Mechanics

RANDOM MIS-FIRE CODE

2002 Mazda Protege

Engine Performance problem
2002 Mazda Protege 4 cyl Front Wheel Drive Manual 96000 miles

I have a 2002 Mazda Protege 5 that has 96000 miles on it. I bought this car new and have never had any problem with it until now. I had the timing belt, tensioners, waterpump, spark plugs, crank seal, & valve cover gasket replaced by a local garage with an outstanding rep. Just after I got the car back it started to do a weird thing. 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. Here is the weird thing, it goes away as quickly as it came on. Pushing in the clutch and tapping the throttle seems to help clear it up. The check engine light begins to flash and then turns solid and stays on until I reset it with my code reader. The only code it reads is P300 (random Mis-Fire). 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. You can't feel any rough engine idle or power lose. I took it back to the garage twice and they can't get it to do it's weird mis-fire thing. 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. They even had the car for two weeks but just gave up on it with no charges due. They said bring it back when it dies or is just about to, it would be easier to find the problem then. After driving it like this for a few weeks a new code has come up for " bad warm-up catalist". Which tells me the cat converter has gone south due to unburnt gasoline from the mis-fire getting into it. I'm completely lost at this point, what should I look at to cure this problem? EGR valve, Ignition coils, etc?
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Protege5iniowa
December 20, 2008.



Hi Protege5iniowa,

Random misfire is always a troublesome problem to resolve as there are many possibilities. Since problem started after timing belt replacement, I woud suggest checking the CMP first.

DTC P0300: RANDOM MISFIRE DETECTED

Condition

PCM monitors Crankshaft Position (CKP) sensor input signal interval time. PCM detects a misfire in a specific cylinder by calculating change of CKP interval time for each cylinder. 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. 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. This is a continuous monitor. MIL is illuminated when PCM detects malfunction during 2 consecutive drive cycles. Possible causes are: Camshaft Position (CMP) sensor malfunction.
Crankshaft Postion (CKP) sensor malfunction.
EGR system malfunction.
Excessive air leak in intake-air system between Mass Airflow (MAF) sensor and dynamic chamber.
Fuel line leak.
Fuel pressure regulator malfunction.
Fuel pump malfunction.
Ignition coil malfunction.
MAF sensor malfunction.
PCV valve malfunction.
Plugged or restricted fuel filter.
Plugged or restricted fuel line.
Poor connection or wiring problems.
Poor fuel quality.
Purge solenoid valve malfunction.
Secondary ignition system malfunction.
Vacuum hoses damaged or improperly connected.

Diagnosis & Repair Procedure

1. Turn ignition off. Connect scan tool to DLC-2. Turn ignition on, engine off. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Check service bulletins for repair information related to this DTC. If repair information is not available, go to next step. If repair information is available, perform diagnosis and repair as necessary. After repair, go to step 21.

2. Turn ignition switch off and then start engine. Using scan tool, check for DTCs. If no other DTCs are present, go to next step. If DTCs are present, go to appropriate test.

3. Using scan tool, access ECT, IAT, MAF, RPM, TP and VS PIDs. Start engine and run at idle. Ensure all signal data is within specification. If all PID data is within specification, go to next step. If any PID data is not within specification, go to applicable test iand go to step 21.

4. Referring to FREEZE FRAME DATA, operate vehicle under same conditions as when DTC was set. Record PID data for ECT, IAT, MAF, RPM, TP and VS. If all PID data is within specification, go to next step. If any PID data is not within specification, go to applicable test. Diagnose and repair as necessary and go to step 21.

5. Check CMP sensor operation. If CMP sensor is operating properly, go to next step. 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.

6. Check CKP sensor installation. Repair as necessary and go to step 21. If CKP sensor is not loose, go to next step.

7. Start engine and allow to idle. Check ignition coil operation at each cylinder with timing light. If timing light flashes at all cylinders, go to step 10. If timing light does not flash as specified, go to next step.

8. Disconnect ignition coil 3-pin harness connector. Turn ignition switch on. Measure voltage between ground and ignition coil 3-pin harness connector terminal " A" (Black/Blue wire). If battery voltage is present, go to next step. If battery voltage is not present, repair open in Black/Blue wire between ignition switch and ignition coil 3-pin harness connector terminal " A". Go to step 21.

9. Check ignition coil resistance. If ignition coil is okay, go to step 21. If ignition coil is faulty, replace ignition coil and go to step 21.

10. Start engine. Using scan tool, access MAF PID data. Depress accelerator pedal to Wide Open Throttle (WOT) and release to race engine. MAF PID voltage reading should respond quickly with engine RPM. If MAF PID response is as specified, go to next step. If MAF PID response is not as specified, replace MAF sensor and go to step 21.

