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ALDA Baseline

1350 Views 7 Replies 4 Participants Last post by  DarkLurker
The ADLA (ALDA?) on my 1980 300D was "tuned" by some sort of expert(?) before I inherited vehicle and I think the "tuning" may be causing sysmptoms below...

When accelerating from a stop, if the reves are kept very low, the 300D emits almost no smoke. If accelerating normally, not racing away, 300D emits clouds of dark gray smoke like a smoke screen. 300D runs well at highways speeds and smoothly around town and produces no smoke above 60 MPH. I assume the smoke screen is caused by unburned fuel resulting from too rich a fuel mixture - a fuel mixture richness caused by the ALDA?

I change oil and oil and air filters at prescribed intervals. My question is - How do I establish a baseline for the ADLA so I may try to reduce smoke screen? Seems like turning the screw without knowing where zero is would cause more problems.
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Before adjusting the ALDA make sure that all the pressure lines are clear. The most common culprit of problems is the banjo fitting on the rear of the exaust manifold. If it gets clogged, the alda will recieve a false reading and will restrict fuel as not to create an overboost situation. These old cars make smoke for a variety of reasons. On my 84 300td I spent way too much time messing around with the ALDA. I had the same symptons that you described. The adjustment will only work as a fine tuning and likley will not fix your smoking problem alone. I would change filters, do a valve adjustment and pull the injectors and clean them along with all fuel lines. The one single thing that made the biggest difference was to take the car our on a long hard run and blow out all the crud that collects in the intake manifold. I drove mine about 200 miles. When I pulled out of my driveway (Running the rpms high) I put out a cloud of smoke that stopped traffic. By the end of the roadtrip the car did no smoke at all. Short trips and not letting thse engine warm up allows the intake to get clogged. Hope this helps.
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