Question about ground point at left rear of engine

Hello, I am doing some troubleshooting and I was wondering if someone can help me locate a ground point. Specifically, I am looking for grounding point #11. This is the ground for ignition coils for Cyl 1-3. According to the manual it is at the left rear of the engine compartment. Here is the description in the manual (GP11) as well as the top down view on the car. This still does tell me exactly where it is. Anyone have more detailed info or perhaps a picture?

I could stand corrected but I think it is located on the back side of the engine near the wiring loom for the crank position sensor (CPS). Brown wires bolted to a ground point.

DBJoe996, Thanks for your response. I should have mentioned it, but I am dealing with a 2002 model year, so 996.2. The crank position sensor is on the left side by the transmission (not sure if we want to call that the front or rear of the engine). It would be roughly around where GP8 is. GP11 is shown almost at the bumper.

Is this it.

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I'm curious too, as I've never noticed a ground from the engine near GP11, as on the map above. hbdunn, your pic is of a 996.1, which may not matter, but also at the front of the engine more near GP8. I see the CPS, and the cam sensor, but is there a ground point there somewhere? Thanks! Edit: Ahh, I see a ground to the block. But the block is still grounded to the frame through the single point on the passenger side though, right?

Thanks. I see the ground point to the left of the yellow arrow. However, this is a 3.4L engine. I am working on a 3.6 engine and the diagrams that I included are for 996.2 car. I can't find a similar picture of a 3.6L engine, but from my experience in working on mine in that area I don't think that there is a similar ground. There must be one that grounds the 3 injectors on this side of the block, I just can't seem to find where it is in a 3.6L engine.

Ground point 11 is for ignition coil 1, 2 and 3 per my wiring diagram Ground point 10 is for 4, 5, and 6. Check page 17 of my upload attached...

e30rapidic, Thank you for the diagram. I know that this ground point is used for these coils, that is why I am looking for it. My problem is finding it. Where is it physically?

When I had misfire problems two years ago I connected the bank 1 ground point� it didn�t help. I did LOTS of tracing & troubleshooting. The only thing that fixed the problem was replacing the coils.

dporto, can you tell me where this ground point is?

I'll look in my engine out photos... hmmmm....look under the AOS, behind the crank sensor connector...that may be it?

The Porsche factory wiring diagram is wrong, are ya having fun yet?? The picture above is the ground you are looking for, GP10 and GP11 are on the engine not the body rear..That is GP11 , GP10 is near the A/c Compressor.... I was Top Troubleshooter in the Southest for FoMoCo for a couple of decades, their technical info was much more faultless than Porsche , Porsche is really a "mom and pop" company compared to FoMoCo...

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If you�re looking at the rear of the car, from behind it�ll be on the left side. IIRC it�s tapped in the head (but maybe the block just below the head - It was a few years ago so a little hazy�) M10 bolt? (Same as other side)� Like I said, it didn�t fix my problem, but I figured it couldn�t hurt at the time. Now I�ve got two ground points from the motor to the chassis�

Thanks dporto and Porschetech3. Disappointed that I can't always trust Porsche wiring diagrams, but I guess this is just what it is. I will look behind the AOS. Doesn't look particularly accessible with the engine in the car.

Not near the AOS� closer to the rear bumper�

OP, take a few pictures of the approx. area and post them here for those in the know to mark where the ground point is. I think that would be a lot quicker...

