Today the car we've got in the shop is an E46 M3. The problem it's having is a misfire on a cylinder or a tube. We're not sure which ones it is, but what we're going to do is show you how to identify it and determine what the problem is.
Now we're talking about a misfire that's probably electrical related, nothing that's a major issue down in the cylinders or pistons or anything like that. What we've got here is a vehicle that has a MIS, it has no engine noises. It's a smooth running car other than one or two cylinders missing. So we're going to start the car up, so you can see what that's about.
Now what we have got going on here is -- I've put a glass of water over here so you can see the movement on the water changes as we move cylinder. Now here is your 6 coils right here. One coil over each cylinder. Right below the coil is the spark plug. So what I am going to do now, while the car is idling and we got to listen carefully, I'm going to disable one coil at a time by just disconnecting it.
Now, I've already identified that number one is the issue that's why it has got a marking on it, but this is what it's like. If the coil is not reacting at all, that the coil is dead. I have disconnected the coil, you don't see any engine change. It's disconnected. I have got the wire actually off the coil. Okay? I'm going to put it back.
Now I'm going to take another coil and disconnect it, you obviously see a drop in RPM, my water glass is shaking quite a bit more over here. I am going to show you what two missing coils is like. This is actually already two missing coils, this is three. That's the M3 running on three cylinders.
Well, I know that this one is functioning. I know that this one is functioning, but I can tell that this one when I disconnected makes no difference. Now, that doesn't tell us necessarily that it's a bad coil. What it's telling us is that cylinder is dead. We've got a coil. We've got a spark plug involved. So what we're going to do now is we're going to switch these two coils. If the dead cylinder follows the coil, it's a bad coil. If the dead cylinder stays with that cylinder, we either have a bad spark plug or there are other some issues of fuel or something like that, that's failed on this car.
Now we're going to take it apart and we're going to switch these two coils. Now to remove the coils, it's helpful to have one of these removal tools, which is just an insulated set of pliers that will grab on to the coil and it's also designed to grab on the plug wires. So I'm going to disconnect the connector, pull the connector completely away from the coil. Then what I'll do is I'll grab it from the top here, that's the coil right there. We'll take the other one out.
Now, this was the good coil. I'll replace it in the spot that I am suspecting - it has got a bad coil. They do index these coils, so you want to make sure that this little notch goes into this little notch right here on the cylinder head. So I am going to put it in there. You'll feel it fit over the spark plug and then you'll push it down.
Now, we are basically just taking the two coils and moving them. Everything else is where it was before. Now we're going to start the car up again, and give it a test. Okay, we've got our coil flopped; now I am going to disconnect the connectors, one at a time.
Okay, now we have a functioning cylinder number one, because now we've got a MIS after we disconnect number one, before it was dead all the time. Now, I am going to disconnect number two, no reaction at all. So what we've got here is we know that coil number two which was originally number one is the faulty coil. So now what we're going to do -- I am just going to check one more time, make sure number three, here we have a MIS, so we've got one dead coil. It's now number two.
Now what we are going to do is turn the engine off and we're going to swap out coil number two. Here is the new coil and this one happens to be a Bosch Coil, we're going to install this, push it down to the bottom, we wanted to index on our little index mark down there, it will push down. You'll feel it kind of snap down in there, because it does have a rubber boot that slips over the spark plug, you want to make sure it snaps all the way down.
Now, what we're going to is do our connector, we've got it connected. Now we're going to start the car. Now you are going to notice that we don't have any MIS anymore, the car is really smoothed out. I am going to test it one more time. There is our MIS. We should have a MIS here also. Here it goes. That tells us now that we've got all six cylinders working.
Now what you will have to do is reset engine code lights because you've obviously had a misfire codes, possibly a catalytic converter failure. All of those lights will have to be reset because that's the result of what's happened here. So the reason these coils likely to fail is, mounting the coils right on top of the cylinders brings engine vibration into the coil and heat from the engine into the coil. On earlier vehicles where a coil was mounted remotely or off of one side on the fender, it didn't have to do with all that direct engine heat and it didn't have to deal with all that engine vibration.
You got to remember when this car is doing 7,000 RPM and you're really moving along on the track, you've got a lot of activity going on there, a lot of engine noise, a lot of engine harmonics and a lot of engine heat that's transmitting directly into that coil. So the car has been finished. All you have to do now is reset your code lights and you're ready to go.
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