Looking at that chart I can count 6 blue spikes where there should not be (albeit small ones) while there are no abberant red apikes. Does that indicate spark plug voltage when there shouldn't be? Like a short in the wiring?

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I have ZERO knowledge on reading Oscilloscope waveform so I do not even know what to look for.

I honestly dont know. Would need to do the same test with my 03 to know what it should look like on a good running car.

It does seem like it could all be a wiring issue or DME issue but, the DME tested good per ecu dr and it wiring wouldn't explain some of the other issues like the oil light coming on or hard downshifting, but of which can be caused by vacuum/pressure.

At this point I think I am going to just have it transported out to KC and have KC Rennsport have at it cause I am running out of ideas.

I could do another AOS but that damn lower accordion hose is just such a pain to get back on right.

If anyone has any other suggestions on what to try or parts to replace I am all for it. I dont mind throwing parts at the problem depending on what it is. Hell I would even replace the header with precat if I could find a used one somewhere.

I enlarged to about 300% I now see the small spikes on the blue line Channel A=Cyl 1
I know nothing about scope waveform, but Channel B be is not doing it.
But where he is hooked up shouldn't that be signal from the DME/ECU to the coil ?????
Not the plug firing????

according to the wiring diagram that is the coil wire from the dme. At the coil 1 wire goes to ground point 12 and another to 42.

I'm not all that good at wiring diagrams sometimes. What is that 42 circled in blue?

Anyone know exactly where GP 12 is in the engine compartment?

Coil wiring:
http://986forum.com/forums/uploads02...1627398292.jpg

Ground points. Where exactly on the engine is GP 12 though? I know there is a couple ground wires right by the AOS at the corner of the intake manifold, but that isn't what is shown in the diagram. Diagram has it more in the center of the engine, but the throttle body.
http://986forum.com/forums/uploads02...1627398321.jpg

I was looking at the Pico website.
There is information on using and testing with the Pico.
Also there is a waveform library that you can access.
Could be of some help.
Keep me in the loop on what you do with it and what you find.
After this long I am hooked...LOL

Automotive electrics is my weak point.
But if 12 is a ground point then my guess from looking at it is that 42 is a wiring harness connection with all positive leads.

The only thing at 12 is the main ground wire that goes over to the SAI pump. Been looking at wiring harnesses and it looks like the one I mentioned by the AOS & corner of the intake are the ground terminals for the coils and other things on bank 1. That is good & secured to the engine. So if it is a wiring issue it is going to be one of the other wires, a break (unlikely since it does fire) or a chafed wire.

Remember this from page 2, 10 days ago? Have you looked for this?

"Sorry to be late to the party on this one, but I had an almost exact situation last month with my '02S. Same misfire codes on one bank.
I ended up taking mine to my Indy shop where they discovered a bad #4 ignition coil housing on the engine wiring harness. (which looks to me like the only thing you haven't replace)
They state they use to be able to get just the individual housings, but now Porsche wants to sell the entire engine harness. Fortunately for me, they are still able to source the individual units. (And yes, changing one connector housing cleared all the misfire codes)
You may want to check this out before you completely get lost down the rabbit hole."

You're pretty far down the rabbit hole. Not being smart, just trying to help.

No worries. it would be strange that all 3 connectors have issues. Would make sense if it was just 1 but all 3? When they did the work was it just the housing the replaced or did the splice in a new connector with wires?

They replaced one housing. It cleared all the codes. Runs like a champ.

What is the coil housing we are talking about???

has to be just the plastic housing for the pins, only thing I can think of

Total disclaimer - I don't know **************** about a pico. But, if this tool is charting out voltage over time (which it appears to be) you have an issue with that the wiring somewhere between the dme and the spark plug.

Before you ship it out, I would repeat this test on your 03, or even on this car with cyl 2/5 or 3/6. My bet is that you won't see those spikes.

The spikes don't necessarily have to be voltage coming out of the ecu - there could be a break in the line that is allowing a short. Even a small insulation break - you know, **************** that tends to be exacerbated when things heat up (anyone who's has had a microswitxh issue knows what I'm talking about) - between that wire and another hot or ground could be causing the abberant voltage. Remember that the wire is just a conduit and your tool is reporting what it is detecting. Hell, there could be electrical short anywhere between the ecu and the spark plug tip. It's all conductive.

Here's what I would do - run the test on the different cylinders. If there are no abberant spikes, start working your way down the line from the ecu. First, cut the wire just after it comes out of the ecu (leave enough to splice back later) and run the test again. If the spikes are still there, it's an ecu issue. If the spikes aren't there, splice a new wire from there down to your coil pack and see what happens. If the spike returns the there's an issue with the coil pack wiring harness, coil pack, or plug. If there are no spikes then your car may be fixed and you owe me a beer. Or I just wasted a day of your time and I owe you a beer.

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Well, you can still owe me a beer, but I'll settle for doing a burbon run with you some time.

Pico is just an oscilloscope. But you do mention something that is worth thinking about. Instead of doing a pico scope I could just hook up my voltmeter.

