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Discussion Starter · #1 ·
Hello,
My "new 300td" doesn't seem to have the power the other one has with 3 times the mileage. I am wondering how to adjust the fuel and turbo boost to maximize power and fuel mileage. I recently did a valve adjustment and this made a huge difference but it still lags behing the other car.
Please help, Brent
 

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C215-CL500 & W140-300SE
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1/4 clockwise turn of the ALDA should do the trick.
 

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77 450 SL
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Go ccw btw, not cw. I just did mine, 1.5 turns, and it's a new car.
 

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82 300D VNT, 80 240D 3.0T
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DO NOT adjust the ALDA.
Doing so only masks the actual problem(s).

Its adjustment should be the absolute last thing to do after every other possible problem area has been addressed.
 

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So after doing valve adjustment, changing both fuel filters, cleaning banjo bolt/hose, checking compression, timing chain stretch, IP timing, what's next? Bestow unto us your wisdom. OP, make sure you check all of these as well.
 
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82 300D VNT, 80 240D 3.0T
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Okay smartass, you forgot (in no particular order) EGR operation (removal), throttle linkage travel, throttle linkage adjustment, fuel pressure (lift pump, check valves and relief valve), injector spray quality (and pop pressure), CCV restriction, manifold leaks (including turbo to intake o-ring seals), fuel tank vent, fuel tank strainer, fan clutch operation, engine temperature (and replacing the sensor if over 10 years old), oil cooler thermostat operation (if oil cooler gets hot), front end alignment, brake drag, vacuum system operation, transmission adjustment, all 3 drivetrain mounts, exhaust system restriction (collapsed muffler/resonator), alternator charging voltage, A/C compressor and clutch operation, tire pressure, differential free play (pinion slack) and THEN adjust the ALDA because you've covered everything thats more likely to cause performance issues.

Did I forget anything?

EDIT: Damn, forgot "check the ball joints".
EDIT 2: jeanmarc109 added the overboost solenoid on the firewall.
 

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Discussion Starter · #7 ·
I have replaced the fuel filters, the injectors, and primer pump. The car has excellent compression.
Thanks, Brent
 

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Go ccw btw, not cw. I just did mine, 1.5 turns, and it's a new car.
I stand corrected on the direction(typo), but still believe only 1/4 ccw turn is necessary.

Or try an Italian tune-up...get on the highway, mash the throttle and blow all the crap out the exhaust.
 

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money pits of various forms
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Check you linkages first as Zedd says. This is most likely to be the culprit. Once you have adjusted the ALDA from factory spec there is no going back. In many states this is illegal. Your EGR could be plugged, your alda lines are probably plugged and fuel pressure is probably low. Adjusting the ALDA is a quick fix to mask real issues.
 
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Discussion Starter · #10 ·
ALDA tuneup

What is involved in doing an alda tuneup? Since it sounds like a bad idea to adjust it. The fuel tank vent is working fine.
Thanks for the help, Brent
 

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Check out the DIY on dieselgiant.com.

Its pretty std. Is the turbo kicking in at all?
 

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1983 300D Turbo
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I had the same problem & found the gyzmo between the banjo bolt and the Alda was the culprit (sorry I forget the technical name for it) it's on the firewall near the the brake booster. bypass it to see if performance improves. if so it's a cheap and easy fix.
 

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The turbo kicks in not as quick as I would like though. Is there any way to adjust this?
More than likely your ALDA lines or banjo bolt are plugged. ALDA is a fuel cut off device which increases fuel with boost. The other option is that you wastegate spring has weakened (common) and your not providing enough boost. Start with cleaning the ALDA and report back. Takes all of 20min tops.
 
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2013 MINI Copper S Clubman, '84 300CD-weekend car
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I had the same problem & found the gyzmo between the banjo bolt and the Alda was the culprit (sorry I forget the technical name for it) it's on the firewall near the the brake booster. bypass it to see if performance improves. if so it's a cheap and easy fix.
I believe you're referring to the switchover valve. A protection (redundant IMO) device. It may have failed or gotten clogged up. If so it may send a signal to the ALDA to limit fuel.
 

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I believe you're referring to the switchover valve. A protection (redundant IMO) device. It may have failed or gotten clogged up. If so it may send a signal to the ALDA to limit fuel.
Not to nit pick but its kind of the opposite. The switchover valve vents to atmosphere when boost > 16psi. It can also get plugged. Its lack of a signal that limits the fuel.
 
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^ Okay, thanks for the info.
 

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Discussion Starter · #20 ·
Thanks

Thanks for all the replies!:) The banjo bolt on the manifold was clogged as you guys said. It runs like a scalded dog now. I am worried though, the alda adjustment has been tampered with. Is it possible to run the car too lean? It never smokes at all. The engine has 182,000 miles on it. Even going up steep hills with it floored I never see smoke.
Brent
 
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