My 87 560 SL failed NJ emissions inspection (CO & HC). In a flurry of potential overkill, I replaced all of the injectors and the oxygen sensor, which was badly fouled with carbon. Unfortunately, I have no idea what the previous owner may have done to the mixture adjustment, but can refer to two symptoms:

1. When the car accelerates hard it sends out quite a bit of smoke.

2. Gas mileage, from what I can see, is about 12 mpg.

To me, this sounds like it may be running rich, but I have no way of telling, and am reluctant to run it through inspection again without making some effort to ensure that the mixture is correct. Are there any suggestions besides visiting my neighborhood M-B dealer and taking out a mortgage on my house at the same time?

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M. Sandler

1986 560SEC: 150,000 miles, runs great, but I've got to sell it (too many cars for one man)
1987 560SL: 122,000 miles, used to run poorly, now (thanks to forum), runs great!
1997 GMC Jimmy: Turned out to be a turkey.
1989 T-Bird Super Coupe: 150,000 miles, still runs great. Ford got it right.

Sounds rich.

Any Indie shop should have an analyzer and should be able to dial you in for much less than the dealer. Will probably take about 1/2 hour to dial it in, it needs to be checked at both high idle (2500 RPM) and low idle (600-800 RPM).

The 12 MPG, is that city, highway or combined? On the 560SEL I get a shade over 13MPG city and 19+MPG highway (extended trip).

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

That mileage was almost all highway, which prompted the question. Also, pulled a plug this morning and found a lot of black carbon deposits, typical or running way too rich. I'll try to find an indie shop to dial in the mixture setting. Thanks for the advice.

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M. Sandler

1986 560SEC: 150,000 miles, runs great, but I've got to sell it (too many cars for one man)
1987 560SL: 122,000 miles, used to run poorly, now (thanks to forum), runs great!
1997 GMC Jimmy: Turned out to be a turkey.
1989 T-Bird Super Coupe: 150,000 miles, still runs great. Ford got it right.

The problem is that you can't run rich and "run". The system is self regulating so you aren't.

With a new O2 sensor its possible to correct a system that someone just overwhelmed with ignorance but your car will not run rich in closed loop. To get to the bottom of this you must establish closed loop. Check the archives for more on the concept and look at the DIY article evaluating engine controls to see easy methods for analysis.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Thanks, Steve. I'll read the DIY article and also look for an indie shop. Thanks to all for the help.

__________________
M. Sandler

1986 560SEC: 150,000 miles, runs great, but I've got to sell it (too many cars for one man)
1987 560SL: 122,000 miles, used to run poorly, now (thanks to forum), runs great!
1997 GMC Jimmy: Turned out to be a turkey.
1989 T-Bird Super Coupe: 150,000 miles, still runs great. Ford got it right.