it won't be vacuum leaks! (assumes FPR is working, if vacuum path fails to FPR or MAP all bests off)
this jeep engine EFI is called the
Speed Density system , so that all vacuum leaks cause racing fast RPM at idle and full % HP power and not rich ever.!
vacuum leaks on this engine work just like you stepping on the throttle pedal which is only and air pedal (vacuum leak by you)
this is not a MAF engine say some Toyota, called
air density system. at all.
forgot maf inducted engines.
WE test the map and FPR both, first. if engine is assumed good and is a huge age related, thing to assume.
if the map fails to get vacuum to it the ECM can not compute fuel rates now.
The map sensor high (high vac HG inches) causes low injections rates and if VAC is stuck low ( at low Hg inches ) the injection rates are lower.
and all Hg reading between.
The FPR must also not be dead, stuck high or fails to regulate at all speeds and engine loads. all.
here are the mAP readings
i made nice exel graph. as vacuum drops as you near WOT The hg goes low and voltage rises to 4v or more. I made this off my JK.
vacuum is about 20 at idle and for SURE
NOT BOUNCING, oops a vacuum gauge finds that.
chapter 14, your 89, map page 48 states
The voltage
should drop to 1.5 - 2.1 volts with a hot, neutral
idle
speed condition.
Test ECU terminal 33 for the same voltage described
above to verify the wire harness condition. Repair as
necessary.
Test the MAP sensor supply voltage at the sensor
connector terminal C with the ignition ON.
The voltage (
keyon engine off)
should be 5 volts (±0.5V). Five volts (±0.5V) should also
be at terminal 16 of the ECU wire harness connector.
Repair or replace the wire harness as necessary.
,
and now a simple free test,
unplug the 02 sensor and drive. no more smoke black?
this year car the 02 is too powerful, cured by USA laws 1996,
that means if 02 fails and sticks at 0vdc, it goes way way too rich.
so unplug it.
also exhaust leaks any where near the 02 bung, will cause huge rich conditions. (air is 20 times more oxygen than any o2 sensor can stand)
at its tip running. cracks happen.
last the parting shot.
engine good, spark good, then last is all fueling tests.
ASE.