Tuning questions, car hesitates and part load stumble

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houseofdiesel

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Working on a 1975 3.0CSi. Engine was recently gone over and redone by specialist. Always had a tuning issue. Spark plugs no change and were reasonable shape. Electronic point conversion. New Bosch fuel pump 69414, fuel pressure shows 28-30 psi when driven. Timing is set to ball on flywheel with vacuum removed on distributor and 2500rpms. Car runs but stumbles and hesitates under part load. At full throttle no issues. Worst below 3000 rpm. Playing with the timing makes it go away. What am I missing or masking by playing with the timing? I have not found any diagnostic "trees" on the D jet for this car (values and specs).
 
houseofdiesel said:
Working on a 1975 3.0CSi. Engine was recently gone over and redone by specialist. Always had a tuning issue. Spark plugs no change and were reasonable shape. Electronic point conversion. New Bosch fuel pump 69414, fuel pressure shows 28-30 psi when driven. Timing is set to ball on flywheel with vacuum removed on distributor and 2500rpms. Car runs but stumbles and hesitates under part load. At full throttle no issues. Worst below 3000 rpm. Playing with the timing makes it go away. What am I missing or masking by playing with the timing? I have not found any diagnostic "trees" on the D jet for this car (values and specs).
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What to you mean by "engine was recently gone over and redone"? Did this include any non stock modifications?
Was the specialist a specialist with BMW M30 engines?
Which electronic ignition conversion did you use?
Can you define "playing with the timing"? Does more advance or more retard make it go away?
Has the car ever run correctly since you have owned it?
 
Clients car so going on second hand info. Engine was completely rebuilt. It looks factory fresh, block has paint and such. Not just a quick job. Injectors were tested, local known specialist went through it after client bought the car (he did not do the engine work). Idles high 1500 when cold. Takes 5-8 seconds of cranking to start cold. Never run right, no matter the fuel or temperature. Turning the distributor CCW makes it better (as facing on passenger side). Ignition looks like the WVE kit off Rockauto just a retrofit inside the distributor. The timing makes an immediate improvement but don't want detonation issues or worse down the road, this car is driven, rallied, enjoyed. I can invest time looking into various systems but lack the info on this engine/fuel system. It is very similar to VW's but not the same sensors. It never misfires, just stumbles. Removing injector harness on each cylinder makes a dead miss, not like that.
 
Is the vacuum advance working? With a dial back timing light, how many degrees of advance difference is there between when the vacuum advance is hooked up and with it disconnected and plugged at 2500?
 
There’s no vacuum advance on a csi.
its retard. Ported retard.
 
Make sure you are setting your timing light on the correct mark on the flywheel.

locate and set the TDC timing on the front dampener/lower timing cover

paint with a small brush the mark you see in the bellhousing opening on flywheel

in 4th gear slowly move the car until the second mark shows up in the opening. (7 teeth)

paint that mark a different color

now set your timing to the 2nd mark.
 
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Cap off the retard line at the manifold. Tune from there per Don, make sure you time to the "Z" ball not the "OT" ball. Or dial back to the "OT" ball.
 
That’s the correct port
 

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Then does the CSI use a different dizzy than the carbed CS, so that the advance curve is accomplished by mechanical/centrifugal advance weights and springs?
 
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