Rep Power: 219

Okay, first things first. 02 civic ex coupe, 1.7L SOHC Vtec, 150 comp. acrossed the board, full leak down test confirms. MODS: Short ram intake, Performance valve springs, Cat back HKS exhaust, 50 shot nitrous.

When I start my car after its been sitting for a few hours, and its cold outside, my car misfires in the 4th cylinder and my CEL comes on. Codes are, 4th cylinder misfire and air fuel metering. I replaced my MAP sensor as a caution, along with my plugs.I had a crack in my exhaust manifold, so me thinking maybe the 02 sensor was reading incorrectly I tossed my aftermarket header, and threw my stock one back on. Didnt help... Still got rough idle cold, and CEL with misfire. Wondering if maybe it could be my intake manifold gasket? Even though, when I replaced my head gasket, the fel-pro kit came with one and I replaced it then! What do you all think it is? Anyone have these issues before? What was the cause, and what was the solution? Got multiple people telling me multiple things, but would like to know someone that has had the issue and fixed it. HIT ME UP!!!

 
Rep Power: 812

could be ignition coil, did you check all of their resistance and see if they are similar? could also be clogged cat converter which can cause misfires and generally poor engine performance.

 
Rep Power: 219

Okay quick update... I pulled new OBDII codes, and now im having multiple misfires in all cylinders! Total frickin bummer. How do I know if my cat is clogged? Cause once the car is warmed up it runs fine. Just on cold starts. I am wondering if the heating unit on my O2 sensor is done? That would cause misfires on cold starts and work fine after warm up right? Checked the coils, and all of them spark. Im starting to get frustrated. Its not the manifold gasket either, cause I sprayed carb cleaner all around and on the manifold to see if I had a vacuum leak and my rpm's did not studder one bit! Thanks for the advice Gearbox, but I seriously wish I could find a solution!

 
Rep Power: 812

this is very hard to figure out. i would normally say headgasket, cause i had the same problem. cold starts would be rough because coolant leaked in the cylinders, but once the engine warmed up and burned it away, it ran fine. have you checked the exhaust for any sort of white deposits, or the plugs? if the tips are white, its the headgasket again. i know you just replaced it, but did you get the head looked at before putting it back? otherwise it could be slightly warped and would just blow the gasket again. i know your comps were all fine, but a small headgasket leak will not be detected. my comps were all high and the same too, even with the small leak in the gasket. and no coolant mixed with oil. do you burn coolant at all? even if its a small amount over a weeks time. have you cleaned the IAC valve yet? cause thats what allows the car to idle and slowly decrease the rpms as engine warms. but if its stuck (until hot coolant warms it up), then it cant properly keep the engine at idle. have you tried starting the car with the primary oxygen sensor unplugged? if the sensor is the problem, the car will run fine without it plugged in. also you can test the sensor heater by turning the car to ON position (do not start engine), waiting 30-60 seconds, then feeling the sensor with your hand. it should be warm to the touch, or at least warmer than surrounding metal. wipe the sensor off afterwards so the finger oils dont ruin it.

 
Rep Power: 219

Hey, thanks for all your input Gearbox! First thing, I had the head planed and leveled out at a machine shop before I put it back on. So I know thats not the issue. No coolant leak, no coolant in the oil. But I have not touched the IAC valve yet! Probably try that this weekend! As well as the O2 sensor tests! Again man thanks tonz for your input! If I could give ya more rep I would!

 
Rep Power: 812

no prob, yeah it prolly is the iac valve. they need to be cleaned out at least once after the engine breaks in (around 20k miles), then they stay pretty clean. use lots of carb cleaner and qtips, and be careful getting out those philips screws. they tend to strip easily. use the right size bit and put alot of force on it. worst case you gotta drill them out and get new screws.

 
Rep Power: 0

still having problems with this or no?

 
Rep Power: 219

Yeah unfortunately... I took it down to my local checker so I could get the codes read again and clear em, but what is wierd is, a week ago I took it down to autozone and it said I was misfiring radomly in all cylinders, and yesterday when I took it to checker, it said I was only misfiring in cylinder 1. :{ I dont get it... First time the CEL come on it said cylinder 4! That was about a month ago! Its killing me! Checked the o2 sensor, and its not that, still havent done anything with the EGR yet, maybe this weekend if it aint freezing *** cold outside. Im wondering if maybe I need to do a valve adjustment? Cause after I changed my head gasket I did a quick valve adjust, but Im starting to hear them click again, so maybe that needs to be done. Would that cause misfires? Anyway, need some more help, so if ya got some suggestions my fellow Korean, then I would gladly listen!

 
Rep Power: 219

Okay quick update... My Battery took a crap on me today when I was getting ready to leave work. Im wondering if it just wasnt giving enough juice to certain components and making them not work properly. No light yet and I've driven it twice since I left work sooo, we will keep our fingers crossed.

 
Rep Power: 0

Keep an eye on it. If it's not mech then maybe your ECU is starting to crap out. I just had to replace mine and get Honda to retune it. So new battery and everything checks out?

 
Rep Power: 0

also sorry for the late reply I've been busy working on the supra.

 
Rep Power: 219

Well, so far, so good with the new battery! Maybe I just had a crappy battery that was unable to maybe keep the fuel pump moving properly or something... I dont know, but the CEL hasnt come back soo, horray!
So ya got a Supra huh! Gotta love a car that can handle 22 psi on stock internals!!!

 
Rep Power: 0

Yes sir! Heh I <3 my supra. I'm just on this forum for support on my Civic. I'm glad I did because there is alot of guys on here that are really willing to help. I think if it wasn't for gear box I would have pushed my civic off of a cliff because of the issue's I was having.

 
Rep Power: 219

LOL, I hear ya! Im going to college to be a tech, and still have issues troubleshooting! And I have taken my vic to the edge of a cliff more than once!