When I start the jeep the engine shacks. changed the plugs and the fuel injector for cylinder # 4. started the jeep again the engine still shacks and it still reads misfire on cylinder #4. also replaced the thing the goes over the sparkplugs. Don't know what else to do.
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Re: 2002 jeep cheroke misfires on cylinder #4
Check intake gasket and vecuum hoses near intake runner #4. To do this spray carb cleaner at parting line between manifold and block while engine is running. If leaking rpm will dramatically change. A leak will lean out that cyl and cause misfire
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code p 0307 is misfiring on no 7 cylinder ====causes --- engine mechanical fault ---wiring---ignition/ fuel system--injector --ECT/MAF sensor---ECM
look for low fuel pressure or ignition control module
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
cylinder 4 misfire ,now if this is a GM product then i think you may need a reconditioned ECU init as if this is the 4 cyl engine and its same as the opel astra and zafiro and the vectra then its a common fault with a 2000 to 2004/5 model the computer is bolted to the engine inlet manifold and very weak and susceptable
Causes: - Improper spark plug at cylinder #1 - Insufficient compression at cylinder #1 - Incorrect fuel pressure - The injector circuit is open or shorted at cylinder #1 - Fuel injector #1 may be faulty - Intake air leak
When a misfire occurs, engine speed will fluctuate. If the engine speed
fluctuates enough to cause the Crankshaft Position (CKP) sensor signal
to vary, The Powertrain Control Module (PCM) or Electronic Control
Module (ECM) can determine that a misfire is occurring.
When is the code detected?
- Engine Cylinder #5 and #6 is Misfiring.
Symptoms: - Engine Light ON (or Service Engine Soon Warning Light) - Lack/loss of power - Hard start - Engine hesitation
Possible Causes: - Improper spark plug at cylinder #5 and #6 - Insufficient compression at cylinder #5 and #6 - Incorrect fuel pressure - The injector circuit is open or shorted at cylinder #5 and #6 - Fuel injector #5 and #6 may be faulty - Intake air leak at cyli
Possible Solution: - Perform Injector Service - Replaced Spark Plug #5 and #6 - Replaced Injector #5 and #6 - Replaced Ignition Coil #5 and #6
2. Vacuum leak
3. Injector fault
4. High or low fuel pressure. Thats the list of things to check. This is a #3 cylinder misfire. There is also TSB about #3 injector needing added heat protection. This could definitely be the cause. I start at plugs and go from there. Hope this helps. Thank you, Lee