Rep Power: 0

Hey y’all

So my civic has had a misfire for about a month now.
Originally threw a code for a misfire on cylinder 3. Changed the spark plugs, and went away for a couple days. Came back, I used the help of A neighbor who is a mechanic, and we did some trouble shooting. Compression on all 4 cylinders were good, fuel pressure was good. And we ended up looking at the timing belt finding that some teeth were missing, replaced the belt and re timed the engine and ran great for a day and is now missing again. And it now misses at idle cold and sometimes when warm. Also when driving. I checked all ignition coils and they all were giving a good spark. What should I check/Change next?

 
Rep Power: 223

The timing belt was missing teeth?!?! Sounds like you're lucky to have a running engine at this point.

What kind of spark plugs did you use? Hopefully NGK Iridium plugs. You can also try swapping the coil pack with a different cylinder to see if the misfire follows it. Another possibility is clogged EGR runners, those can cause misfires on these engines.

 
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Those are the plugs I put in it. So I finally got another code today, for a miss on cylinder 2. Which is what I changed the coil from cylinder 3 into. Note I changed these about a week ago. And it’s been missing Off and on the entire week. My neighbor and I put new boots and springs in the plugs today, and started it up, and it missed right away. I’m gonna clean out the egr next. If that doesn’t work, should I go to buying a new coil?

 
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Update. My car doesn’t have an egr as it is a 03 with a 5 speed. Or at least I can’t find it.

 
Rep Power: 223

The EGR valve is on the passenger side of the valve cover (if equipped). From what I've heard it seems to be random which Civics have it. I have had around 7 Civics this gen and all have had EGR. Some of them are sedans, some coupes, some auto, some manual.

If you moved the coil pack from cylinder 3 to cylinder 2 and the misfire moved as well I would start with replacing that coil pack.

 
Rep Power: 209

Did you guys inspect the timing belt auto-tensioner spring or for free-spin (bearing)? A new belt won't help if there is an issue with the tensioner.

 
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The belt, water pump and tensioner were all replaced. And inspected. I got a P0300, P0302 and P0303 code today. I don’t think a single coil is the issue anymore. Should I check the fuel line, and check the pressure on it? The misfire is more often, and is almost constantly at idle but sometimes it goes away. Even at idle.

 
Rep Power: 125

It almost sounds like a vacuum issue.

 
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So I cleared the CEL, and it came back with only a PO302 today, I’ve driven the car maybe a whole 10 miles during this time just so I can get codes. I’m driving the car home today with the same PO302 code and the CEL started flashing, I’m getting it towed home by a buddy. I have no clue what to do next. Any advice?

 
Rep Power: 125

Burn it

In all honesty, I'd just drive it and monitor it closely. If the plugs aren't covered in oil or leaning out, and it's driving okay (I understand it's misfiring but I'm assuming it still has enough power to drive safely), then I'd just drive it.

 
Rep Power: 209

check valves clearances and do a compression test on it. Leakdown test would be preferable if you have the tools.

 
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I have the same issue rn with my 02 civic ex

Changed my Spark Plugs because my old ones were thrashed. I start getting this missing at idle.
I put fuel injector cleaner to ease of some of the missing but it still pertains.

What do I do ?

 
Rep Power: 223

Have you done all the troubleshooting we gave above?