If CMP sensor is not operating properly, ensure CMP sensor is installed correctly, and timing belt and gears are not damaged before replacing CMP sensor and go to step 21.Ħ. If CMP sensor is operating properly, go to next step. Diagnose and repair as necessary and go to step 21.ĥ. If any PID data is not within specification, go to applicable test. If all PID data is within specification, go to next step. Record PID data for ECT, IAT, MAF, RPM, TP and VS. Referring to FREEZE FRAME DATA, operate vehicle under same conditions as when DTC was set. If any PID data is not within specification, go to applicable test iand go to step 21.Ĥ. Ensure all signal data is within specification. Using scan tool, access ECT, IAT, MAF, RPM, TP and VS PIDs. If DTCs are present, go to appropriate test.ģ. If no other DTCs are present, go to next step. Turn ignition switch off and then start engine. If repair information is available, perform diagnosis and repair as necessary. If repair information is not available, go to next step. Check service bulletins for repair information related to this DTC. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Vacuum hoses damaged or improperly connected.ġ. Possible causes are:Ĭamshaft Position (CMP) sensor malfunction.Ĭrankshaft Postion (CKP) sensor malfunction.Įxcessive air leak in intake-air system between Mass Airflow (MAF) sensor and dynamic chamber. MIL is illuminated when PCM detects malfunction during 2 consecutive drive cycles. If misfire ratio exceeds a preprogrammed criteria, PCM determines that a misfire has occurred which can damage the catalytic converter and will set a DTC. While engine is operating, PCM counts number of misfires that occur during 200 crankshaft revolutions and during 1000 crankshaft revolutions in order to calculate a misfire ratio for each crankshaft revolution. PCM detects a misfire in a specific cylinder by calculating change of CKP interval time for each cylinder. PCM monitors Crankshaft Position (CKP) sensor input signal interval time. Since problem started after timing belt replacement, I woud suggest checking the CMP first. Random misfire is always a troublesome problem to resolve as there are many possibilities. I'm completely lost at this point, what should I look at to cure this problem? EGR valve, Ignition coils, etc? Which tells me the cat converter has gone south due to unburnt gasoline from the mis-fire getting into it. After driving it like this for a few weeks a new code has come up for "bad warm-up catalist". They said bring it back when it dies or is just about to, it would be easier to find the problem then. They even had the car for two weeks but just gave up on it with no charges due. They see the check engine light that won't go away after reset but they can't find anything wrong, all voltages and parameters are within spec. I took it back to the garage twice and they can't get it to do it's weird mis-fire thing. You can't feel any rough engine idle or power lose. After I reset it the car runs fine and it won't not even do it's little rough/loose of power thing but the check engine light will come back on in about 15 minutes. The only code it reads is P300 (random Mis-Fire). The check engine light begins to flash and then turns solid and stays on until I reset it with my code reader. Pushing in the clutch and tapping the throttle seems to help clear it up. Here is the weird thing, it goes away as quickly as it came on. The car will be running just fine when out of the blue it will loose power and start running rough like a severe mis-fire. Just after I got the car back it started to do a weird thing. I had the timing belt, tensioners, waterpump, spark plugs, crank seal, & valve cover gasket replaced by a local garage with an outstanding rep. I bought this car new and have never had any problem with it until now. I have a 2002 Mazda Protege 5 that has 96000 miles on it.
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