99 jeep grand cherokee 4.7L V8: pulled a few codes one that said random cylinder misfire and the other codes said misfire on cylinder 1,2,3. I checked for vacuum leaks but nothing recently had a tune up so spark plugs are good, throttle position sensor maybe six months old and i just changed the idle air control valve. when starting the engine idle jumps to about 1800rpm then goes down to 1000rpm then to about 500rpm then back to 1000rpm moves constantly between 500-1000rpm every 2-3 seconds.
Misfires are more from problem injectors, low fuel pressure or injector wiring than from plugs
have a fuel pressure test done to check for problem pressure regulator , problem fuel pump , blocked m/dirty filter
one other area of concern is the EVAP system where the purge valve doesn't vent the tank properly and causes low fuel flow rates
SOURCE: PO171 OBD-II Trouble Code " System Lean To Bank 1
Check PCV valve and be sure it is not stuck open. Check for vacuum leak at intake manifold.
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: 2001 Jeep Grand Cherokee code P1391
I would check to be sure that the timing chain hasn't jumped at all ..
SOURCE: 2004 jeep grand cherokee idling problem. Revs motor 200 to 500 rpms higher while driving.
I had the exact same problem on my 04 GC. I put some Techron Concentrate Plus Fuel System Cleaner in from Wal-Mart and it seemed to fix the problems right away. Let me know.
SOURCE: Where is the camshaft sensor located on my 99 Jeep Grand Cherokee
If you still have a cap rotor and ignition wires, it's inside the distributor. If not, it is the part where the distributor used to be (center rear of the engine behind the intake manifold)
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