OK, so I have an update. So I can confirm that this ignition coil ground connection is on the engine cylinder head not the body as the wiring diagram indicate (thanks Porschetech3). Now that I think about it, it doesn't make sense to put it on the body. The wiring harness is attached to the engine, so makes sense to attach the ground to the engine as well so that they can all vibrate together. If this ground would attach to the body, then the wires would always be flexing a bit when the engine vibrates, and therefore more likely to break. Also, it would potentially limit lowering the engine. Lastly, I also figured that if this ground attaches to the body then there must be a step in the engine removal instructions to disconnect it from the body. No such step is in the factory manual for engine removal. Here is the picture of what I found in my car. As you can see the ground connection is attached by the bolt holding the crankshaft position wire bracket, not the proper location, which according to the picture in post #11 is about an inch below that. Also, as you can see my bracket is very rusty as is the bolt holding it. I was barely able to get to this bolt and remove it. Lets just say it is not particularly comfortable doing that with the engine in the car but I was able to get to it with a flexible 10mm socket. I used sandpaper to clean the islet on the ground wire connection and I wirebrushed the metal bracket as well. I also sanded as much as I could the contact point on the aluminum cylinder head and put it back together. Ideally I would install this ground where it belongs, but I simply couldn't reach it and get the bolt started with the engine in the car, so had to go with what I could manage. I also put some deoxit on the contact surfaces for good measure. I still doubt that this is the cause of my misfires, but it was a "no parts required" project, so I figured worth doing. I drove the car yesterday for about 20 minutes and as expected everything was fine. However, that doesn't tell me anything because that is how I expect it to be without doing this. On average it would take 150-200 miles of driving to actually register a misfire, so it may take a while to confirm whether this did anything or not. I will revert back to this thread with my findings in the future.

That is where the ground was installed from the factory. The diagram is wrong.

Amargari, thanks for your picture. What is interesting is that there seem to be differences in our cylinder head castings. Looking at your picture and post #11, there is a protrusion cast next to the intake cam (circled in red below). However, looking at my cylinder head I don't see that protrusion. I didn't know that Porsche changed the casting on this cylinder head during production. Not sure why they would make this change.

The protrusion is there, the CPS wiring is mounted to the protrusion on the last pic.

JohnCA58, If you look closely at the picture of my engine in post 17 you will see this protrusion is absent. Don't know why, but that is what surprised me.

you need to look closer to the location of the bracket to the AOS body, the bracket is in a different location in either picture. in the top picture the injectors ground are separate from the CPS wiring bracket, and in the last picture the CPS wiring bracket and injector grounds are using the same bolt. same heads. I am guessing the last guy to work on it misplace the bolt for the bracket and decide to mount it with the injector grounds.

The difference could be that I have a 3.6 and you have a 3.4. They are different heads.

amargari, this is the puzzling part. I have a 3.6 not a 3.4. Mine is a 2002 model, 3 chain engine.

3.6 I believe untouched.I have this engine out ,if you or anyone need so pictures feel free to ask.

My 2002 (was 3.6) also appears to not have that protrusion.

Mpfaff and TexSquirrel. Thanks for your feedback. Mpfaff, if I interpret your picture correctly, then I see your head has a protrusion but it is not threaded. Therefore both the bracket and the ground point are attached at the same spot. And TexSquirrel confirmed the same thing that I saw on my engine, some heads have this protrusion and others don't. Mine is a 2002 and also doesn't have it. Looks like for some reason Porsche changed the casting on the head at some point during production. Seems like a very minor change, but I guess they decided to split the bracket and ground point to two different attachments from one. Anyhow, I don't think that matters all that much. On mine the ground point was mounted on the outside of the bracket (meaning there was a rusty bracket between the ground point and the cylinder head) and I reversed them to be the same way as what Mpfaff has (so the grounding point is in direct contact with the aluminum head, plus I sanded all the contact surfaces and added Deoxit). I'll report if this makes any difference.

I got sort of intrigued by this and looked at a bunch of 3.6 engines on ebay. Both banks should have the protrusion, Bank 2 is threaded and that's its ground point. Bank 1 it's not threaded and the ground point is the CPS bracket.

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I would think bank 1 is the one on the right correct? It looks like it has it.

I may be wrong, but I believe both banks are cast the same but are machined differently for the heads.

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Bank 1 is on the left and Bank 2 is the filthy one on the right.

