FL Denmark

hello, i have a cherokee 4.0 L 6 il fron 1997, it has auto and 4wd. the other day i felt like checking my O2 sensor, because my km/ liter s... big time. it goes sonething like 5 km per liter.
the o2 sensor is working nicely, but i was supriced that the injectiontime in idle is 4.8 ms when the jeep is warm.
normally the cars i work with, have something like 2.6 to 2.9 ms in idle.
my question is, what is the ideal injection time for my 4.0 l jeep ?

thank you in advance, and sorry for my bad spelling and grama, im from denmark, so please bare with me.
btw. petrol in demark cost 2.5 usd for one liter. so thats why i want it to run as good as it can.

Hoooper

what do you normally work on? What Ive ever seen is that 2 ms is what an engine drops to on decel, thats a pretty low number. If youre used to working on small cars, with efficient engines, that would be the difference. Jeep 4.0L is not an efficient engine. Also, if the injectors are rated similarly for flow, obviously the 4.0L will need longer pulse times than a 2.0L

FL Denmark

i work on small european cars. thats proberly why i noticed it. but even a big engine can run with low pulse time, if the injector has higher flowrate. normally i would see a 4-5 ms pulsetime in the cold fase of the engine ( whit choke on ) if my jeep needs choke, would it then pulse with 8-9 ms that would be a very long tine

Bustedback

That is the normal injector pulse width for the 4.0 with OBDII.

Hoooper

your jeep is fuel injected with a choke? a choke serves 0 purpose in a fuel injected engine, that doesnt make much sense

FL Denmark

okay thank you

Bustedback

He means the injector on time is longer and acts like a choke to richen the mixture for cold starts.

FL Denmark

i know there is not a choke like on a carburator, but when then engine is cold, it normal that the pulsetime is longer to make the engine run richer, hense choke function.