My engine is misfiring?

Would not hurt to run a scan and look at all tune items. It sounds like you need to replace the spark plug which is easy but I would do a full tuner up here are two guides to help us.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

and

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

Please run down these guides and report back.

Engine Performance problem
2005 Honda Civic Automatic
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I recently purchased a 05 Honda Civic EX 2door and I didn't know it at the time, but I soon found out that the engine has some sort of problem. First, I thought it was just something about changing the car oil and changing the oil frame, but soon after I did those 2 things to my car it still didn't work. The problem is the engine is misfiring. I took it to Napa Auto Parts and they put the check light engine tool in to figure out what was wrong and it come out with random misfires. I've tried a couple of things to it, but it still didn't work. I'm wondering if you guys can help me figure out what is wrong? Do I need a new alternator because I think that the alternator isn't putting enough power into it, so it's causing the random misfires. PLEASE HELP...

Get the alternator load tested and follow up with P0300 code could be vacuum leak or bad gas.

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel

As soon as I start up my car heavy white smoke comes out. when I continue to drive it still comes out. there was oil in my intake and throttle body so I do not know where the oil is coming from. I changed out my spark plugs and it is still. had no compression on one of the cylinders and the car just smokes when it is idling. it does not smell normal or too good. I checked the head gasket but I did find this.

In the picture below you can seal the spark plug valve seal is ruined.

Heavy white smoke and no compression sounds like a failed head gasket letting coolant into the engine. Only real options are to pull the head and either replace or rebuild it. If the body is in good shape and you like the car you might want to just drop a used engine into it. If you have the tools you could tear it down and see what is the problem. Then decide if you want to rebuild/replace depending on the damage.

My car is misfiring on all cylinders checked the usual plugs and coil packs (Civic type r ep3) my next thought was injectors. I happened to disconnect my IAT sensor and the misfire stopped, I have ordered a new one as it is only £30 but I am thinking it is not the part that is faulty and the misfire is going away due to the extra fuel the engine management is putting in with the IAT disconnected.

if the code is 0300 then it is a random misfire and may be low fuel pressure so check that as well as a vacuum leak like a broken hose/cracked/off etc. See link for fuel pressure.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

With the IAT sensor disconnected

IAT connected

do a compression check and get back with results as well as fuel pressure like I asked the first time.

Good Afternoon! I have a 2002 Honda Civic EX that is running horrible. My problem started on my way to work 1 morning when I attempted to pass a slow driver. As I pulled into the passing lane my car begain to surge and hesitate as though I was losing fuel. I took it to a buddy at a auto shop and we hooked the car up to their computer. The computer read that the catylast system failed and that there was a miss fire in every cylinder. I place new plugs in the car and put on a new converter and 02 sensors. This did not solve my problem! A mechanic there at the shop said that it could be the fuel pump and filter or the EGR valve. I replaced the fuel pump and filter and nothing chenged. I was just wanting a second opinion on the EGR valve before I buy the part and that not work. Do you have any ideas?

Hi davidsellers,

After the repairs and replacement of parts, did the Check Engine Light still show and what are the trouble codes present?

Did you erase the trouble codes after repairs?

Yes, I cleared the codes, but they came right back on once I begain to accelerate out of the parking lot. The code that it is pulling is a missfire in 1,3,4 and a multiple cylinder code P0300.

Shakes or Wobbles problem
2002 Honda Civic 4 cyl Manual 179,00 miles

Hello, I have problem with my 2002 honda civic dx coupe. It is misfiring and i only have been feeling it when it is at idlle. It shakes moderately and it does this whenever im idling and it has also begun to do it when I start the car in the morning or anytime during the day. The other thing is, my check engine light has not come on once while it does this, therefore it does not give me code of any sort. All of my spark plugs are fine, and I really don't know what else to do. Please advise, Thank you!

Check for vacuum leak.

There is not a vaccum leak. The hoses from the rear to the front are good and i have checked the evaporation system and used a spray on the throttle to check for any leaks and have not found any.

Sometimes, if the misfiring is not bad enough it won't set off the computer. Even if the plugs are good, if they are more than a year old, I would still start with that. I doesn't cost too much (less than $10) to replace the plugs.

I just replaced them two days ago. Seemed to be better the first day and now it is back to moderately misfiring again.

Next thing to check is sensors. Try cleaning your idle air control valve and EGR valve. Usually if you have too much carbon deposit in the system, you will feel as if it is misfiring.

And being a Honda, I would also check your coolant temp sensor.

Shakes or Wobbles problem
2002 Honda Civic 4 cyl Manual 179,00 miles

Hello, I have problem with my 2002 honda civic dx coupe. It is misfiring and i only have been feeling it when it is at idlle. It shakes constantly whenever im idling and it has also begun to do it when I start the car in the morning or anytime during the day. The other thing is, my check engine light has not come on once while it does this, therefore it does not give me code of any sort. All of my spark plugs are fine,There is not a vaccum leak, and The hoses from the rear to the front are good and i have checked the evaporation system and used a spray on the throttle to check for any leaks and have not found any. and I really don't know what else to do. Please advise, Thank you!

I assume you are trying to solve this yourself?

If so, do a cylinder balance test when the car is mis-firing. Unplug the injector clip one by one. If the engine starts to bog down and stumble or even stall, that is a good sign and tells you that, that particular cylinder is firing properly. If you unplug a injector clip and the engine note does not change you now know which cylinder is acting up and you can go on to coil tests (since that vehicle is ICP), injector tests, compression, etc.

Let me know what you find.