yes it can be adjusted, the FSM is free
I will paste that here to you in the carb fuel chapters,
90 yJ 4.2L
BBD carb.
just saying.... if you have a 34 old jeep, get the FSM first. and learn to fix it your self
most shops the techs there never seen or touched a car this old. for sure MCU BBD carb wonder device there.
the choke unloader mech. releases the choke (from hot mode) to cold. and also raises the thorttle plate for fast idle. cold start
the fast idle is also called a fast idle cam. and it too has spec. adjustment.
chapter 14, page 122 is where it starts for 4.2l liter engines, the book cover all fueling of all enfine that year. YJ and more
the main jets are stepper motor , MCU ( computer controlled and uses 1 OX sensor to do that in closed loop mode.
The chock is old skool (sic)
and 1, KS knock sensor tool and lots of thermal switches , WOT and more.
step1 , make sure the altitude jumper is not in place (jump it over 4000ft, altitude) what the PO did here is any wonder, so look.
step2. the SOL vac , must work and idles switch and relay so the idle controller can work hot and cold both. page 126
the system is very complex , compare to a simple real carb. yours is e_carb. (horror)
step 3 is the choke relay told page 128 and needs a working oil pressure switch to do that , as it states. see the 2 fuses p130?
the pages go to p156, with complex carb related diagnostics.
this ends CEC end of this carb
page 104 is BBD basics, to p121 Chapter 14, only
page 105 cover the chock adjustment/
the choke is electrically heated, if this burns out (gee 30 years old) the choke is dead.
read page 107, it tells you the carb must be removed to fix or set the choke up. (but the oil pressure switch must work)
the choke is color coded, it says and we set that based on 3 factors climate , altitude and if a relic choke there we may need to go richer for it to work, if it works at all , sure.)
page 118 unloader adj.
and last 119, choke actuall colored settings for gold ,red, or green model index.
the fast idle cam must be set too, per the book. in order .
free to read here (huge chapter 14 and 104 on)
PDF ICON first one, is BINGO
I thought that this might be helpful to fellow YJ owners to make one sticky resource thread with all of the original factory service manuals and parts catalogs for 1987-1995 Jeep Wrangler YJs. If you have anything I'm missing, please feel free to post them in this thread and I'll add them to...
wrangleryjforum.com