BTW?
Air filter, and fuel filters?

Maybe it's a spark plug problem?

I'm sorry I can't be of much help. However don't worry help will be on its way
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2008 BMW 335i Coupe
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  #3  
Old 05-28-2002, 01:50 AM
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Yes to Fuel injection

It is fuel injected. There is a fuel air mixture screw in front of the fuel distribution system. But thats it.

The plugs are a recent change.

Thanks for the reply...

I ordered a cd manual off of ebay but havent received yet.
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1976 Mercedes 450 SEL (170K Miles)
1999 Nissan Altima GXE (45,000 km)
1986 Ford Bronco II 4x4
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  #4  
Old 05-28-2002, 03:35 AM
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Join Date: Jul 2000
Posts: 72
Mike,
Since you are talking about a fuel distributor I am assuming your car has CIS and not D-Jet. Does it idles better or worse when the Climate Control works? This could lead to a vaccum issue.
Check the sensor plate in the air flow meter to see if it's moving freely. I suggest you replace the spark plug wires also, I had an issue in my 1980 450SEL where it would idle rough after sitting for a few days and changing the wires made a big difference.
Your car should have a vaccum valve to maintain idle when the compressor kicks in. Vaccum issues on these cars can have very strange symptoms so make sure all your vaccum systems work properly. Let me know how it goes.
Regards,
Joe Brasileiro
1980 450SEL
1987 Jaguar XJ6
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  #5  
Old 05-28-2002, 11:06 AM
PaulC
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I seem to recall that 1976 was the first year for CIS.
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  #6  
Old 05-30-2002, 01:25 AM
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Join Date: Apr 2002
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New Development

OK

The actual compressor button doesnt do anything. I do get cold air through the center vents though. So I have noticed this.

When the center vents are working the car idles normally. When they arent working the car ides too low..

Unrelated (I think) is reluctant start (need to push accelerator)

Thanks for the help so far.
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1976 Mercedes 450 SEL (170K Miles)
1999 Nissan Altima GXE (45,000 km)
1986 Ford Bronco II 4x4
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  #7  
Old 05-30-2002, 02:40 AM
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Join Date: Jul 2000
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Mike,
Very interesting....
I suspect a vaccum problem, what is the condition of your servo? Has it been replaced recently? If not and in order to eliminate a vaccum leak in the climate control system as the cause:
1) Look near your break booster for the green/black vaccum hose that goes into the car. That is the main Climate Control vaccum line.
2) Unplug it from the rubber splitter and cap the splitter, by doing this there is no vaccum going into the Climate Control system and no vaccum loss from the engine.
3) Start the car and see what happens to your idle.
4) If idles is ok then there is definetely a vaccum leak afecting the idle.
5) You will then have to check where the leak is. Let's try the above first.
One more question: You mentioned the compressor switch does not do anything. Is your cpmpressor cycling at all? There is an idle compensation switch that kicks in when the compressor is on. It is located at the firewall near the servo next to the outside air temp sensor plug and it also may be defective.
Good luck,
Regards,
Joe Brasileiro
1980 450SEL
1987 Jaguar XJ6
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