It means only, that combustion energy on cylinder 3 is weak.
it can be :
bad spark. #3
bad fuel ratio (lean or too rich) #3 (injectors)
bad compression. #3
we find it by doing tests, with simple tools
do you want guess or test?
SOURCE: Jeep Hesitates. P0303 code
Check the cylinders Commpression. over 115 psi is good, 120 psi is normal.
SOURCE: 2002 Jeep Grand Cherokee Lardo misfiring
You say you changed the cam sensor. A1391 code is a crank sensor on the top of the trans. bell housing.
SOURCE: firing order for 1997 jeep cherokee straight 6 cyl.
153624 On cap #1 is two towers clockwise from right side hold-down screw, #1 is front cyl on engine. Firing order is clockwise.
SOURCE: MISFIRE CYLINDER #3 CHECK ENGINE LIGHT COMES ON VEHICLE
Check spark plug wires for corrosion
SOURCE: P0308 cylinder 8 misfire detected? How to repair?
Fuel injector cleaner commonly has a low success
rate, and will not help if it's more than one cylinder that is
missfiring. The fact that you have a "rattle" noise, leads me to beleive
the engine is not receiving fuel on one or more cylidners. If it is all
the cylinders, than the fuel pump may be the culprit, or the fuel pump
circuit. But if only one cylidner is missfiring than it is a possibly an
injector. A code P0300 refers to all cylinder missfires, and any code
between P0301-P0308 distinugiushes a particular cylinder.
Misfiring
1- a general electrical tune-up (spark plugs, wire set, cap &
rotor) is a basic start to cure this issue. Wiggle the dist shaft while
you are in there, if you have one.
2- Then a good carbon cleaning / throttle-body cleaning.
3- Vacuum leaks at any of the hoses that connect to the Intake
manifold; especially the MAP sensor connection.
4- If that does not help then the O2 sensor could be bad or drifting.
5- Funky coil/coil-packs
6- Theoretically a microsecond glitch in either the cam or crank
shaft sensors would cause this, but I am not aware of this as a typical
cause.
7- Lastly a funky PCM but again it is not common for this to cause
miss-firing.
Note for the V8 then also:
a) bad erg valve (this dilutes the combustion gases and hence raises
the combustion temp
b) a leaky plenum/Intake manifold gasket. Leaking Intake gasket
symptoms
Also can check the TSB 18-48-98 Ignition System Cross Fire/Secondary Ignition Wire Induction (Complete Version )
Hope help with this (remember rated this). Good luck and have a nice day.
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