Question about 1999 Jeep Cherokee
Hello Dennis. (no miles stated)
what engine, 4.0L I6 2.5L? I4
ever tuned it up? all spark and filters, the 60k mile, ever?
this post is random engine stalls?
so does it stall hot or cold or both
does it stall moving, right foot planted, cruisng
or only parked, or only as you come to a stop
do dash lamps/gauges or? go out before the stall? (look)
CEL off running.. ok, no DTCs stored if USA car. is it?
my guess is this stall can happen hot or cold engine.
location not in klondike (location not stated, so wild guess.)
hot stalls, ?
1 lets say coming to a stop. is very common EGR sticking open
2 never tuned up, ever or even the last decade?
3: ISC/iIAC sticking closed, jeeps love to do that any I4 , its a big issue. the idle stepper motor cone gets gummed up, clean it.
i clean both my jeeps, I4 ISC like 100 times since 1988.
4: bad TPS. but usually it throws DTC'S for this. if driven hard)
some I6' have no EGR valve. PCM has no EGR pins.!
you can monitor DC power at the CIG lighter, to see if power drops
at stall, easy, 13.3v to 15v is normal or ALT system is dead..
make sure the Automatic shut down relay is not being shut down
by PCM (DB/YL wire) goes to 12v is shut down, 0v is not.
the PCM can cut the ASDR for may reasons, oil pressure or battery overheat,? many, best it to find out of this RELAY is dropping EFI
off LINE. IT can .
lets do stalls.
i see tachometer drop below 800 RPM hot .
i try to save the stall, ISC stuck closed, and my right foot
opens throttle instictively and i save the stall.
easy, that is loss of air. see why?
on mine the stupid, ISC/.IAC works like this
the PCM remembers to ISC positions (stepper)
one cold start and one hot start (a secret i learned)
it then looks at water temps and guess (math) at a best start position.
if it used hot ISC for a COLD start the engine will want to flood due
to valve mostly closed, from last hot shut down,.
so floods, use right foot 10% ,
so i cant comment on what it might be until you state (displacement)
the engine temps. at fail
the operational mode, parked, stopping or between 5speed mt shifts.
if it fails parked in drive way.
or only moving or only coasting.
stalls on the fly?
im online at alldata.com and there are 16pages for PCM only.
this car the PCM controls the Alternator, (a software reg)
now another tack.
the car in usa, as OBD2, i connect my scan tool
and log, i drive and log. car stalls
i drive home ,play back my logs, and bingo
i see what happens at the stall, all sitting at my desk.
warm and dry.
lost comms,?. is DC power lost.
real live DTCS
some DTCS auto clear, at die.
some PCMs will reset the CKP or CMP sensor or spark failures.
so can only be seen live. (watching, 1 more secret)
now Bar stool answsers (any EFI car)
ever tune it up, ever do the 60K>? if not why not now?
lost spark, see if spark is being lost at stall, (at all plugs)
bad fueling, (too high or low fuel pressure at stall)
loss of air (ISC/IAC failed)
EGR (if there) stuck wide open,
if the engine runs perfect at most times, its probably ok
so is bad spark or fuel
spark is first. but not if never tuned up.
fueling is last to check , as PCM cuts fuel with spark failure sensed.
bad fueling can be bad injection or total loss of air supple , at idle.
Posted on Dec 15, 2013
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