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I drive a 2001 Honda Civic EX Auto. It currently has close to 59000 miles, and it has undergone all scheduled maintenance/oil changes. Basically, the car has been taken care of, very well. Anyway, the other day, after exiting the highway, my Check Engine Light came on. The next day I went to my mechanic. This guy is a certified Honda Tech. He works at a local dealership throughout the day, and he owns his own garage, where he works at night. He services all sorts of cars, and he knows what he is doing. We ran the code reader, and it came up with "Misfire on cylinder 4." I'm going to leave the car, overnight, tomorrow or the day after, so he can run some more detailed diagnostics. Anyone have this problem?

 
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spark plugs ever been changed?

 
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Nope, they have not..

 
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How much are spark plugs, btw? Is it normal for them to go at this mileage?

 
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maybe. they are platinum rated to 100k but no way would they last that long in real life. it could be the plugs. and if you don't feellike paying alot just get some copper ngk vpower for $8 a pack. plugs are the first thing i'd try. i was getting a misfire cause of blown headgasket and coolant leaking into the plug.

 
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Exactly how much did that cost to fix?

 
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i would start by checking to see if the plug is fouled and if the #4 wire is good by starting the car and using a spray bottle and spray water on to the wire, if it sparks then you have a bad wire. if none of that helps and the car is running smooth reset the code and drive it for a while and see if the problem persists.

 
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When the light come up this mean you have several times misfire. Have you ever used fuel treatment?
First to check: spark plugs as mentioned above. Check the spark plug on cylinder 4. Put also some fuel treatmen in the next gas tank to help to clean the injectors.

 
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mm injectors.. I'm not sure if this is realted. Unfortunately, about 14 months ago, someone had put sugar in my gas tank. (Yes, broken into my car, opened the fuel tank, and filled me up with sugar.) Anyway, after that, they replaced the fuel pump, tank, and injection system. The same injectors you're talking about? If so, they should be new?

 
Rep Power: 813

i paid $500 for them to swap the head gasket. but i think yours is something else. a misfire usually means the spark plug is not firing as well as it should be due to various conditions. the plug wires, coils, plu itself, or any kind of problem associated with the electrical system. ofcourse if the injector isn't supplying fuel, there is another problem. try and swap the injector to a different cylinder later and see if the problem switches to the new cylinder. or just get an injector. alot of people sell stuff here for cheap..

 
Rep Power: 454

whenever you have a misfire on only one cylinder, the normal thing to do is since our cars our COP (coil on plug, no wires for whoever suggested checking the wires), swap a coil from the number 3 cylinder with the 4 cylinder and put the coil from 4 on 3. then start and run the car and when the misfire code comes back, check and see if it is on the same cylinder. If it is still on cylinder 4, then you know the coil was good. If it went to cylinder 3, then the coil was faulty. DO the same with the injector, move it around, same with the spark plug. If all 3 prove fine, if the car is running like ****, do a compression test on cylinder 4.

 
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While streetglower is right, I'd start with a new set of plugs first. 59k is enough for the first set.

 
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Alright, everyone, my mechanic went ahead and chaned all 4 spark plugs. (The car has 60k miles, so it was a good idea, nonetheless.) Also, he did a compression test, and everything checked out OK. However, after some driving, the CEL is back!! Hmm, he had also swapped the coil pack, I believe. I will go back to him and see if the misfire changed to a different cylinder. If it did, then, that is the problem. Now are coilpacks usually switched, all four at one time? How much are they?

Thanks.

 
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Not sure on the cost, but you only need to replace a bad coilpack, not all. But the CEL code will tell more.

 
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Hmm, well, besides the coilpack? Could anything else be the problem? The spark plugs were changed, and the compression tested OK. (The fuel injectors were changed last year.)

 
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If the compression was ok, spark plugs were replaced, are you positive he swapped ignition coils from a different cylinder? May want to check and see, or otherwise have the code scanned again and see if the misfire moved cylinders. Its possible that he did move the coils around and now the misfire is on another cylinder indicating a bad coil.

