About 2 months ago I replaced the oxygen sensor in my 1987 560 SEC with a 3 wire Denso universal a month after that the oxygen sensor light in the dash would come on and the engine would get bogged down once in a while, and slowly the frequency of this occurance increased so yesterday I bought a 1 wire Bosch o2 sensor to see if this would resolve the problem, then i took it on a test drive and it was the same if not worse. I am not sure what to do, any help would be great.

Thanks
Josh

Your problem is not related to the O2 sensor. The solution may vary.
I'd first check for a vacuum leak and all of the spark plugs and their wires as well.

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I have recently replaced plugs, wires, fuel filter, air filter, and distributer cap and rotor, I dont see any obvious porblems with the vacuum lines, but ill have to take a closer look.

why would you install a 1 wire O2 sensor? that would be all the more likely to load up..

What plugs are you running?

Where does your economy gauge sit while idling in gear?

Jonathan

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Jonathan Hodgman
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I got the 1 wire o2sensor because it was much cheaper just diagnostics.

I think the plugs are bosch, but i will double check on that

the economy gauge is pinned to the left at idle unless the AC is on then it is about a 1mm off the pin.

Well, I'd get the other O2 back in..

Did you ever ohm out your wires?

Have you ever set your CO? How old are your fuel pumps? Have you checked your pressures?

Jonathan

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Jonathan Hodgman
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Enthusiast Service, Restoration & Tuning.
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Located in the Atlanta area
Specializing in all pre and post merger AMG's including Hammers and DOHC M117 engines.
Mercedes Repair Atlanta

Plugs are NGK BP5ES
Wires are Bremi

I replaced one of the fuel pumps because it developed a leak

I have no idea what CO is

also when the 02 light comes on the economy gauge jumps like 3/8in towards the red durring idle.

How many miles are on the engine? How does it idle? Steady? What do you mean Bogged down? Does it ever die?

First, make sure you have the correct O2 sensor for your car. My Euro 500 uses a one wire Bosch but I don’t know the 560.

In the words of the local dealers shop foreman “It could be a lot of things. We usually have to change a lot of parts so it cost s a lot of money and people don’t want to pay”. I said “that is me exactly” and he took a pass on my (Gray Market) car.

I fixed everything over time, by myself, but it took me a long time because I am a total amateur and I did have to replace a lot of parts and they were rather expensive but the results are great. Good luck.

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Steve
1985 Mercedes 500SL Euro (Gray market)
1995 BMW 520i Euro (Gray market)
1992 BMW 525it Wagon
1994 Honda Del Sol Si

well it was running great for the last few days, but today it was worse than ever, the oxygen sensor light was almost always on and it stalled on me once going about 10mph.

I just dont know what else to change, what would be the next few things i should replace to get it running right?

car has 114,000mi
idle is nice and steady at about 600-700rpms untill the o2light comes on then it will drop down and then jump up to 1000rpms.

The idle jumping could be your idle control valve and controller. Your dying problem could be your ignition control module in the left fender well. Does it die when cold or hot? Does it run okay when you start it and develop the problems after you drive it awhile? Next time it dies feel the temp of the ignition control module. If it's really hot, it could be shot.

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Steve
1985 Mercedes 500SL Euro (Gray market)
1995 BMW 520i Euro (Gray market)
1992 BMW 525it Wagon
1994 Honda Del Sol Si

so far it has only died once on me and it was up to temp and coasting when it happend.

it seems that as soon as the o2 light comes on the performance is much worse, and back to normal as soon as the light goes out. Is that just the car going into open loop?

it's prob in open loop .sounds like you need to lean down the mixture or richen it up.those o2 lights were meant to advise that the mixture was stuck at one end [low numbers=lean high numbers=rich] you will need to adjust 3mm to change the setting back to the correct one.

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