Misfire on 98 Mazda Protege

Hey guys,

About two weeks ago I noticed the engine idle start to hesitate but ONLY while idling. I was sort of leaning towards the distributor cap or rotor but that didn’t add up because in the past when either of these would go out the car would just die without any warning whatsoever. So I just kept driving it and then tonight when I started the engine it was hesitating a lot more than it had been and also hesitating during acceleration but would smooth out after I would reach and maintain 40mph. The CEL also started flashing on and off. I went ahead and replaced all the spark plugs, distributor cap and rotor with no improvement. Tomorrow I plan to replace the plug wires. The code it’s sending is P0302 (misfire cylinder 2). If the plug wire doesn’t do the trick and I can’t find any leaks on the intake I’m going to try to figure out how to inspect the ignition coil (well, it shouldn’t be too hard to figure out since I have two different shop manuals for this car.) Another possibility for P0302 is low engine compression but I seriously doubt that’s the problem because last time I checked the compression all 4 cylinders had above average compression. I doubt the plug wire is going to fix it since the wires only have about 20k miles on them and I don’t think I have any leaks on the intake so I decided to come here and see if anybody has any suggestions as to where else I should look? Oh yeah, just remembered. I also put a stethoscope (actually a screwdriver) against the fuel injector for cylinder number 2 and it was clicking away just like the other 3 injectors so I guess the injector isn’t the problem unless it can be faulty and still make the clicking noise. So should I check the injector with a meter or is the clicking enough evidence that it’s working fine?


please give me YOUR definition of above average compression

I owned a 1997 Protege for many years . . . same body style and engine as yours, so I’m not talking smack

Proper valve lash is crucial on this engine, and if it’s tight, it will lead to low compression and hard starting

Tight valve lash can also lead to burnt valves, misfire, and all sorts of bad

I own a genuine mazda factory service manual for this car, so let me know if you need any resistance specs or anything like that. For the coil or injectors, for example

Do you have the means of performing fuel pressure tests . . . in other words, do you have a gauge and the ability to tee into the system, because I know for a fact there’s no fuel pressure test port on your engine

Are you using exactly the plugs listed in the owner’s manual?

Are they gapped correctly?

I hope you’re not using those generic 4 electrode plugs

Do all of the wires securely click onto the plug and the coil. I’ve seen a few wires and coil towers so corroded, that you couldn’t get a good connection, leading to a misfire

Do you have an extremely blue spark using the spark tester, on all of the wires?

1.5 or 1.8 . . . ?

Can you swap # 2’s plug wire with one of the other wires & see if the misfire follows the wire ?

He’s already planning on a new set of wires tomorrow

That’s why I personally didn’t mention that

220 on three of the cylinders and 215 on the other one. The manual says something like they should be at 190psi. And I already took care of the valve clearance a few years ago, actually with a lot of help from this forum.

I can rent a fuel pressure gauge but how should I T in if there’s no place to do so?

I’m definetely using the right plugs, they’re OEM.

I’ll check to make sure the wires are securely connected.

I do have a spark tester so I’ll check that tomorrow as well.


Those are good compression numbers . . . that’s assuming those numbers are from now, not from a few months ago, for example

I’d concentrate on those new wires and spark before worrying about fuel

Glad to hear you’re using OEM plugs . . . what about the gap?

I would at least measure the resistance of the injector before calling it good. At least make sure it’s correct

If that set of new wires doesn’t fix it, we can explore other possibilities, such as fuel, at that time

There is the possibility that an injector is partially plugged, but to actually verify it involves teeing in that fuel pressure gauge and hooking up an injector balance tester

Can you hook up a vacuum gauge at idle?

The plugs come already gaped.

Yeah, I have a vacuum gauge that I can hook up. What numbers should I look for?

Whoops, just noticed you asked… it’s a 1.5 liter.

For future reference, a blinking CEL indicates you need to stop driving to prevent damage to the catalytic converter.

All fixed. It was the plug wire. I put a new one on and it purrs like a kitten. Although I’m not convinced that the old wire is bad. I think it wasn’t making a good connection. Somehow the connector up inside the boot is really deep in there and especially compared to the connector in the the new plug wire boot. And when I push it onto the plug I don’t feel the firm connection like I do with the new one. Whatever the problem was I’m just glad it’s fixed.


Thanks for the update , glad it was an easy fix .