Nissan Repair: rd28 Cold start idle issues, fuel pressure regulator, c33

Question
QUESTION: Hi there,

I am having trouble with my rd28 which I am assuming is automatic choke.. on a cold startup it will idle fairly well for a while but when left for 2-3 mins it will suddenly drop about 500rpm and will only idle for a few seconds at this level before stalling. Also putting it in gear (auto) can stall it, but that is less of a surprise with and old, cold diesel.
When warm it actually idles higher than when it is cold, which is why I am assuming choke issues..

Any help would be greatly appreciated!!!

Another point of note, it sounds like it is a controlled thing, each change in revs is fairly sudden, it's not like it gradually gets up in revs as it warms up..

Cheers,
Ben

ANSWER: Ben,

Send me the year of the vehicle.  It sounds like the fuel pressure regulator is sticking for one.  Second, the choke is probably sticking.  Pull the thermal cover off the choke and check for proper operation as it appears the choke is sticking once it drops to idle.

---------- FOLLOW-UP ----------

QUESTION: Year is 1989.  Laurel Medalist c33 with rd28.  I will check out the choke in the morning when I start it cold.
Thanks!!!!!!!

Answer
Ben,

Thanks for the year and model.  I say the choke and fuel pressure regulator since it idles higher when warm.  I would assume the filter has been changed?  If the filter is clogged, slightly, it can cause fuel pressure issues as does the regulator.  I say this since it sounds like it is running a little over-rich at cold start and after it transitions to warm, the jump in idle, then it idles too fast, after warm.  Check and clean choke and check the fuel pressure too and see if it is off a bit.