MFI engine hesitation when speed switch/RPM transducer connected

[frederik]

Sounds like your transducer is affecting the distributor signal. Try swapping it with a known good one. You can disconnect it, but this could lead to excess fuel diluting your oil, accelerating engine wear.

[RSTarga]

Sounds like your transducer is affecting the distributor signal. Try swapping it with a known good one. You can disconnect it, but this could lead to excess fuel diluting your oil, accelerating engine wear.

This is not true, I have run with and without, never able to discern a difference. Main cause of backfiring is not taking your foot of the pedal completely on decel.
I think that was the original motivation as fuel mileage difference is not apparent.
But others may have a different opinion or results.

[SFE]

Sounds like your transducer is affecting the distributor signal. Try swapping it with a known good one. You can disconnect it, but this could lead to excess fuel diluting your oil, accelerating engine wear.

Today Porsche delivers only one reference for the transducer and back in the original days there was several references for that relay.
So I think it’s a good idea to try another transducer on my car.

[frederik]

This is not true, I have run with and without, never able to discern a difference. Main cause of backfiring is not taking your foot of the pedal completely on decel.
I think that was the original motivation as fuel mileage difference is not apparent.
But others may have a different opinion or results.

Well my Targa backfired a lot less with the transducer working correctly. You do get excess fuel otherwise, some of that will be leaking down into the crankcase. How much is difficult to tell. I just know I enjoyed it when I managed to get everything working as intended.

[SFE]

Well my Targa backfired a lot less with the transducer working correctly. You do get excess fuel otherwise, some of that will be leaking down into the crankcase. How much is difficult to tell. I just know I enjoyed it when I managed to get everything working as intended.

Well the goal is definitely to have a transducer working on my car.
Next step for me is to rebuild my original relay et check if it is working better than the brand new Porsche I bought.

[SFE]

Still trying to understand why when I connect the transducer my idle is perturbed....on my 69E.

My tach is newer compared to my car that's for sure because it is connected directly to the distributor (black/violet wire) and it has a TD pin in the back...but it is working very well.

When I check the wiring I found 2 non connected wires, probably those wires were dedicated for the "intermediate unit" which is not installed in my car anymore.



What could be wrong with my wiring which is adapted to my newer tachometer ?
I'm pretty sure someone has a newer tach AND a transducer working well in his car !!!

[tom1394racing]

Here is a wiring diagram showing the layout of the engine relay board. You can see the brown (ground ) wire and the red/white wire are the connections for the ballast resistor (intermediate unit). The third connection to the ballast resistor is the connection to the tach which you have correctly bypassed.

You can also see the connections to the RPM transducer (RPM sensor) including the connection to the stop solenoid (stop magnet).

You can check the RPM transducer by following these instructions:

[SFE]

Thanks Tom, interesting to read that they recommend part number 90161511300 !




And as you can see Porsche sells only this part number :

[SFE]

I've compared my wiring to the original diagram sent by Tom :

Original :


My wiring :


Main differences :
No ballast unit.
There is a black/violet wire connected on the distributor and going probably to the tachometer.
No black wire connected between the coil and the distributor.

[edmayo]

You have no high tension lead to the distributor???