11. Check for vacuum leaks in intake-air system between MAF sensor and throttle body. Also check for vacuum leaks at throttle body and dynamic chamber. Repair or replace as necessary and go to step 21. If no problem is found, go to next step.

12. Check fuel line pressure. If fuel line pressure is okay, go to step 16. If fuel line pressure is to high, go to next step. If fuel pressure is to low, go to step 14.

13. Disconnect vacuum hose from fuel pressure regulator. Start engine. If vacuum is present at hose, check fuel pump maximum pressure. Check fuel return hose for clogging or restriction. If no problems are found, replace fuel pressure regulator. After repair, go to step 21. If no vacuum is present at hose, check hose routing. If hoses are okay, replace Pressure Regulator Control (PRC) solenoid valve and go to step 21. If hoses are misrouted, repair as necessary and go to step 21.

14. Check fuel pump maximum pressure. If maximum fuel pump pressure is 64-92 psi (4.5-6.5 kg/cm 2 ), go to next step. If maximum fuel pump pressure is not as specified, repair open or poor connection in fuel pump circuit. If fuel pump circuit is okay, replace fuel pump and go to step 21.

15. Check for leaks in fuel system from fuel pump to fuel rail. If any leaks are found, replace leaking fuel line and go to step 21. If no leaks are found, check for restriction at high pressure fuel filter and foreign material at low pressure fuel filter. If restriction is present at high pressure fuel filter, replace high pressure fuel filter. If foreign material is found in low pressure fuel filter, clean fuel tank and low pressure fuel filter. If fuel filters and fuel tank are okay, replace fuel pressure regulator and go to step 21.

16. Check engine compression. Engine compression should be a minimum of 119 psi (8.4 kg/cm 2 ) at 300 RPM with a maximum variation of 28 psi (2 kg/cm 2 ). If compression is as specified, go to next step. If compression is not as specified, repair as necessary and go to step 21.

17. Turn ignition switch off. Disconnect both hoses from purge solenoid valve. Purge solenoid valve is located at rear of engine compartment. Blow air through purge solenoid valve. If air does not flow through valve, go to next step. If air flows through valve, replace purge solenoid valve and go to step 21.

18. Check PCV valve operation. Replace as necessary and go to next step. If PCV valve is okay, go to step 21.

19. Remove EGR valve and ensure valve is not stuck open. If no problems are found, reinstall EGR valve and go to next step. If EGR valve is stuck open, replace or repair as necessary and go to step 21.

20. Check cooling system for combustion gases. If no problem is found, go to next step. If combustion gases are found in cooling system, repair leak and go to next step.

21. Reconnect all connectors. Turn ignition switch on. Clear DTCs. Start engine. Using scan tool, perform DRIVE MODE 1 - PCM ADAPTIVE MEMORY under SELF- DIAGNOSTIC SYSTEM. Check for DTCs. If DTC P0300 is present, replace PCM and go to next step. If DTC P0300 is not present, go to next step.

22. Cycle ignition switch from off to on. Check for DTCs. If no other DTCs are present, testing is complete. If any other DTC is present, go to applicable test and repair.

KHLow2008
Dec 22, 2008.
Check your coil packs where they connect electrically via a spring to the spark plug directly under the coil (the connection to the coil pulls off easily). I have a 2001 ES and the contact between the coil pack and this spring was badly oxidized, causing loss of ignition on 2 of 4 cylinders. The car exhibited exactly the symptoms you describe, including the P0300 code. Cleaning the contacts fixed the problem, but unfortunately for me my catalytic converter had a melt-down from raw gas igniting in it before I traced the problem to this area.

Tiny
Kmhammer1
Feb 24, 2009.
I agree with the coil pack, mine did a similar thing randomly, luckily I had the hood up checking things out when I heard the spark jump from one of the coil packs. New coil pack took care of the problem.

Tiny
Popawalker
Feb 27, 2009.
I have had this same nightmare for a year now. I have a Mazda Protege LX 2002. Had EGR replaced, warm-up CAT replaced, 4 fuel injectors replaced, complete tune up, sensors all fine, MAF checked, coils checked, PCV replaced, fuel pump checked, plus a dozen more things done to it with no complete cure on the random misfire code P0300. Today at a new shop they just found that my fuel regulator line was not connected(random misfire) & pretty much had caused my new warm-up CAT to die again(P0421). So now I am back at the old shop to have it replaced again & they are paying for it since it was under a year since I had it done. I am praying that this time I will be free of this crapolla. At least we went from P0300 to P0421. I will let you know if it cured my nightmare.

Tiny
Angelinacarroll
Mar 21, 2013.