Here is the question I have though. Coil has 3 wires going to it. ground, a voltage (not sure what voltage) and another wire. In coil ones case it is brown, black, green/black. Brown is obviously ground. But should the black wire have? voltage, ground, ?. What should the green/black wire have? The green/black wire is what comes from the dme. Dont know where the black wire really goes other then it's used by a lot of things. Injectors, all the coils, 02 sensors.

Who is our resident wiring diagram expert?

Not discounting this being a wiring issue. 2 common things with this issue for wiring. DME & bank 1 coils all use the same ground point. GP12.

The black wire goes back to vs 42, which is a connection point for power supply. My best guess is that it is the source of constantly supplied power to the coils (and radio, interestingly) and that the signal from the dme opens the circuit to allow voltage from that supply to activate the coil. So, it should be 12v steady on the black, where as the dme signal wore should be an intermittent (probably 5v) signal.

Dude, I LOVE whisky. Burboun is great, I'm more into ryes as I've gotten older though. There have been few moments in my life where I truly believed in god, and those have been (in no particular order) the birth of my children, the 3 miracles that happened on my wedding day, and the first time I ever tasted Thomas h handy rye whiskey.

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With the "PICO" you should be able to test the entire circuit on a cylinder including DME and sparkplug spark. For function, shorts, resistance, what ever.
With a two channel you could compare Cylinder 1 to another cylinder or CPS signal.
Or the cam signal. Or any other electrical signal.

The "PICO" website has tutorials on running tests on various systems.
It has a good tutorial on Coil on ignition systems including the three wire coil.
It explains function of each of the three wires.
I read the info and from it I learned that the area you have circled in blue in post #126 is (VS 42) is a constant Voltage Supply point.
The tutorial also includes known good waveforms and how to read them.

You could also go to youtube and look for "Scanner Danner" he has many videos on using an Oscilloscope.

PICO is a great diagnostic tool I wish I had one.
But the caveat is: If one doesn't know how to use it then it is of no value:eek:

After attempting to help with your issue and following everything you have tried.
It looks like most of the problem is with cylinder 1.
Although I know zero about waveforms or "PICO" it does seem that the issue with cylinder 1 is electrical.

I'm still learning pico. It's a great tool and yea, if you dont know how to use it right it's like using a hammer to put in a screw.

Yup, does feel like electrical, cause electrical could cause every one of the issues I am having and/or cause the domino effect of what is happening

Well keep me in the loop of what you do with it and the final outcome.
Always interested.:D
Sorry I wasn't able to help you resolve the issue.

You have been more then helpful, really. There are only a couple more things I think I can check on my own but those are things that I would also need spare parts of to test. Would really like to throw a new dme in, but that requires an immobilizer & key also.

If replacing the wiring weren't such a pain to do with the engine in the car I would just do that too, and still might.

Still going to get it to KC cause I want the cam actuator pads replaced and that is not something I want to do. I could do it, just dont want to.

RedTele58's post got me thinking (dangerous thing). I'm not too sure it is a connector issue, but it could still be a wiring issue, but this is where I need help understanding the wiring & coils.

When looking at the diagram the coil has 3 wires. 1 is +12v, 2 is ground. 3 goes to 42 welding point WL Motor, which I think goes to a relay if I am reading things right. The same ground is shared with coil 1-3, SAI pump motor & engine intake cooling fan motor. This ground is located right by the AOS & the outside corner of the intake manifold. Verified that it has 5 ground wires.

So, big question. If I disconnect that ground wire from the engine, should that wire still have ground connectivity? If I am reading the diagram right I dont think it should.

My question is if the gp 12 is disconnected from the motor, should there still be ground connectivity between those ground wires and ground?

I may be totally off-base on this as I have no real experience on P-cars' electornics. Having said that, most cars I've worked on, the DME or ECU, or whatever they call it, does not send voltage, it completes the ground. So, my theory is that post #1 is NOT +12v, but ground for the Primary circuit (low voltage) of the coil (when the DME grounds it), #2, GP12, is the ground for the Secondary (high voltage) circuit. The diagram shows a diode for the spark plug side, which would be the main ground, so maybe GP12 is to ground some transient voltage?? And #3, VS42, is acutally +12v. This would make sense why VS42 would hit all 3 coils and other parts.

You can test this if you have a circuit tester and connect one end to any ground and probe #3 on the harness and see if there's 12 volts. And if you have and OHM Meter, you can probe both ends of all three wires to check for continuity or excessive resistance. I'd at least check for a broken wire by testing continuity before worrying about replacing the entire harness.

Hopefully this helps get you on the right track towards troubleshooting.


EDIT: Actually, you don't need to check both ends of all the wires. If #3 is in fact +12v and you get +12v on the #3 post of each coil, then those are all good. If you have an OHM meter, you can check for continuity from #2 to any ground on the car. The only wires you need to check both ends for continuity are the #1 wires. You need to probe them at the both coil side and the DME side to check for continuity.

I think you are right. One of the pins is 12v, another is ground from the dme & the other is engine ground (gp12).

This is an area that is not my strongest. I do decent, but not great.

