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Bad igintion coil

Howdy, found out today that my third ignition coil is bad, it’s a Honda civic 03’ my question is, do I have to buy a new ignition coil. I had a clerk tell me I could switch the coils and it would run fine? Is this right? could I just switch the ignition coil with another ignition coil? This doesn’t sound right. Well If I do buy new one which would be the third ignition coil? is it counted from left to right or right to left? Are there any telltale signs of a bad ignition coil on sight?


Switching ignition coil positions would just transfer the problem to different cylinders. Don’t know why the clerk would think this would solve anything.

Switching the coils is only a way to verify that misfires on a particular cylinder are caused by the coil. If the misfires follow the coil, the coil’s bad; if they don’t, the problem is elsewhere. It fixes nothing.

Methiinks the clerk made a misstatement. It’s unfair to criticize him, since he’s probably a high school student in the daytime with limited automotive knowledge. Or he could be an unemployed software engineer just trying to pay the bills. Or perhaps he has a liberal arts degree…

Sorry about that last one, I couldn’t resist. It’s complicated.

Most auto parts clerks have no idea about mechanical things. Burger flippers at McDee’s have no idea about raising cattle…even though they work with the product. I agree with both other comments…switching the coil would not improve the running of the engine one whit.

Where are you buying these coils? Is it always the same coil? I would buy it Napa or Honda. If it is the same cylinder I would change the plugs.

Yeah, what M-Bike said. (Not a about the liberal arts thing!) As a first step in trouble-shooting the problem, swapping coils is a good way to diagnose if the coil or perhaps the spark-plug is at fault. I’ve done it to be sure that was indeed the issue.

Do you mean the third coil you’ve had to replace or the #3 coil? A common reason for coils to fail is that they are trying to fire a worn out spark plug. Or the plug boot has gone bad. And sometimes parts just fail. At any rate just moving the coil to a different cylinder won’t fix the problem, it will just move it around.

I would replace the coil and all 4 spark plugs. If another coil goes bad soon then I would replace the remaining 3.

@"the same mountainbike"‌ Or perhaps he has a liberal arts degree… Automotive knowledge and liberal arts aren’t necessarily mutually exclusive, though they are an odd combo. I consider myself a fairly competent mechanic, and I also earned a B.A. in Philosophy from a small liberal arts college.

Alrighty, I think that’s actually what he meant by switching the coil. I can determine if in fact it’s the ignition coil or the spark plug. If after its switched out to a different slot and re-read and comes back as a new slot than I know it’s the coil but if it’s on slot#3 again than I know it’s the spark plug. It could only be those two things, correct??

@asemaster The code reader stated a bad ignition coil at the 3rd slot, not sure if that’s from the left to right or right to left, I’ll guess the former.

A little while before the check engine light came on (maybe a few days) it was hesitating on acceleration up hills and at speeds ≥60 not sure if that’s more an indication of a coil or a spark plug.


It could be either a plug or coil. Replace the plugs with OEM plugs and move the coil. Then drive it and see if the bad coil moves to the new spot with the code reader.

Inline engine cylinders are numbered from front (where the belt(s) are) to back (where the transmission is).

Ok, so right to left. Thanks insightful. Here’s a pic for reference. Can’t afford any accidents.

Exactly what code are you being given?

Am I the only one willing to entertain the possibility that the problem may not be the plug OR the coil?

Misfires could also be caused by low/no compression, bad injector, etc.

And I’ve seen these scenarios

@db4690 wouldn’t that appear on a code reader instead of coils?

I’m not discounting anything but I’m still curious about what code or diagnosis led to a finger being pointed at the coil or spark plug on that cylinder.

There’s no code for a tight valve… :frowning:


I’m afraid I don’t understand your question

As far as code readers go, that’s really all they are. they list the code. And the guy using the tool has to take it from there. Meaning he has to diagnose the actual problem

The actual fault code is only a small part of the diagnostic process

In my opinion, far too many people getting codes read for free believe the fault code actually tells them what to replace

Not so simple

Ahh, the old discussion about fault codes being the diagnosis of the problem. Remember, before 1996 we had to diagnose and repair cars without fault codes to tell us anything about misfires, and often we had to diagnose and repair poor running cars with no data from the car.

In a nutshell @JimFrost‌ , a code P0303 tells you nothing more than cylinder #3 is not firing properly. It could be caused by a coil, a spark plug, a coil boot, a fuel injector, an internal mechanical problem, a mouse chewing through a wire, a faulty engine computer, a loose vacuum hose, a coolant leak, and I’m sure 20 other things. The guys at Autozone are just giving you the most likely cause, probably from a database containing info gleaned from those of us who actually understand and repair cars and do specific testing before replacing parts.

Now if you had a fault code P0353, that would indicate that the engine computer had detected a fault with the primary ignition circuit and would lead you to suspect that the coil was faulty.

An actual scan tool with full live data capability and interactive controls would give a seasoned technician the ability to have the problem 90% nailed down before even opening the hood. On most late model cars, I know whether the problem is ignition, fuel, or mechanical just by looking at all the data the car has to offer. The code readers they use at the parts store? I wouldn’t waste $50 on them.

The problem for the DIY’er is that it’s often easier and more cost-effective to pull a fault code and replace part the store suggests.