What would cause my 92 4.9L to run very rich, idle bad, feels like its not getting fuel while driving. Has new fuel pump in front, removed rear. have checked plugs, vac lines, MAP, FPR, IAC valve, coolant temp, ambient air, TPS, pulled and cleaned throttle body, Scanner will not communicate

lots of causes , injector leaks sure. is one of many.
this is EFI and EFI only controls injection.(and spark)

it and all its inputs. do. called sensors.
1998 car in usa the scan tool tells you what all sensors are doing,called PID scans and DTC errors of any kind
25 year old car. and engine and all parts on it.

ALL fuses good?
NEXT:
scan the PCM see P03xx error or others? (scan it)
p0171 And P0174? P03xx codes and more do the scans.
engine good first. for sure this OLD.
we do engine tests.
compression over 150psi on all 8 cylinders.????
vacuum gauge at 20" HG at idle and not BOUNCING
we use tools to find cause. gue$$ing can be endless and super expensive or worse adding on wrong parts.
SPARK:
8 spark plugs all new, and all 8 COP boots new
boots never every lasted, 25years, nor spark plugs
and last fueling , cant burn fuel correctly with bad engine or bad spark CAN not.

SENSORs and stuff:
MAF SENSOR BAD OR WEAK, OR NEVER CLEAN IN 25 YEARS WILL RUN LEAN .
FPR 25 YEARS OLD ARE BAD. THEY ALLOW FUEL PRESSURE TO BE CRAZY TOO HIGH OR LOW
CALLED OUT OF SPEC. (or gets stuck at max PSI)
THE VACUUM HOSE TO FPR MISSING FUEL PRESSURE WILL BE WAY WAY TOO HIGH and super RICH BURN.!
IF FPR VAC NIPPILLE IS LEAKING FUEL IT IS BAD.
Fuel Pressure Engine Running kPa (psi) (28-45)
Key On Engine Off kPa (psi) 35-45)
THIS SPECS ARE DECEIVING,
EFI LAWS, KEY ON PRESSURE IS ALWAYS HIGHEST PSI. (DUE TO ZERO VACUUM)
AND RUNNING ENG AND VACUUM MAX INCHES HG, IS LOWEST PSI FUEL;. IF NOT RUNS RICH AS A PIG.
KEY ON PRESSURE FPR IS 5 TO 6 PSI FUEL LOWER THAN AT IDLE. <THAT IS ITS A#1 TOP JOB THIS.

EXAMPLE 40 PSI KEYON PRESSURE.
THE IDLE WILL BE ABOUT 35.(20 "HG IDLE)
THE FPR DOES ALL THAT.
IF NOT ALL INJECTOR , OVER OR UNDER INJECT.
PERSONALLY I NEVER EVER TRUST ANY OLD FPR. I HAVE HAND VACUUM PUMP TO TEST IT FULLY. AND HAVE FOR 4DECADES.MID 1980S

INJECTOR LEAK DOWN TESTS FAIL OR INJECTOR BALANCE TEST FAILS ,TOLD IN SM= SERVICE MANUAL.
BASICS BAD: IS THIS:
THERMOSTAT BAD. OR MISSING, OR NOT AT 180F TO 200F TEMP STUCK AT 150F BAD BAD BAD.

ECT BAD, SHOWS 150F WHEN COOLANT IS 180F
CAUSING:SUPER RICH INJECTIONS.
SO PCM IS STUCK IN COLD STARTUP MODE FOR EVER AND BURNS FUEL LIKE MAD.

SURE O2 SENSORS DEAD OR EXH CRACKS NEAR BY THEM MAKES THEM LIE AND EFI GOES HOG WILD RICK. SURE.

WHY NOT SCAN THE PCM FIRST.
AND SEE WHAT IS WRONG FIRST.
SAVE TONS OF GUESSING

LAST AND NOT THE LEAST
YOU CAN SCAN ANY PCM AND SEE IF IT IS IN LIMPHOME MODE AND IF IS, IT BURNS FUEL LIKE CRAZY
AND SEE TOO ,CLOSE LOOP MODE IS DEAD
FULLY HOT ENGINE.
YOU CAN SEE LTFT EFI IS STUCK FULL RICH.
AND DTC ERRORS ,LOTS?
THIS IS NOT GUESS IT IS TESTING USES REAL TOOLS. TO FIND CAUSE.

secured.means what? in what country?
what engine.
parked key in pocket?
is this the CNG engine (compr,natural gas) or gasoline (petrol)
tell what fuel this car uses first, I will answer for gasoline
1.7L gas or CNG?

first is to not guess, 100's of related parts;.
get the car serviced as 99% do.?
not told at all if car smells gas

• parked, (short or long time)
• moving
• or at idle packed,
• or windows down driving or what? or even windows up, blower off.

