RB20DET Running on 5 cylinders when raining or damp?

[trickey1991]

Hey Guys,

I have a R32 skyline and its running good when the weather is nice, but for some reason whenever it rains or gets damp outside the car periodically runs on 5 cylinders(sounds like a subaru) it's very weird.

Any help or ideas would help:

I'm thinking maybe a bad coil pack, but how do I test them?

[fliprayzin240sx]

Did you make sure you're not getting water into where the coilpacks are at?

[FlatBlackIan]

Most likely a bad coil. Pull them and check for hairline fractures on the hard plastic portions. It could also be a wiring issue for that specific coil, or even a ignitor that is loosing one of its channels.

[trickey1991]

Did you make sure you're not getting water into where the coilpacks are at?

I dont think water could get to them, as I have a hood.. But I dunno no

Most likely a bad coil. Pull them and check for hairline fractures on the hard plastic portions. It could also be a wiring issue for that specific coil, or even a ignitor that is loosing one of its channels.

I just seems weird because it happens when wet or damp

[FlatBlackIan]

I dont think water could get to them, as I have a hood.. But I dunno no



I just seems weird because it happens when wet or damp

Its not wierd at all, its physics.

Electricity has a very hard time moving through air, but even a small amount of moisture in the air makes it much easier. When it is raining, there is A LOT of moisture in the air.

It takes a certain amount of energy for spark to flow through the base of the coil, and the spark plug. This is called resistance. The spark will make the jump from the spark plug electrode to its ground strap because that is the path of least resistance. If the spark has an option other then going through the spark plug that offers less resistance, it will take that path.

Under dry circumstances the hairline cracks in the coil pose no issue as there is still more resistance to jump out of the coil then go through the plug. When the resistance in the air changes due to additional moisture, that resistance ratio changes. If the resistance in the atmosphere drops enough, spark will change paths and you lose a cylinder.

Pull all your coils and inspect them for cracks and carbon tracking. Carbon tracking is a sign of spark leak.

Its a very common problem with coil on plug ignition systems. I have replaced hundreds of coil packs on engines from every manufacturer.

If none of the coils show damage, start checking for open wiring, or a failing ignitor.

[trickey1991]

ok!

So I replaced one coil pack 2 weeks ago because when we pulled the plug off it and then plugged it back in it ran on 6 cylinders. It was fine for a week then decided to run on 5 again for about 10 minutes.

Tonight I started the car and it ran on 5 for about 10 minutes then was on 6 the rest of the night.

I don't know what is going on.anyway to really 100% determine?

It's really bothering me

[BoostWanted]

Bad injector by any chance?

[trickey1991]

still doing, this hoping its an igniter I just bought a new one waiting for it to arrive.

[greenwood]

take your coils out and cover them in liquid electrical tape.

[PureRush]

Most likely shirting somewhere if it's not the coil packs

[codunc]

the ignition harness on these motors is prone to damage from heat. its worth checking out as they can get brittle and short out

[trickey1991]

OK SO!

did an OHM test on all the coilpacks, they all were 1.3OHM except for 1 it was 0. I replaced it, and put the 0OHM one just on the harness clip with a spare spark plug and started the car , it still sparked and everything so I don't think an OHM test determines whether or not a coilpack is junk.

I put the new one in, it started up on 6 cylinders and drove for like 1-2miles then ran on 5 cylinders again.

I don't know what it could be next, my buddy has yellow jackets hes letting me test them tomorrow.

any other ideas?

[Drifting Kalamari]

When it's dry out, start car, pop the hood, get a spray bottle of water and start spraying around. You may see sparks jumping across some wires, this works well for spark plug wires at least! (since you said it happens mainly when damp out)

[trickey1991]

So We tested the coil pack harness and 1 of the harness going to 3rd injector was reading 0 for signal, so we swapped it its reading perfect like the rest of the harness' but its still running on 5 cyl. I'm going to swap the coil pack tomorrow and also that plug since it could be fowled since I drove last week 160miles on 5 cylinders.

[trickey1991]

so i swapped the coil pack out of 3rd cylinder today(the one that was not getting signal) so I changed the coil pack and re gapped the spark plug and took it for a drive and it still is running on 5 cylinders once it gets warm. first 5minutes is fine. from 0-140 degrees(water temp) then its like a switch goes off and bang 5 cylinders... i dunno anymore.