There were a few different castings used for 3.6, the biggest difference is between VIN split at engine # M >> 663 09950 where as the " before" has a 1 bolt connector for the AOS breather pipe on bank 2 and the " After" has a two bolt connector for the AOS breather pipe on bank 2 ..... 1 bolt connector 2 bolt connector

Well, a quick but disappointing update. I cleaned this ground point, then drove the car for a week and a half. Everything was fine for that 10 days, and then yesterday again, I come to a light and the car is giving me a horrible misfire, cylinder 2 and 3. Check engine light flashing, engine shaking violently and dies on its own at idle. I am stuck in the middle of the street with people going around me. Figured I am using my AAA membership to get home. Nope, I waited a few minutes, the engine restarted. It wasn't happy for the first few seconds and I had to give it some gas to keep it alive, but then it smoothed out and ran fine. I got home under my own power. Unfortunately I still can't diagnose whether the engine is losing spark or fuel. I hooked up my durametric and checked timing, it is perfectly fine (bank1 is actually only 0.2 degrees out of time and about 1.8 degrees on bank 2). I am pretty good with my PicoScope. I can hook it up to the ignition coils or the fuel injectors at the DME, but all that is useless because I can't figure out how to trigger the misfire. Most of the time the engine runs perfectly fine. I found a long wooden rod and tried poking at parts of the wiring harness that I could reach with the engine running in my garage, hoping that if there is a bad wire somewhere that I can trigger a misfire that way, no luck. At this point I am thinking that DME should be the next item to blindly replace because I am out of diagnostic ideas. I am hesitant to sent my DME to be refurbished because even if it has a problem, it is so intermittent that my DME will test just fine 99% of the time. I am thinking that a used DME may be the best option. I can pick one up on eBay for relatively cheap, but I know that it needs to be coded. Anyone know someone in the Connecticut/NY area that can do this? Just in summary, parts that I replaced already are: coils, plugs, intake valve lifters and cylinder 1,2 and 3, all 6 fuel injectors, variable valve timing solenoid, valve lift solenoid, and I cleaned the ground point for ignition coils.

Used DME, your immobilizer, and your key fobs have to be coded together. Only place I know that can do that with a used DME is ECU Doctors. https://www.ecudoctors.com/collectio...-996-2000-2004

Hello Boris1, I was wondering if you ever were able to figure out what is going on with your Porsche misfiring. I found this thread, and created an account just to chat because I am dealing with the same exact problem in my 2015 Toyota Tacoma. I have replaced: Injectors, Coils, Plugs, Upper and Lower Intake Gaskets, Throttle Body Gasket, PCV Valve and Hose, Battery, Fuel Pump (FPR, and Filter included), Cam Position Sensors, Crank Position Sensor, ECM Tests performed: Exhaust back pressure, Compression, Swapped Upstream O2's, Swapped Injectors (after replacement), Swapped Coils and Plugs, Cleaned 4 engine grounds with a wire brush, Grounded battery to engine with jumper cables to ensure good ground. When I run a live scan and record it my fuel trims operate inversely of each other as well exactly like yours and then I will get a misfire on my Cylinder 2. (V-6 4.0) Cyl 2 4 and 6 are bank 2 with 1 3 and 5 on bank 1 and all my Misfires are Bank 2 (P0300, P0302, P0306) 4 normally does not misfire for me but will record one every now and then. I thought purchasing a Picoscope would be the savior of my problems but you own one and still nothing is showing up....!?! I'm pretty desperate at this point for answers (clearly) as I was close to breaking my entire engine down and replacing head gasket and valves to see if that would fix the issue.

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https://www.tacomaworld.com/

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Yeah, tried that for 6 months. I'm asking a man who has the exact same problems with an OBDII VVT engine. I just want to read the end of Boris1's story. Because like i said I'm in dire straits right now and he is not on Tacomaworld. ​​​​

@Boris1 After 6 months I figured it out. This is on my truck but it's bound to be thr same on your Porsche given the symptoms. Unplug your VVT solenoids and give it a drive. Make sure to check and clean filters before reinstalling new ones.