MPG shot. that is running smell, and wasted fuel max.

so means engine is running super rich and not the pump is not bad.
FPR many be.bad. up FRONT LNG, but in fuel tank GAS.(petrol)
Is the check engine lamp (cluster) glowing driving ,I bet it is and is ignored by you,? FPR are high fail rate this old. sorry

scan the PCM is next. scan it see lots of errors you will called DTC
all scan tools work on your USA Civic.
but no country you told and matters HUGE ON SCANS !!!
now Gasoline engines that fail rich and stink, rich.

1. fuel pressure too high, FPR bad.
2. leaking injectors, or stuck open or closed.
3. gross misfire spark, bad, spark plugs 21 years old have zero chances, or bad COP boots or bad coil pack HV wire sets or all.
4. bad engine or has lots of causes. or cam belt slipped no engine told. cam belt never lasted 21 years ever then slips. and goes super rich fuel and very low engine power. 60-100k miles life span or 5 years. max. did you ignore belt service?

FPR means Fuel pressure regulator, gas engine is in the tank.
a pump puts out near 60PSI but the FPR knocks this pressure down
and also keeps it steady. atr.

scan the PCM if CMP/CKP errors both the cam belt slipped.
P03xx errors. scan it now.

no. (but the isc valves loves to stick but will not cause black smoke)
the 4.0L is one of 5 million made, it's well known,
the black smoke don't lie. it's rich and the cat seems burned up too.
as with black smoke the cat will try to catalyze all that and glow red hot. is your cat missing?>
so why not believe the code 171, its real and is catastrophic failure. there are 2 engines here, FED and California.(exhaust)
(2 different exhausts and sensors there.
as they say, fix what is OBVIOUSLY bad, 171
(find why using tools or inspections)
Fuel System Lean (Bank 1)in most cases the exhaust is cracked near B1S1 0xy sensor
this causes it to stick at 0volts, (lies) and the PCM sees that obvious lie then goes rich. (limphome rich)
if the pcm cant measure oxygen, it must now guess at fuel trim.(bad that.)
it goes rich, so you dont melt pistons running lean.
(by design)

bad front oxygen sensor (aka , up stream bank 1)
in calif cars, it can have a split exhaust on the I6 and have 3 sensors. (hope not yours, do look..)
most have 2 sensor, front and the useless behind cat sensor(B1s2)
S2 is useless for running mix, the rear is for smog test the cat.

so it rich, and now misfires. and the spark tips are black.
and it misfires to bad it can even idle, sure. (Drops)
the cause, is too rich.
the 171 means the PCM sees it stuck at 0v forEVER.

there are in fact other causes.
but these 2 are top cause.

on all 3 of my 4.0L engines
the exhaust manifold cracked on the under side.
side facing block. (i use a hose to ear to hear the putt putt puts, (with FULL PPE protection from burns from a dead cold engine.) ask how.
even the SST exh. man. did that.

or the header flange gasket is TOAST. (that too putts when bad.)

how many miles on the odometer, mines 95k.
ah a v6, P0306 is #6 misfiring. 2.5L V6
300 is all 6 misfiring.... oops.
it is. for sure.
misfire is cause by many things, only 3 in physics, but many real world. (compression + spark +fuel rates)
i works this easy, way.
i have a full scan tool not just a code reader (near useless it)
i make sure my V6 (I have an 04) holds closed loop at idle and 2500 rpm. i f not , fix that first.
easy, it is. just look, bingo, Open loop, (out of control)
fueling is out of control.
but, first i do that tune up. in the manual, 60k , 120k, 180k, see?
do that first. , spark plugs dont last foreever nor filters.
then i replace both front 02 sensors at 100k miles. there design life.
V6 has 2 front sensors. (rear can , just sit and be ignored)
if it misfires. now, i toss a coin.
compression or fuel pressure.
i can do both in 30min flat but i toss coin lands on fuel.
i check fuel pressure and its.
60psi, fuel regulator is bad,
20psi, same, or bad pump or bad 12vdc to pump, 8v to pump is bad wiring.
one thing that helps is to find out if the engine is running too rich or too lean.
and if there are cracks in the exhuast near the 02 sensors.
i force the EFI rich and lean watching both 02 sensors in my scan tool
to see if i can force them lean or rich.
on the v6, we can introduce air leaks, to the plenum.
this will cause lean, and the o2 most react to my lean forcing
or its dead.
i can force richer, if i suspect lean or 02 shows lean, by
removing the Fuel pump regulator hose (vac) and plugging hose fast.
this causes the FPreg to go to high pressure. max.
causing RICH>
i watch the 02 and see it go rich, if not the 02 is bad or you have exhaust leaks, or dead cylinder causing the 02 to fib.
you have 2 banks, and both banks are running off 1 MAF
so you can look at both 02 sensors (front) B1S1 and B1S2
and see if both react the same. to my forcing's.

