914 1.7 d jet , early type without idle mixture adjuster on ecu.

Hi Pascal,

to be honest, there is no other option than swapping ECU / MPS to a version with rheostat.

auwch... that was not the answer i needed to hear...
will measure again after i have mounted the cleaned injectors on the car, but i am afraid the result will remain the same... have claened them twice , and flowrate is the same, so there will not be any progress

regards Pascal

Pascal,
even if you don't want to hear this, but the older ones aren't adjustable. Thats a fact. Remember these have been the first ones on the market.
I have had a similar problem, but too much CO. I changed everything to the latest available version. But cylinder and pistons were worn out, so I build an engine with new ones. Now, I can adjust CO in the range from 0.3 .. 2% with the potentiometer.

Marc

Hello  D jet entousiasts,

an update on the 914  1.7 porsche
I have cleaned all injectors several times , flow rate is a bit higher, before cleaning i had 70cc per injector.
after cleaning a had a bit more 74cc  both on a 30 sec simulation at 1666 tr/min but with larger opening pulse..
naturaly equipped with new injector filters, pintle caps rubber mounting rings and a brand new ethanol resistant fuel pipe..
The final results are reasonable, for my sake still a bit low on Co an a bit high on HC, but certenly driveable and now there is time to search for another ecu and a map sensor
exhaust values 1.17    % Co , produces 12.25 Co2 , O2 leftover is 1.29 and Hc is 312ppm @idle of 820 tr/min.
 
 best regards

Pascal

Hi Pascal,
hardly believable so little difference in flow makes such a difference in CO value.
I think the new seals will have had some influence, too.
The injector's flow rate has to be 265 ccm/min at full, continuos opening at a maximum of 5% in tolerance.
It would have been interesting to know the values of your injectors...

I know 914ers in the U.S.A like to manipulate the MPS. Maybe this has been done to yours, too? It has some influence at idle, too.
And this could mean the car runs lean in other conditions, too.
Did you check the sensor, does it show signs of manipulation? jetronic.org/en/d-jetronic/mps

The 'missing' rheostat at the ECU would have influence only at idle, as you know. A mistuned MPS would effect the engine combustion under all conditions.

One last question: Did you adjust the valve clearance? This would effect the combustion, too as I could learn in the past.

Regards
Norbert