D Jetronic low to mid throttle surge

Hi Tim,

if you are sure about false air and MAP sensor then verify:+

• cold start valve not injecting
• both temperature sensors on ECU connector

Hi Volker, I've swapped in a spare cold start injector, will check tomorrow morning if it makes any difference. Can they fail and continuously inject fuel? This would lead to a rich situation which can't be tuned out. Are they serviceable? I've seen some for sale but at £200!
Thanks Tim

Hi Tim,

yes they can leak and can be cleaned by ASNU serive. Also their electrical control via thermo time switch and sometimes relay could be broken.

Hi, does the air bleed screw that's adjusted at idle make any difference to the mixture when not at idle?
I've been playing with the wideband and fuel pressure while driving and have found that the car runs best with the pressure under 1.6bar. This is assuming the gauge is correct. Over this it is too rich and hesitates at partial load. At 1.5bar the A/F rarely gets above 13.5 so is still safely rich.
There maybe something else wrong somewhere. I don't have to worry about emissions testing here in Australia.

Hi Tim,
following the calculators reducing the pressure to 1.6 Bar means the engine gets about 10% less fuel.
'Only' 10%, not 20% as one could think.

Did you already check the resistances of the temp sensors?

Check them at the ECU-connector (not directly at the sensors) using an Ohmmeter, here is a link for downloading

regards
Norbert

edit: I never had the chance to verify this plan up to this moment. Try to read the air temp sensor against pin 11, too in the case pin 13 shows endless resistance.

Hi,

the idle.run air-bleed screw is like a foot on pedal. it does not affect mixture. Fuel dimensioning is done by D-Jetronic.

A pin-out of whole connecotr is in appendix B . 10-20% too much would fit a missing air temp sensor.