Here is the rub with all this though. the misfires are not constant, that are sporadic. sometimes get a lot of them, sometimes it's 30+ seconds in between misfires

I'm not great here either.

It could very well be a break in the wire with the broken ends close enough together. Somtimes it gets continuity, sometimes it doesn't. Temperature and engine vibrations would contribute to the problem. So would a short between two wires rubbing against each other in the harness. The latter is harder to diagnose because a continuity test would still show continuity. If you're lucky in that case you'd find voltage on a wire that's not supposed to have it, then that would indicate a short somewhere. Besides that, you'd have to cut the harness open and check each wire for a break in the jacket.

I've been following this thread and I empathize with you. Electrical gremlins are a PITA to solve. Hopefully at worst you just have a break in the wire and not a short.

What I found out about VS 42 is that VS=voltage supply.
It is a key on 12volt. So any VS with a number in these wiring diagrams is a key on constant Voltage Supply point.

I would think that any wire that has a break in it but still shows continuity would also show greater resistance on an ohms test.

Correct. Another way to check for breaks is by moving the wire harness while checking continuity.

Ok, well at least with all this I learned something.

So...Coil wiring is:
Pin 1 - DME
Pin 2 - Ground
Pin 3 - +12v

Oh good. I was correct and didn't give you bad info. :cheers:

Hopefully now you have the right info to determine the condition of the wiring and be one the right track to find your issue. 🤞

Well, That was more of a statement....AND....a question just to keep my own might right.

I'm already preparing myself (and potential parts list) of things I will most likely need and then things that should get done if the motor gets dropped.

Well, before I'd go dropping the engine I'd try some diagnostics on the wiring. Check for continuity, resistence. Check while you're physically moving the harness so if there is a break or issue in the wire you'll see varying values. Also check for +12V on the #3 with the igniton on. And even check for voltage on the wires that shouldn't have any.

If there's an issue with any of the wires you can run and splice it a new one without having to replace the whole harness.

So....checked things real quick. Don't know if this is right or not.

Ignition on
Coils all connected
Connector 5 at dme disconnected
There is 12v on the coil wires to the dme. For example green/blue (coil 1) and green/black (coil 4)

Since I'm getting the same on both banks I think it's normal

OK that's good. So that tells us there's a complete circuit from VS42 through each coil and to the DME. Did you try if there's consistent voltage while giggling the harness at various spots?

Another thing you may want to check is to diconnect the coils one by one and see if their respective wire still has 12V at the DME. To use your example, disconnect coil 1 and check green/blue for 12v. It shouldn't have any. If it does, it's shorting with another wire that carries voltage.

yup, wiggled the wires, pulled, pushed, etc. No difference.

On to the next test doing 1 at a time.

One other thought; Do you or anyone on here know if there's a cam sensor for each bank? If so, hopefully they are the same on both sides so you can just swap them and see if the problem follows. If it doesn't, then it rules out the sensor, but unfortunately it doesn't necessarily rule out that circuit.


EDIT: OK, so according to this Pelican article it does have 2 cam sensors:
https://www.pelicanparts.com/techarticles/Boxster_Tech/26-FUEL-Engine_Sensors/26-FUEL-Engine_Sensors.htm Check out figure 5.

Looking back at your OP there's no mention that you've changed it. If I understand it right, the cam sensor tells the DME when to ground the coils for a spark, based on the cam position. Maybe if the sensor sends a weak or irregular signal the DME doesn't complete the ground properly (garbage in, garbage out). The good news is that they are in fact the same on both sides, so you can swap them to see if the problem follows. Or maybe it's the crank sensor the signals when to send spark, I don't remember. But it's probably not a bad idea to swap the cam sensors anyway if they're not too hard to reach.

There is, but I'm not getting any cam codes only misfires.

Cam sensors are also brand new bosh ones.

So doing some onlie research, Cam sensors do a part to control spark. Crank sensor tells the DME what position the piston is in, while the cam sensor tells it whether it's in compression or exhaust stroke. Just because yours are new doesn't guarantee you didn't get a faulty one. If you can easily access them, it won't cost you anything to swap them and see if the problem goes to the other side. But then again like you said, if the sensor was sending an irregular signal, the DME would send a code for it. IDK. This is baffling.

Ok, here is a question for everyone.

What are the chances that all of this is being caused by gas? Specifically the wrong octane being in the car? Have a reason to ask cause I just had a Homer Simpson moment.

And I'll fess up. Went into the office this morning but needed to get gas first with the 03. Was distracted and put in 87 octane instead of my normal 91.

About 20 miles down the road started getting misfires on 1, 2 & 6. This car has never had an issue and it happening right after getting gas has me thinking.

Will be pumping out the tank in the 03 and putting that in the Jeep or the tractors tonight & tomorrow but it's really got me thinking the issue is fuel, fuel vapors/cannister...or fuel system related, just weird to get the same thing on a car that never had any issues. Given that its also not the car I usually drive it is very likely that 87 was put in the 00.

I tried 87 and 91 in mine and worked fine with both. Perhaps it`d matter with a combination with a knock sensor failure?