sk88erguy

So, i read through the FAQ on POS and i understand how the POS grounds the coils which creates the spark.

But when i have tested my 5 coils with 5 spark plugs, no coil tester. The #1 spark has been weak. through all the other testing i kind of lost track of this because it was like the first day and i just forgot about it. I have checked it a few times and it is always weak.

So, i will try flipping the 2 white connectors and seeing if the weak spark moves. But if it doesn't, how could the ECU, or the wire from the ECU to the POS cause a weak spark, if it is just grounding the coils it either works or it doesn't yes?

Also, are the white plugs hot when the car is on, or the ignition? i could test them for 12v with the DMM im guessing.

UrS4boy

the weak(est) link. Just observing the spark at a plug might be a rough indication but it could also include the effect of the spark plug boot OR the plug itself.

As for the power to the coils, the harness connectors are powered by Position 15 on the understeering wheel power/relay bar. 15 is switched power, powered only when the key is in the start or run position. So yes, you could have the key on and test the voltage. Each of the two three pin power plugs on the firewall connector bar (where the white coil power connectors plug into) have three wires so it doesn't matter which white plug goes to which power plug (one of the white plugs obviously has only two wires in it). So, yes, you could swap the plugs and see if anything changes. (See diagram in the link below)

I really think your No.1 coil is weak or just not working sometimes (hence the wet plug, etc). You *might* want to examine the coil wiring for breaks or cracks in the insulation or the wire itself.

Persevere. You will find the problem.

(Can you swap coil packs with Kelly for a short time (a day?))<ul><li><a href="https://forums.audiworld.com/s4s6/msgs/206801.phtml">Click Here</a></li></ul>

sk88erguy

plug. So ill test the power supply.

We will see where it goes, but just the fact that i can tell the spark IS weak on #1 with just 5 plugs at least tells me its electrical.

Thanks for the info, I was disapointed when the shop didn't find anything and said I'm giving up, but i still have some things to look at. When it does get fixed ill be ecstatic. Crossing my fingers.

quattro5.v.2

it could let some current flow, but not be fully flipping the POS transistors 'on' so you could get a less-than-optimal spark.

if you have weak spark but swapped a known good coil pack with no result then I'd be looking back in the POS area.

given that there's a spare POS channel available with just a few quick pin swaps it's really a no-brainer to do that ASAP and report back.

UrS4boy

If the ECU signal is weak, a new unused POS channel might not perform any differently.

Here is an X-ray photo of a POS:

<img src="http://www.urq20v.com/My_other_cars/S6/POS/POS_x-ray.jpg">

Here is a photo of a POS that has been opened up, showing the transistors and the very fine wires that make the connections to the pins and which sometimes crack = intermittent poor connection/poor current flow:

<img src="http://www.urq20v.com/My_other_cars/S6/POS/POS_FA_2.jpg">

sk88erguy

Ya im using the spare POS channel now anyway, same spark.

Sloooo4esT

does kelly have good pos's you can run?

sk88erguy

at low RPM? i mean maybe when i ran his coils the plug was wet from b4, and the idle issue i still had is something different? god idk. Everything i have seen on bad coils says they get worse fast and fail at high RPM, mine has been the same problem for 3000+ miles now, if it was a coil wouldnt it get worse?

UrS4boy

Can you borrow an ECU to test the spark with a different ECU (to eliminate yours as the problem)?

UrS4boy

Coils typically fail to deliver at higher RPM (and boost levels) whereas POSs fail noticeably at low