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

Hello there D jet enhousiasts,

I have a early 914 107 in original condition.
At idling the mixture is to lean... aprox 0.12%
checked for air leaks, none found , although rubber parts have become hard...
drives good, Warm starts after a 5 minute stop are terrible...
how can i adjust the mixture on idling,
measurements on a four gas tester gives , no Co , only 150Hc , and about 12% CO2 with 2.3% O2 leftover...

best regards

Hi Unknown,

I would check injectors first and then switch to ECU / MPS combination that supports idle-run rheostat and thermo time switch.

Hi unknown,
did you check the fuel pressure?

Are all parts the original ones, especially the injectors?

Regards
Norbert

i realise i havent given many details, so here i go.
i have checked the throttle position sensor , it works fine. fuel pressure is a steady 2.1 bar... , axilary valve is in good working condition and closes completely after warmup.
i have co measurements with a cold engine from about 6.5%, but it does dissapear completely when the enige is warm. air temp sensor is aprox 285 ohms at 20 °C.
will check cilinder head temp sender today
will perform a smoke test to check again for air leaks .
the car has only 60.000 km from new, and everyhing is as original as can be, would you suggest i clean the injectors ultrasonic anyway as the Hydro carbons are only 150ppm? Injectors are yellow as they should be.
I have theasnu injectortester / cleaner and can perform cleaning and testing myself , but some injectors ( especialy worn ones ) do get stuck later on , when you are lucky they will get stuck in the closed position... but open can also happen, so i'm a bit in the twilight zone here regarding cleaning injectors with only 60k km....
thanks for thinking along
best regards Pascal.

about me? well i m a car enthousiast with a big interest in old cars, seven years ago i traded my job for the classic car passion and started my own shop. I have worked on D jet injected cars before, mostly Mercedes, and Volvo , have done another 914, but that one did have a mixture adjusting srew on the ecu... R107's is the car i see most of all. mostly k jet...

Hi Pascal,
I think it makes sense to clean the injectors. They get clogged not only by runtime, but by lifetime. too.
A car with such a low mileage must have been sitting for manyy years over all.
The alternative will be to make a spray - and flow-test only and not a cleaning.

You have to be careful with the injectors. Yellow ones could be those for L-Jetronic with much lower flow rate or chinese ones that wear the Bosch parts-# but not the Bosch logo.

All D-Jetronic-injectors have a parts-# below 0 280 150 050

Regards
Norbert

injector nrs are 0 280 150 009
ecu nr is 0 280 000 013 and Map 0 280 100 019 and following this website they match...
cleaning is in progress, i will test them tomorow if flow rate is ok , for now spray patern of 2 injectors is a bit off.
if injectors are ok, and co is still to low, what are my options then? since it is not adjustible at the ecu?
regards pascal

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