Setting air/fuel mixture - Mercedes-Benz Forum

 
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post #1 of 3 (permalink) Old 03-11-2009, 08:00 PM Thread Starter
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Setting air/fuel mixture

What would be a good procedure for adjusting the map sensor and the co2 adjustment on the ecu? I'm dealing with a d-jet 4.5.

I've done the basics. Timing and dwell is in check, new plugs, all the sensors test good, Timing chain checks out.
But it seems no matter how I adjust the map sensor, I get a horrible exhaust smell and even worse millage. I actually have good power now but If I adjust the fuel mixture until I get a good idle, the smell gets worse.
Of cores I don't have a co2 meter, so a rough setup procedure would get me going. Any tricks you might have learned or links you may know would help. I want so bad for this car to be practical to drive!

(And no I don't want to convert to megasquirt, sorry.)
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post #2 of 3 (permalink) Old 03-13-2009, 08:45 AM
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Easy method ($$), get on the chassis dyno and lean/richen till correct.

Traditional method (time and labor), check the spark plug color, adjust MAP sensor, drive 50-100 miles, do it again, I have done a few of these. Last time on a 1500 mile trip on a 450SL w/4.5...
Start rich, darken the plugs and lean to perfect performance. This must be done to correct for aging of motor. As the motor wears and compression declines you must lean mixture.

Question, how much oil used per tank?
Vacuum leaks, injector seals, intake manifold couplers, hoses?

The secret is to not move MAP sensor more than 1/8 turn per adjustment. (cclw) unscrew = lean, (clw) = rich. Add 1 Qt of cheap ATF per tank,

Brian O

Last edited by bostosh; 03-13-2009 at 08:56 AM. Reason: addition
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post #3 of 3 (permalink) Old 03-13-2009, 04:07 PM Thread Starter
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Originally Posted by bostosh View Post
Easy method ($$), get on the chassis dyno and lean/richen till correct.

Traditional method (time and labor), check the spark plug color, adjust MAP sensor, drive 50-100 miles, do it again, I have done a few of these. Last time on a 1500 mile trip on a 450SL w/4.5...
Start rich, darken the plugs and lean to perfect performance. This must be done to correct for aging of motor. As the motor wears and compression declines you must lean mixture.

Question, how much oil used per tank?
Vacuum leaks, injector seals, intake manifold couplers, hoses?

The secret is to not move MAP sensor more than 1/8 turn per adjustment. (cclw) unscrew = lean, (clw) = rich. Add 1 Qt of cheap ATF per tank,
It relay doesn't use oil. I don't need to add any between oil changes. I've checked for leaks many times and found nothing. It has 2 or 3 replacement injectors on it. I thought about replacing them all, but nothing leads me to believe their bad, plus it's $$.
I just can't seem to hit the sweet spot in the adjustment, to clean up the exhaust smell. And it always runs bad in the morning when it's cold. It starts right up though. And yes the IAC valve is good.
Thanx for the insight, I wish I had access to a dyno
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