Well hey there 958 Forum. Just picked up this 2014 CD with 68,000km on the clock (42K miles) in Mahogany Metallic. There's a couple issues to work through -- the normal start-stop problems and wet lower front engine. It's a Chilean market car, and, as far as I can tell, no dieselgate warranty and no ad-blue system (no tank under the spare tire). It's joining my recently purchased 2010 Cayenne Turbo and my longtime 968 Cabriolet and is destined for daily driver duties.

I look forward to learning about how best to maintain this diesel beast (my first one!) and sharing my adventures with you all.

 

If it doesn't start stop then it's usually a battery that's not strong enough or the aid conditioner is running or the sport button is pressed. Read your manual.

 

I'm sure it's the battery that's the issue. It's weak on regular start as well. Supposedly it's "new", but since the car largely sat since 2019, it's probably not. Or if it is, it's not the correct size. I'm having a devil of a time finding the correct size replacement here online. From what I've read Varta is OEM, but it seems unlikely I'll find that. Closest I could find in terms of specs is an AC-Delco AGM 105Ah 720CC. But the size seems huge in comparison, so I'm going to have to pull the seat and then do some foot work in the local auto shops to see what I can come up with.

 

After receiving my new buffer, I went through the paint correction process on the car. It's not perfect, but it's much better than it was prior! I'm loving the mahogany metallic paint - such a cool color.




Cleans up pretty nice

 

So I did my first service on this last night and got a chance to give it a good inspection underneath. There's a lot of built up grime on the bottom of the engine, above the oil pan, and some oil wetness near the back of the engine and on what I'm assuming is the oil level sensor. Nothing too concerning yet, thankfully.

The oil change went ok, but I miss the dipstick for immediate feedback on oil level. Also, I learned the hard way to check that the rubber gasket on the fuel filter is well seated - I ended up with diesel all over the engine bay and under the car. I'll definitely know to check that well the next time! Cabin air-filter wasn't too hard, and the engine air filter is the same as my 2010 Cayenne, so that's cool.

 

It's the little things that make me happy.. Rennline phone mount installed and USB-C charge cable routed invisibly from a quickcharger in the passenger's footwell.

 

Mahogany Metallic looks good on the Cayenne and Cayman/Boxsters, something about the curves that just do that color right. Speaking of color, what color is your 968?

 

968 is Midnight Blue. Original color, but a reasonably good repaint. The 957 is Meteor Gray Metallic, which is also a pretty nice color on the Cayennes.

 

First few non-regular maintenance items..

Found the cause of my slow starter and non-working start-stop. Bad engine ground strap. With that replaced with a brand new strap, all is well. Just for grins I autopsied the old one to see what failed with the old one.


Engine side, old on top, new on bottom. Old looks fine.

Chassis side, Old on top, new on bottom. Old has clearly failed, glue drops squeezed out the bottom.

Taking the heat shrink off the old reveals corrosion on the crimp

Old heat shrink shows clear signs of moisture intrusion.

Old insulation got hot at some point.

The corrosion extends up the wires.


I reinforced the new strap with multiple layers of heat shrink and electrical tape to hopefully prevent future failures.



Reinforced the new ground strap to help prevent moisture from wicking up the heat shrink.

 

The next, more serious problem manifested itself after some heavy rain with a speaker going into BugZap mode at full volume.


Traced the problem to water ingress into the rear cabin due to, yeah, you guessed it, clogged drains. I've cut the pinched ends off the drain hoses to hopefully prevent future incidents.

That front right channel is now dead and only produces annoying static. I took the amp out to see if I could revive it, and found lots of corrosion but a good clean didn't help the situation.






I've decided that instead of repairing or replacing the original amp, I'm going to upgrade to a Match Up 8DSP amplifier. From the sources I've gathered online, I think I should be able to make an adapter for the wiring harness and plug it in as a pretty much drop in replacement for the Base Audio

 

I got the Match Up 8DSP installed and tuned, but ran into some issues. However, even with those issues, holy hell did it improve the sound of the standard PCM system. Much tighter bass, real stereo separation and better clarity from the highs. I can't recommend it enough. That said, let's talk about the issues.

1) The biggest was a mistake on my part - the amp is expecting a high level input, but the PCM 3.1 only outputs low level. This is a problem, as it means I have to crank up the input gain to get any sort of volume out of the system, and when I do that, I get an awful white noise hiss. I've played with the settings on the amp the best I could and got something decent out of it, but the hiss is still there. My long term plan (if the PCM in my car supports it), is tap the MOST and send that into a MOST to Toslink converter, then run the Toslink to the amp for digital audio. It's a PITA and a bunch of extra cost, but I think it's the way to go in the long term.

2) The front passenger woofer seems to have burnt out. I haven't pulled the door card to check, but the wiring at the amp is correct, so I can only assume that's what happened. So I'm going to need to find either a stock replacement speaker, or go for an upgrade.

Those are the biggest issues. For the install, I just ripped the connectors out of the old amp and soldered them directly to the harness that came with the 8DSP. If I ever want to go back to stock (not likely at this point), I can get a factory amp. To physically mount the amp, I drilled out the center hole on the top of the amp to the correct size, then modeled and 3d printed a bracket for the bottom.



3d Printed bracket and wiring harness.

Installed in the car.

 

After some initial messing around, I finally got the conversion to fiber done, so now I've got digital audio from the Non-Bose PCM unit to the amp. I had some initial problems with no audio appearing and I feared it'd need a code to enable the fiber output from the PCM, but after it fully shutdown and rebooted, I had audio output. The converter I bought is a Helix SDMI25 (discontinued, but I found a shop with some in stock here in Chile). If someone comes across this thread and wants to do similar, I think the mOBridge DA1 offers similar functionality. For the cable, I purchased 5m of fiber optic most cable from a chinese seller on ebay and ran the it down the passenger side of the vehicle, just tucking it under the trim. Then I've got a TOSLink cable from the SDMI25 to the Match Up 8DSP


Testing phase = the orange cables are the fiber optic. I ran with it like this for a week until I finally had a chance to do it properly.

The SDMI25 is stuck to the back of the amp. I taped the fiber optic cables every 20cm to keep them in order



At the same time I ran 4awg power from the battery to the amp, so now it's no longer constrained by the factory wiring harness. The stereo now sounds really good, even though it's still missing the passenger woofer.


Good 4ga wire. Ran it under the drivers side trim to behind the back seat, then across to the amp.



50A fuse, Amazon special, pure Chinesium.



Same gauge ground wire from the amp to the body ground right below.

 

I've got some vacation time, so took the opportunity to give the diesel some TLC. I've seen the horror story pictures of the EGR valves clogged with buildup, so I decided to open it up and see how bad mine was.





Not bad for 90,000 km (56K miles), but not great either. 2 cans of Brake cleaner and 1 and 1/2 cans of Carb cleaner later, and it's looking good to go for another 90k kilometers.

 

I want to clean mine before I get it tuned. Was it difficult? Anything to look out for?

 

Not difficult at all. 4 or so 5mm hex head bolts, a bunch of t30s, and flat head screw for the intake hose clamp and it's off. I used the video as a guide: