Question about Jeep Cars & Trucks
Per previous sujestions, I have replaced the E3 spark plugs with the recomened originals..Have also replaced some sensors, like TPS, Oxygen sensors and others.. Had the PCM reprogramed as recomended a while back..
4.0L or 4.7L engine???????????????????????????
ILL NOT POST THE 50 causes, and guessing endlessly.
i guess getting car serviced is (off the table?) why?
the service manual does not teach diagnosis.!
only lame how to find open wires, endless...
its for service people that are ASE trained on this.
if you read books , real books , on this you will discover that there is a method for this. DIAGNOSIS
No engine stated, are we to guess engines here?
the sensor is for rich,
WJ jeep ,is the real name if in USA, are you?
yes many books show a list of parts that can be bad, causing a wrong reading from a new 02 sensor (100% ok)
what are they?
do you know what closed loop means (o2) and trim?
if not, it be real hard to learn diagnosis,
P0172 is a USA federal coded, invented by us, in 1996 by fed law.
it is universal in meaning, this one code P0 means fed codes.
P1 means factory only codes. p2, p3 same.
if you under stand closed loop servo systems, the FSM
seemingly confusing word become clear
the PCM goes rich, with O2 reading say 0v, lean.
that is how closed loop works on all EFI cars with 02
what that one fact you can see, that exhaust leaks,
they suck air between puTTS, and is 20 % oxygen same as you breath every day at sealevel
this 20 % oxygen hits the 02 tip and it SLAMS to 0v
0v is gross lean
the ECU then sees that goes rich and sets 172s.
there are other causes, "diagnosis"
what are they,
well do you have P03xx errors? misfire.
if one cylinder misfires each miss, sends what, a slug of oxygent to the 02,. and the 02 will see that, and the ECU goes richer.
the ECM can in fact make it worse.
so good spark is #1 here, as is full engine compression
not 50 psi,
1 leaking injector can cause gross misfire.
and air slugs. and 02 going nuts.
there are lots of tests. Ill not post all test, here.
but there many to find the cause,
but Id be all over exhaust leaks.
got 2 or 4 oxygen sensors
not telling me this makes answers wrong or obtuse.
are you using a real scan tool, $150 or a cheap useless $20 code reader?
the real scan tool does live data
what is long term fuel trim, if V6 both banks.
what is any other DTCs , pending
the 172 code has a Freeze frame this set of facts shows
other key readings during said failure, is see you didnt look here first. as you must.
and the live data on all sensors, at idle.
are the IN BAND (means reading correctly) (take a class on EFI?)(
if in band , I bet the 02 bank what ever, bank, front sensor reads
0v all day or reads wrong.
our scan tool I can plot o2 live data in a graph (voltage over time)
it must swing in the correct way. (im not teaching you that)
i have a real scope so i can see them all even on a 1993.
other than a simple exhaust leak
it can be misfire.
even in pendings. (push pendings on scan tool)
IF true there are 50 causes of misfire.
Ill list a few....
bad engine, say and intake valve on the bad bank
bad spark , or marginal, or gapped wrong.
injectors bad, sticking clogged or leaking. (simple tests with gauge)
vacuum bouncing, a simple test. and if true makes all EFI goes nuts...
fuel pressure wrong , out of spec. the FPR can fail here.
my guess you did not read chapter 25?
in the REAL BOOK
Posted on Dec 10, 2016
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Posted on Jan 02, 2017
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