I have a 98 Civic EX with over 240000 miles on it.

It has an cylinder 3 misfire for over a year now. About two months ago we changed plugs, wires, distributor cap and rotor, fuel injector #3, new fuel pump, and ignition coil (timing belt was put on about 3 years ago) My buddy did a "ghetto" timing belt test and did a "ghetto" cylinder test. I'm not a car whiz. He had me try to crank the car with the spark plugs out. That is what I mean by "ghetto test" I don't remember how he checked the timing belt without removing any parts, but he said he did. We put on a new fuel filter about four years ago. Not throwing my buddy under the bus. He went to automotive school for what it's worth and has done fantastic (super affordable) work on my car for nearly a decade. This is the first time he has not been able to solve a problem.

The misfire comes and goes all day. Sometimes the check engine light goes out for a couple of days. The car runs smoothly for maybe 30 minutes, then it starts misfiring. Then it's smooth again. It goes back and forth all day, runs pretty smooth on the highway 70% of the time but almost always misfires going up hills on the highway. And then the check engine light comes on again with the cylinder 3 misfire code. A few days later the light goes back off. All of this happens over and over.

I know my catalytic converter is pretty much toast. I used to get a catalyst deficiency code and O2 sensor code that started years ago, but since we stopped testing emissions here, I did not get a new cat.
The codes for the cat hardly ever come up anymore for some reason.

The one did I have not changed is the distributor itself. Only the cap and rotor were changed. The rotor looked pretty bad if I recall.

I don't know if it's relevant but all of this started after we had a very bad freeze here in the south winter of 2023. It almost never gets that cold where I am at. Everything was frozen. After that the car was never the same. Before the freeze it ran perfectly. A couple of days after the freeze it wouldn't start at all. My buddy finally got it going and it was instantly misfiring and has never stopped since that day. He did the plugs, wires, cap and rotor back then also. At one point a week later it misfired so horribly I could barely get it home. It has never misfired that bad again but we can't get it to stop.

We tried someone's recommendation about checking some fuses, but my diagram didn't seem to match up with what a guy on here said about the same model car. My buddy didn't find anything wrong looking with the fuses that he did check.

I wouldn't think that a bad cat would make the same 3 cylinder misfire and no other ones. Seems like the problem would be widespread.


Thanks in advance for not calling me dumb. I know you're not supposed to drive a misfiring car, but I'm poor and have been able to drive to work and make a living for a year and 3/4ths' now as opposed to not driving the car and not being able to get to work all that time.

Lastly, sorry about the super long letter.
Now I'll shut up and hopefully learn something that might help.

 

Well since it's been over a month and nobody replied, I will say that I am even more puzzled as the car has now been running trouble free for about five days. Usually it only runs right for half a day at most.
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Well 5 months gone by and not one person has a comment for me? Anyone? I would even take a loving pi$$ off at this point.

 

Have you checked wiring going to injector?

 

Sorry I am a little car dumb. So you don't mean the spark plug wires right? But the injectors wires? No I don't think those have even been replaced or checked. We just put a new injector on cylinder 3 but did not change the wire. My mechanic friend said he doesn't see why that wire should be a problem but I imagine anything can mess up.

 

While the engine is running, try moving around the wiring harness, try shaking various plugs, touch all of the sensor connectors and ensure it's not random vibrations causing a loose connection to give intermittent signal. Make sure the engine control computer is mounted securely and the wires aren't getting pinched/kicked/hit by things. Make sure you have good ground points that contact bare metal, and not paint. Make sure you have all the grounds, and they are in good condition. I assume you have a Haynes manual or similar to help you.

Inside the distributor there is an ignition coil. Test it using a multimeter. Temperature changes can affect the resistance and the strength of the spark generated.

 

Get someone who knows how to use a multimeter.

 

Will do. My mechanic friend has one.

 

Thank you for these suggestions. I will try them out tomorrow.

 

Should see a pulse at the plug.

 

Your mechanic friend should have done a compression test months ago... I would start there. You mentioned that you are "poor"... unfortunately, this is not a good excuse for failing to perform proper auto maintenance... you just have to prioritize. One cannot assume that replacing old parts with new parts will solve the issue just because you used "new" parts... the cheapest replacement parts that you can find are ALWAYS of substandard quality and they may be just as bad as the worn out parts that you replaced. Quality replacement parts increase the chances that you fix what you replaced if in fact that component was your issue.

The method I would use to be "budget friendly" would be to work with a friend/acquaintance who has a good running car with a similar engine... and try swapping his "known good" parts in place of yours to TEST whether each of these items will solve your problem. "Throwing Parts" at a car doesn't make one a mechanic... being able to diagnose your issue and work through a comprehensive plan/process to eliminate possible issues and zero in on the actual problem does.

 

How did the number 3 cylinder spark plug look? Did it have oil on it? I get a very occasional misfire on my B16 which I'm thinking is the valve stem seals allowing oil to enter the cylinder, coating the plug and causing the misfire.