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First off, I'm a noob, both to this forum as well as DIY auto maintenance. I've got a 2003 civic ex with 140,000 miles. For about a year, the cel has come on, gone off, come on, gone off, etc. Since I live in CA and needed to get my car smogged, I figured I should probably look into the problem. I bought a code reader and it read 6 codes, p0300 - p0304, with 0304 read twice (?). 2 minutes of research told me that a likely cause of these codes is bad spark plugs. I have never had mine changed, so this seemed plausible. Did that 2 days ago and the cel went off. It came back on today as I was puling away from a stop sign. When I got home, p0304 came back. 2 more minutes of research told me a second likely problem was the coil pack. I swapped out the coil pack from cylinder 4 with cylinder 1, and erased the code. If the cel comes back with code p0301, I will know I have a faulty coil pack, if p0304 comes back does that point to the plug wires? If my logic is faulty, please steer me in the right direction.

 
Rep Power: 307

Coil on plug eliminates plug wires.

See what code you get and go from there.

 
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Like I said, I'm new to this, so I probably got my terms wrong. Are you saying that the coil pack (tube that fits over the spark plug inside the spark plug cylinder) takes the place of spark plug wires? What about the wire harness that the coil plugs into? Could a malfunction exist there that would cause a cel to come on?

 
Rep Power: 811

the wire harness is usually never an issue, those are low voltage wires. all the action happens in the coil pack (which replaces the distributor and wires of older cars). and ofcourse there are four coil packs one for each plug. its way more efficient technology.

 
Rep Power: 312

If you had coil pack issues you'd know believe me. The car would jerk and throw you around and it wouldn't be driveable. They are designed to last the life of the car and never really need to be replaced unless defective or they have premature failure. But again, you'd know if a coil pack was shot. The coil pack (and a few sensors) replace the plug wires and distributor under the hood. You do however need to figure out where the code is coming from, you didn't by chance use bosch spark plugs did you?

Figures gearbox beat me to it!!!

 
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I did use Bosch. Tell me more.

 
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They just dont fair well on a Honda.. Replace them with NGK or Denso

 
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Get some oem plugs.

 
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Could using a Bosch plug cause the cel to come back on that quickly? I have no problem replacing them if I need to (lesson learned). I just want to make sure I am not overlooking something else. Thanks for all the replies, btw.

 
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yes i have heard of new bosch plugs causing misfires before in hondas

 
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It happens all the time. As was already said, Bosch+Honda=Not best friends..... NGK+Honda=Bff's

 
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Crazy. I'll give it a shot. Thanks. Before I tackle next week's project, is there a brand of brake pads I should buy?

 
Rep Power: 811

stick with the honda pads

 
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Changed out the Bosch plugs with NGK platinum plugs. I was surprised how discolored the threads were on the old plugs. They look similar to the original plugs I took out only last week. Is this discoloration normal? I read the cel codes just before pulling these plugs and it read 5 (p0300-p0304). I have cleared the codes, so I guess I can only wait to see if they come back.

 
Rep Power: 811

plugs are supposed to be light brown mostly and maybe some black around the threads and base.

 
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I switched to the NGK plugs and the cel went off....for about a week. I heard that corrosion on the battery terminals could cause the problem, which I had. Cleaned off the terminals and the light went off (prob because I disconnected the battery in the process, no?) but it stayed off for two weeks this time. Light came back on today, pulled the codes: p0300, p0304, p0303. This time, the car is not sluggish at all. The only symptom I am noticing, and I don't know if it is related at all, is that there is a strong exhaust odor at idle. I had not noticed it before, but that doesn't mean it wasn't there. Any ideas? Thanks in advance. Rob.

 
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Light went off today. What could cause the code to come and go intermittently?

 
Rep Power: 811

check to be sure the factory ground wires are tight and not corroded.

 
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After changing both upstream and downstream O2 sensors, the CEL has been off for over a week. However, a new symptom has emerged. After cold starts, there seems to be a delayed throttle response in first and second gear. During the delay, I can mash the accelerator and there is no response. If I were not to depress the clutch, the car would most certainly stall out. After the delay passes, the car runs fine. still no CEL, and the ECU is showing no code. Is this a different issue altogether or a symptom of the same problem? I would appreciate any thoughts. Thanks. Rob.

 
Rep Power: 252

What type of O2 sensord did you use?

 
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Denso. Exact fit oem.

 
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Any problems with the heater? Consistent?

I recently had all those exact codes...air in the coolant system caused by a bad head gasket. Codes haven't been back on since the repair. I read somewhere the air gap can cause the misfire codes via the temp sensor.

 
Rep Power: 252

The NGK plugs you used should be

NGK: PZFR6F-11

If you want to use Denso the number is

DENSO: PKJ20CR-M11

This is what the book calls for, anything else may cause misfires.

Gap is 0.039 to 0.043 however you really shouldnt gap irridiums hence why buying them from the dealer is a very good idea.

Check for vacuum leaks

Cleaning your throttle body and IAC would be a good idea. (Probably will help the problem but not solve it)

 
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The misfires you had earlier meant that cylinder was running rich. Might have clogged the catalytic converter. That would explain the sluggishness.

 
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When you had this issue did you also have intermittent heat?

 
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Yes, I also had intermittent heat.

 
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hey guys,

2003 civic need to do a tune up ,
will be required ? if possible any links to product ..
so i can search them up and order them online as the mechanic are a rip off.


thanks H crew

 
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How many miles do you have? When was the last 'tune up'?

 
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......and has the timing belt been replaced ???

 
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@ theshushiboy -

it has 277202 km = e - test was recently done. and i just purchased the car.

@ CraigW - not sure as its a recent purchase and havent had time to visit the mechanic ,