Weird: Double the rate of ignition on one side of engine
 

This one has me stumped; I did a service the other day, usual fluids/filters/plugs. Anyway I washed the engine a few days before and some water got under the lead boot (Cyl#3) and into the spark plug recess (SOHC) so the car was misfiring as the spark was taking the easy way around it.

Anyway while doing the service I got rid of the water around the plug and replaced the sparkplugs with new ones. I got the timing light out as the car was misfiring every now and then and I wanted to see which cylinder it was. To my surprise I noticed that the left side of the engine (facing the engine bay) so cylinder #1 and #3 were firing at twice the rate of cylinders #2 and #4. The misses were on the faster cyls. Now the weird thing is that #1 and #3 are on different coils so I'd expect all cylinders to be firing of like crazy. Here’s the electrics schem...

[URL=http://www.uploadit.org][IMG]http://server2.uploadit.org/files/loccomoffo-coils.jpg[/IMG][/URL]

[I]The numbers next to the ECU, ignition module and coils are the connector numbers.[/I]


I tried separating the leads to make sure the timing light wasn't picking up a magnetic field from the other lead or coil. I dismounted the coil pack and rested it on wood to make sure it wasn't shorting through the intake manifold.

I tested the primary coil's resistance 0.9Ω (both) and the secondary coils resistance 13kΩ (both) and now I'm stumped! If each coil is discharging at double the rate only on their left side why aren't the other sides of the coils following suit seing they are on one coil?? The right hand side is firing normally like it can't see what the left hand side is getting up to.

Anyone see this before? Or have any ideas as to what to test next? :D56CC97E5391454A915


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Please explain "firing at twice the rate "?
How did you determine this?

BTW, this is a wasted spark set up.

When I use the timing strobe light on each of the leads, I can see from the strobe that the left hand cylinder's leads are generating a spark twice as often as the right hand side's leads.

I understand that this is a wasted spark system, that is why i find it weird that a single coil produces a spark at one rate on the left hand side and a spark at a different rate on the right hand side (both "sparks" originating from the same coil)

I had a think about this and I think the spark might be shorting between the two left hand side leads (timing is 180deg out between these leads so makes sence). As for the diff rates across the same coil: The spark/voltage peak is probaly filtered through the coil as it's basically a large filter/choke. So the residual peak voltage on the right hand side leads isn't high enough to register with the timing light....? Just thinking out loud :)

Anyway I'll swap the leads around tomorrow to see what happens. A friend made me an inductive lead pickup from an old timing light for an oscilliscope today, might give that a whirl as well.

OK, I swapped the leads around today from left to the right and vise versa and it hasn't changed anything. The left hand side is still firing twice as often.

Hooking the induction lead pickup and the primary coil signals to the osciliscope didn't give much insight either :( Although the signal from the ignition module had a huge voltage spike at the begining of the signal to the primary coil, is this normal or is the signal wave form supposed to be quiet flat, ie no huge spikes?

It's all pointing to the coil now, might be an internal short closer to the left hand side. Will have to swap it out and see.

Are all original Subi coils created equal? Or coils form particular models outperform others?

So today I swapped the timing belt on my car with a friend of mine. I told him about the weird rate of fire from the coil and so we tested his 2000 WRX to see how that looks, turns out his coil is behaving just as weird!! So I did some searching on line and have come across this:

[I]"One other problem that we have found quite often is an injector failure that leads you to make numerous attempts at resolving an ignition problem, only to find that the spark was going to the wrong cylinder because there was no fuel to ignite in the correct one. Remember that the spark is going to take the easiest route to ground and that might turn out to be the opposing cylinder ... The inductive spark tester comes in handy when it shows no spark activity to a cylinder with a good plug, wire and compression, but the same coil is sending plenty of spark [COLOR="red"][B][COLOR="Red"][B]twice as often[/B][/COLOR] to the cylinder that’s directly opposite[/B][/COLOR]."[/I]

Full write up here:
[url]http://www.babcox.com/editorial/ic/ic30332.htm[/url]

Very interesting!! It looks like the injectors will need a looking into now.

Anyone else try to see how their coil fires to each cylinder?