The Mysterious #3 & 4 mis-fire solved - Maybe

[OB99W]

The sister's Imp threw a #4 code - it turned out that when the "old" plugs were replaced (gap was 080 - yeah, thats EIGHTY - about 2X recommended) the code went away and hasn't returned. Since 3 & 4 are connected across the same coil pack, I was surprised that it didn't show 3 AND 4, just 4.[...]

Yes, the wasted spark configuration puts the paired cylinders' secondary ignition in series. However, only a few kilovolts are "wasted" on the plug that's not on the power stroke (it's on exhaust), and a little more would be if its gap were overly wide. So it's possible that #4 required just a bit more "juice" than #3 to fire properly, and sometimes wasn't getting quite enough, while #3 still managed with the lowered spark energy available.

 

This happens more often than might be imagined. Certainly, if the gap or resistance became sufficiently excessive, both cylinders could be affected. However, sometimes one cylinder will need more spark than the other, and when it misfires the problem is noticed and gets corrected before it becomes bad enough for both to misfire.

 

Another quirk of the wasted-spark arrangement is that the "companion" plugs receive spark of opposite polarity, so sometimes the one that's negative at the center electrode fires more readily.

[subsince77]

I had a question along these lines. The NGK Laser platinums are supposed to be gapped at .044 out of the box. It says on the box not to adjust the gap because you can damage the plug. When I first started using them, I checked quite a few, and they were always right on. So, I always just put them in right out of the box now. Is that a bad idea?

[frag]

I had a question along these lines. The NGK Laser platinums are supposed to be gapped at .044 out of the box. It says on the box not to adjust the gap because you can damage the plug. When I first started using them, I checked quite a few, and they were always right on. So, I always just put them in right out of the box now. Is that a bad idea?

 

Why would it be? I do the exact same thing.

[DrRock]

Hi all,

 

I, too, am getting the cylinder #3 and #4 misfire codes. I have no solution, but perhaps if I describe my symptoms it may be useful.

 

Facts:

1998 Outback manual transmission

miles: 149,000, CCR engine installed at 124,000

new coil, new wires, new plugs have not solved the problem.

 

 

I started getting this code shortly after the CCR engine was installed, never had it on my original engine. I get the CEL only if I go over 70 mph (freeway) and the temperature is less than 50 degrees F. Warmer weather and slower driving don't cause the CEL to go on. For some reason the combination of high speed (or just high RPMs) for a prolonged time during colder weather cause the problem.

 

Ideas?

 

thanks!

 

Kevin

[subsince77]

Hi all,

 

I, too, am getting the cylinder #3 and #4 misfire codes. I have no solution, but perhaps if I describe my symptoms it may be useful.

 

Facts:

1998 Outback manual transmission

miles: 149,000, CCR engine installed at 124,000

new coil, new wires, new plugs have not solved the problem.

 

 

I started getting this code shortly after the CCR engine was installed, never had it on my original engine. I get the CEL only if I go over 70 mph (freeway) and the temperature is less than 50 degrees F. Warmer weather and slower driving don't cause the CEL to go on. For some reason the combination of high speed (or just high RPMs) for a prolonged time during colder weather cause the problem.

 

Ideas?

 

thanks!

 

Kevin

This seems to be a very common but elusive problem. I think all of the solutions that you find in this thread and others like it may, or may not, solve your problem. Nice huh?

 

My latest is to focus on the fuel avenue. I began to wonder if I have a slightly, or somehow intermittently plugged injector. I have run two bottles of BG 44K through with a little break in between bottles. It has been about 3 weeks since my last CEL. most of that was around home driving, but yesterday I spent 3 hours on the highway with no CEL. All I can do is keep trying things. Again, at least this is only an annoyance, and never seems to actually casue a real problem.

 

I also bought a used ECU, but I have not installed it. I have been too busy, and with no CEL there has been no reason.

 

As for the CCR engine, typically you keep your old ignition and injection parts, so I don't know if it would be the fault of the new engine.

 

Oh, one last thing, I met a guy that had this problem for a while on a 97 OBW. He discovered that unless he grabbed the plug wire with a set of pliers and pushed it hard into the coil, the wires did not fully engage the coil. I'm not sure if that was a male or female coil. I have no such problem on mine, but you might want to check it. I think the thing is just way to sensitive to "misfires".

[Scoobydoo]

I'll chime in that replacing the neutral switch seems to have resolved misfire codes that have been going on for years and recently more serious stumbling and loss of power. We even replaced the engine (for head gasket reasons) and the misfires were still happening. That was frustrating.

Thanks to the USMB community for saving me a pile of money at the mechanic (and I bet he would never have solved it either. He's not going to spend hours reading USMB just to fix my car). Donation made.

 

Car is 98 Outback with 340,000km.