Hello, I have a 96 civic with a 96 integra engine in it, B18 non v-tec, and I am having an issue with random misfires on all cylinders (when looking at the codes, its pretty random on what cylinder misfires {It will be cyl 1 then clear codes, and next it will be 4, or 3 ect.}). The car/engine runs good, but I get a random misfire code at idle, i can feel/hear the misfires (the occasional buh buhh noise). Which to be honest I dont really care about since its only at idle and they are just so slight, and the car runs and drives great besides that. But I am having the issue, that my emissions is due in a few days, and I have been trying to figure out this misfire and I cant, which is why i made this post, i dont really like asking for help, but I dont really have any other ideas at this point. The random misfire check engine code is preventing it from passing, and I know the car will pass if I can just get that code figured out.

Things I have tried is, cleaning battery terminals, swapping different distributor cap, cleaning cap and rotor, new spark plugs/wires, tried looking for a vacuum leak with carb cleaner, but didnt seem to find/see one. Car has great compression. I feel like its something stupid and small but idk.

I tried pulling out each plug wire while the car is running, and got the expected drop/change in rpm, same with each injector. So i know its just not one dead cylinder. Its a random misfire that switches cylinders, at least the scanner will throw a code for every cylinder after a while, but it does seem like it throws the 1 and 3 cylinder codes the most.

The car is idling around 730-750 rpm when hot (is that a bit low?), but closer to 1100 when cold start. I was gonna try and bump it up so it was around 800 but I was taught to never mess with idle screw and it should be avoided at all costs until you know there arent any other problems.

To be honest, im pretty crappy at finding and diagnosing small issues like this, I just dont know what else to try/check. I can do repairs, and replace parts, but I just dont know what else to do or look for, thats why im making this post. Any help, or insight, or ideas, is greatly appreciated. If you need some more information, i will try to do my best to provide it.

PS.
I have until the end of the month to get the car to pass, (6 days)

(edit) Tomorrow im going to try and change the rotor, after thinking about it, its the only thing i havent switched out yet.

 

What ECU are you using ?

 

Im using the ecu that was in the integra the engine came out of, I dont know the model of it off hand, i will look at it tomorrow

 

P75 ecu. But I ended up getting it to pass this morning, I just cleared the codes in the parking lot at the testing place, and LUCKILY light stayed off long enough to get a pass. Light came back on as soon as I was pulling out of the parking lot ha. Im still gonna try to get the light/code taken care of, but its not an emergency anymore, which is a huge load off my shoulders ha. Went to pick up a new rotor today, and just got the cap and rotor set as it was just a couple dollars more. Installing tonight, will update if it takes care of the code/s or not. I hope it does.

 

Did not get rid of the code lol. Thought i was good, but came back on after 10 mins. have a spare distr, so I swapped out all the guts while I was changing rotor, so distributor to spark plugs is solid, its not that.. That means its either a fuel issue, or an air issue I suppose.. Im thinking swapping injectors next, but idk. I think before I do that, im gonna look harder for vacuum leaks, but man i looked pretty hard before didnt see anything..

I dont think it would be injectors tho because if it was the misfiring cylinder would be the same one wouldnt it? That would mean all my injectors are just randomly not firing sometimes during idle, which seems very unlikely.. Im thinking vacuum air issue i guess. Ill look harder at my intake manifold gasket too i guess..

man this is a bitch to figure out.

If my intake gasket is leaking for one cylinder, could/would it cause a misfire on all cylinders randomly? It doesnt seem like it, but idk