IGNITION PROBLEM : Engine misfire P0302 code

RAFAEL LOY

MEMBER
2000 MAZDA PROTEGE
1.6L
4 CYL
2WD
AUTOMATIC
136,800 MILES

So under a load the car misfires and shakes, especially after the engine is warmed up.

2. We checked the spark plugs, they all seem good. I put in new coils like a year ago (used though).

3. The car burns oil (white smoke when you first start her up).

4. I tried to check the resistance on the coil terminals with a multi-meter. I only got like 1KOHM on both coils, but I doubt both coils would go?

What should I do next? I do not want to throw parts at a car.

6 Replies

AL514

MECHANIC
4,701 POSTS

It looks like P0302 is cylinder number two misfire. You can try a couple things. Switch the spark plug and fuel injector to a different cylinder and see if the problem follows to a different cylinder. You may have a bad fuel injector. You should get another code following the misfire. Code P0301 to P0304 are cylinder 1-4 misfire codes. If no change from that cylinder you may have to do a compression test and cylinder leakage test to see if a valve is not seating right (weak valve spring etc), anything messing with compression on that cylinder. Also, just keep and eye out for any vacuum leaks while you have things apart, hope this helps.

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Thursday, November 10th, 2016 AT 11:20 PM

RAFAEL LOY

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3 POSTS

Actually the code changed from 304 to 302.I know the coil was swapped from cyl 4 to cylinder 2, but apparently my mechanic also swapped plugs at the same time.

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Sunday, November 13th, 2016 AT 4:24 PM

AL514

MECHANIC
4,701 POSTS

Well atleast its narrowed down to either being the plug or coil if the codes changed with the switch over in cylinders. Switching the coils to a different cylinder is very easy. You might just try switching them around again and leave the plugs where they are this time. Was your mechanic not able to determine what the problem is?

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Monday, November 14th, 2016 AT 10:13 AM

RAFAEL LOY

MEMBER
3 POSTS

Its the coil. But I replaced both coils (with a used one) two years ago. Why would they be defective after two years? (The plugs are good).

Thanks for the help.

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Tuesday, November 15th, 2016 AT 1:00 PM

KEN L

MASTER CERTIFIED MECHANIC
47,722 POSTS

Yes this can happens easily, coils are a high failure item, replace all the spark plugs with new and the failed ignition coil. If the same coil fails again replace the fuel injector. If the fuel injector spray pattern is weak it will overload the coil.

Let me know what you find.

Best, Ken