Also just cause the injectors were replaced a year earlier doesnt mean one wont be bad. Have those checked too.

 
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Alright, here is an update. We had switched the coil to another cylinder and waited to see if the CEL came back on. It surely did, but I still have a misfire on cylinder 4! So, basically, the spark plugs have been changed, the coils are fine, and the compression tested to be good. My mechanic, who owns an after-hours shop, will take my car to his Honda dealership, tomorrow morning. He will run detailed diagnostics and let me know what's wrong. Any other ideas?

 
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next thing I would do would be to check the injector. Check to make sure it isnt sticking open or stuck closed.

 
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then do a coolant system pressure test just in case...

 
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The plot thickens.... process of elimination. I'd agree on the injector, and coolant pressure test next. MAYBE even a valve that's a little tight.

 
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Well, here'a another update. My mechanic checked the injector on cylinder 4, and it was clogged with a sand/sugar substance! Ok, in October of 2004, my car was badly vandalized, and the gas tank was filled with a LARGE amount of sugar. The insurance covered it, but the injectors and fuel pump were changed, along with the fuel tank being cleaned. Since then, the car has been garage kept, I have purchased a locking gas cap, and a very nice alarm system. To make a long story short, there is no way someone has put sugar in my tank, again. However, the mechanic suggested that, possibly, the previous cleaning was not enough, and there was residue still present in the tank, and over the last 14 months, that residue has worked itself back into the injectors. Could this be possible?

 
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Yes.

 
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I'm guessing that maybe a tiny bit of residue was left remaining within the fuel components, and they have basically deposited on the injectors within time. However, if the injectors are cloggged, the fuel pump must be, as well. My mechanic suggested replacing the injectors and fuel pump. I will speak with the dealershop, tomorrow, and I will ask them if they will warrant their previous work.

 
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Well, my mechanic gets a good price on oem parts, since he works at a dealership, as well. He quoted me 550, for parts (fuel pump and 4 injectors) and labor. What do you think? (He also took apart the other injectors and said that they were some-what clogged, as well.) Now, after all this, will the problem finally be solved? I mean, I dont want to annually replace a fuel pump and injectors..

 
Rep Power: 454

As with replacing the injectors and pump, you need to have the fuel system throughly cleaned out. putting in a new fuel pump and injectors will temporaily fix the problem, but if there is still residue in the tank and lines, it will eventually make its way back to the injectors and clog them again.

I would take it back to the dealer who first did the cleaning and make them redue it.

 
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Ok, I just found out that the entire fuel tank was replaced, along with the fuel lines, the fuel pump, the injectors, and even the O2 sensors. How could the injectors still be clogged? There can't be much sugar in the injectors, because the car is running smooth. (Last time, when I actually had sugar in the tank, it would barely accelerate, and it kept on dying at traffic lights. Also, I have already gone through 2 tanks of gas, since the CEL light. If there was a larage amount of sugar put in the tank, the fuel pump would have already given up; the car would be undriveable.) Could they possibly have missed something, even a tiny amount?

 
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my guess would be that you had sugar crystalize in the fuel rail. if they replaced all of that stuff and didnt clean out the rail, there may have been some in there. Not too sure.

 
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Unless you properly flush or replace EVERY part, they could have missed something. But don't rule out your gasoline. If you get bottom gas from your favorite station, you can get similar residues. I'm not sure I'd replace the fuel pump, though. It flows a MUCH larger volume, through much bigger lines. The chances of it getting gunked at this point are virtually nill. MAYBE the intake filter, but I doubt the pump. The injectors are much, much finer, and even small residue could accumulate there. They can be cleaned, if you are on a tight budget... but replacement is a sure thing.

My guess is that not ALL the fuel components were actually replaced the first time, though.

 
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Hey man, can you explain what you meant about the fuel pump getting "gunked?" I'm not exactly following.

Thanks.

 
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i would just buy some used stock injectors from here. usually people have all four really cheap like $50. in case it happens again you didn't waste much money