i dont think you have 3 bad cops out 6. no.
if any cylinder misfires on bank one, then bank 1 o2 goes nuts
same with the Bank 2. this can aid troubleshooting having 2 banks.
the MAF can not lie for 1 cyclinder nor one bank
the 02s can lie for each bank,
both are key to diagnosis.
let me give an example say
injector 1 leaks.
causing 301s
v6
246
135 left
this is your lay out.
my guess is its not lost compression (no test guess, mostly useless)
not 2 bad cops one on each side will cause 300s
not one bad cop. as other side would be ok.
not one bad injector.
my guess, is fuel pressure is way off.
but///???
or maf running lean (dirty, spary clean it 12inches away not close)
low fuel pressure
too high fuel pressure.

all comments are for engine with 60k mile service done,
60k, 12ok, etc.

so you ignore the hard DTC fails.
that is odd. why do that?
you do know a stuck open EGR cause most stalls and tip in
bogs, right?
a bad 02 if the front 02 , can cause too rich or too lean running
too rich fouls sparks, and too lean causes bogs.
but not accelerating as the 02 is dead then.
bad TPS can cause tip in bogs, in fact that is its #1 job.
called ENrich mode during acceleration.

not checking fuel pressure is bad service.,
the car must have 30 psi pressure at all times.
not 5 not 10 , or 20 or 60
30 (the FSM has the spec, for each engine , not stated)
if the fuel pressure is good, then forget the pump or regulator.
good means , at spec . not useless squirt tests....

the 4x4 cars have insensitive P0300 misfire detection due
to preventing offroad false misfires reported.
so most 4x4 drivers feel it first way, before P03xx happens.
this is normal, but not misfire.
why not post the real o2 code. there are many.
post them all. the real codes.
post here.
http://www.fixkick.com/bbs2/Suzuki-bbs/forumdisplay.php?fid=2

rich,101
this is a MAP , speed density EFI fueling system,,,,
not misfiring.
in no order,

1. map reads, low all the time cause rich, (low means low vacuum that is real) the ECU sees that and adds huge fueling.
2. fuel pressure way too high bad PFR.
3. injector leaking i do an injector leakdown test, or balance test, like the book shows. (and has 3 causes)
4. front 02 sensors struck lean , forced ECU to go RICH. Any exhaust (its air sucking in) leaks, cause the 02 to go nuts or stick at 0v all the time. and RICH will happen. unplug it , get better?

we use simple tools to find this.
is vacuum at 19 inches HG at idle.? hot? sealevel #s/
???? clean the map yet?

Stalling and running rich. I have seen this before on a Camero. The fuel pump was weak. Not making enough pressure. This caused the fuel injector to DRIP gas instead of SPRAY gas. This caused the fuel to flow into the cylinder in a liquid form, and it did not burn well. We put in a new fuel pump and the car came to life. Good luck.

Fuel pumps just supply fuel to the carb. Either they work or don't work. I would make sure that the mixture screws on the carb are set properly. Turn the screws in to lean out the mixture, do one at a time.
You want to turn the screws in to the point where the jeep will start to idle rough and then back out a 1/2 turn. Check your timing also. If the jeep has alot of miles on it, the timing chain will stretch and it's possible that you cannot get the correct timing.

it can cause it to run rich because the oxygen sensor may be getting a false reading as to how much oxygen is there....this in turn causes the pcm to add more fuel

i think it Needs a tune up.

A bad Fuel Pump can cause starting problems and so can a bad timing belt. How many miles are on the car? If it's more than 100,000...take a look at your timing belt. Is it worn? Chrysler recommends replacement at 60,000 but some last up to 100,000. Any longer than that is pushing it and asking for a problem. A bad fuel pump will not allow enough fuel to fire the engine.