Rep Power: 0

2002 Honda Civic DX 1.7 5spd

Just did timing belt and it ran perfectly fine for the first day. Today now it is misfiring randomly. It'll be idling and will pop occasionally. Itll sometimes pop twice in a row, other times itll pop once. And its randomly every 3-6 seconds or sometimes more. Driving it on the road it still has good power, but when you let off the gas and start "engine braking" itll start popping. Its straight pipe so it can pop but it was only popping before if you hit 5k rpms and shifted. Now it pops when you engine brake anything above 2k rpms. So it "misfires" on idle and engine braking. Any ideas? Doesnt hinder it at all when accelerating... Id assume spark plugs or coils but want to know if maybe its something else. Or if it is one of those two how to tell which one it is specifically. Its not throwing any codes... Just misfiring... Funny thing is my upstream o2 sensor was disconnected. I reconnected it when I saw it after replacing coil boots and now this...

 
Rep Power: 367

coils very rarely fail

 
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Was looking up why theres oil on the spark plugs... Said something about valve cover gasket? Could that be my issue? Oil on plugs so I need new valve cover and spark plugs?

 
Rep Power: 125

What engine codes are you getting?

That exhaust certainly isn’t doing you any favours.

 
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None. Had P0135 but that went away when it was plugged back in. I had P1456 evap code but cleared that... Doesnt matter id assume...

Took out my spark plugs and this is what they look like. They are Denso plugs

 
Rep Power: 367

put new plugs there. they look wasted even if the electrodes look fine. put a new gasket while at it. consider getting a proper exhaust

 
Rep Power: 0

You think this might possibly be my miss?

Also for exhaust... As in put a muffler on for backpressure or a cat as well?

 
Rep Power: 367

bringing thing as close to as they were supposed to be is in basic machine and product rebuild.
you go outside of it, everything not at spec is suspicious. If you dont want the hassle, keep it stock.
if you don't want to troubleshoot something outside of spec (you need to do your legwork and check, test, check, think what is wrong, check, test, etc) don't mod it.
I had the car up for 2 weeks, everyday tightening the tool a little more bit more until the ball joint finally banged out so i could finish the work

 
Rep Power: 222

Timing is probably out a tooth or two, new spark plugs are certainly a good idea.

And put a proper exhaust on so your neighbours don't hate you

 
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I don't believe so. Instructor said its in time and it started a the first turn of the key. Had no issues starting and wasn't missing until the day after.

 
Rep Power: 222

So it ran fine with the primary o2 disconnected, and with it connected now it runs bad?

 
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Yeah. With it reconnected now its misfiring. But still no check engine codes

 
Rep Power: 125

That sensor is probably crap, I’m going to guess aftermarket?

 
Rep Power: 222

Put a new one on, buy Denso, don't cheap out

 
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Not sure. I didn't put it on lol

Didnt even think about it. I'm gonna disconnect it and see what I'd does.

 
Rep Power: 210

The timing belt may have skipped a tooth between the day of initial install until the the issue started. Only way to verify that is remove the timing cover, head cover, and inspect marks on crank's timing gear and the cam's timing gear..

 
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So you can do everything right and it still jumps... Thats a big welcome to Honda... Anyhow besides this I did a leakdown test and the coolant was coming out of radiator so its taken apart for head gasket. At 208k I'm not sure how worn the motor is but I may just put a new gasket and some new spark plugs and call it a day. See how long it lasts. Hopefully like a year...

 
Rep Power: 367

are you loosing coolant from the reservoir?

 
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I don't believe so. Its the radiator I was topping off everytime I went under the hood. And it was the radiator that was overflowing with the leakdown test.

 
Rep Power: 367

then why are you saying you going to change the headgasket? Work on the radiator and hoses...

 
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because... the radiator was overflowing when I was doing leakdown test... Doesnt that say its a head gasket? I was putting air pressure into combustion chamber yet it was coming out the radiator... Isnt that what you say would be a head gasket?

 
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Not really sure to be honest... May just throw a new gasket on (Without milling head due to long wait times in my area) and just hope for the best. Worse case scenario it blows in a few months or hopefully more and just throw a low mileage motor in

 
Rep Power: 367

while running the car, the coolant is sent to the reservoir. if breached headgasket, the coolant reservoir gets full and leaks coolant from there.
If your reservoir is not full and leaking, there are less chances that the gasket is breached.
If the radiator or hoses are leaking, it might not be the gasket.

is this the test you did?

 
Rep Power: 0

Thats what I did. Mine didnt bubble tho. It just slowly raised up and up til it went over the edge of the radiator

 
Rep Power: 367

OK, that clears it.
if you have a breach, it might not be big (If yes, it would lose coolant from the reservoir/reservoir would be full in normal operation.
you can change it (it might be small, but might be needed in the future).
No leaking radiator or hoses expected. Leave changing the radiator out for now.

PS: My reservoir was full and losing coolant for 6 months. I drove back from Quebec to TN and it never overheated (I would often check and fill during those 6 months) - it is not urgent, most take a long time to breach if taken care of and checking the reservoir/radiator levels. It's gonna happen, but nothing explosive all of a sudden. As long as you check levels in radiator and reservoir and the temp needle.

 
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Just dont have the money for a head mill right now... Gonna replace the gasket and fingers crossed hope it holds for a good while. Wasnt overheating before but wanted to change just incase... If it can last like 6 months ill be able to either get a new heard or mill it. Or maybe ill just be lucky and it was only the gasket. Only issue being is I really cant tell if it actually got to any of the coolant jackets on the gasket... But it looks like it leaked between cylinders. Good thing it only took 3 hours to remove head first time. Next time should take 2 hours id assume or less.

 
Rep Power: 367

keep as is
do later
check radiator and reservoir levels daily

mine was already losing coolant from reservoir and then 6 months. if yours is not losing coolant from reservoir, you might have more time

if it suddenly loses more coolant, it's time

 
Rep Power: 0

Will do. Either way I love this car so far. Handles amazing compared to my recent vehicles. So I wont give up on it, if it blows ill just swap a new engine. Just want some coilovers and a decent exhaust (That isnt straight piped) and ill be a happy man lol

Thanks for the help guys! Still open to comments on this thread if you have anything else to add that I might not know about.

 
Rep Power: 210

Yes, you confirmed the head gasket breach.
Why go through the work and expense of replacing the head gasket if you aren't 100% sure the head is flat within specs (under .004")?
If it ever overheated the head is most likely warped. You will have the same issue and will need to redo it correctly to fix it properly. Also, only use a Honda Genuine head gasket.

Watch the video below if you want to try to sand the head flat yourself

 
Rep Power: 0

Because the breach was very minimal. It runs quite cool honestly. Just was gonna do it for preventative maint but turned out I have my eyes set elsewhere. I just got the block back together and its running a solid 170F. It might weep some coolant but honestly I'm not too worried. Heck I'm not even sure if it is leaking coolant yet. It seems to be running better as of right now. Just need it to last a few months so I can grab a vtec head since my head is a non vtec. And even if it blows early I can just keep driving my Chevy Blazer.

TLDR I thought I wanted to fix it to save this head but a friend showed me VTEC heads I should save for.