I'm having a bit of a stumble under boost and feels like it's pulling out timing or fuel possibly but unsure. I feel it could be one of the following but wanted to share these pictures to see if anyone thought this data/values was/were off or not looking like it should.

Possible issues:
- badf fuel... been awhile at the body shop getting repainted after years of scuffs and stone chips.. I decided to go full monty!!
- when the motor was out for clutch, reseal and other odds and ends (68k maintenance), I also had installed S-CAR-GO boost pipes and since they are thicker I couldn't use my new spark plug wire at #4 as the elbow or joint was much larger along with the boost pipe and it wouldn't slide past. So, this plug wire could be bad... Any ideas how to tell? I don't see any arching in the dark.
- I do have a flashed ECU from protomotive, running 1bar and has higher 5bar (instead of the factory 3bar.. I think) fuel pressure regulator.

Other than those items, I'm not sure as everything had been buttoned up and has driven 1,000 + miles with mostly no signs of this stumble. Occasionally there would be but then it would pass and drive fine.

Please have a look at the pics as I'm unsure what these values should be when correct. The car was fairly cold and idling for maybe 2 minutes.

Thanks for any help!! Otherwise, she's back after a slumber. Cheers, Bryan

 

I would probably start with checking the connection on the boost sender. Could be loose. Or maybe it’s time for a new one. https://www.stoddard.com/99360610301.html.html

 

Hey Bryan welcome back congrats on finally swapping out those after market rocker panels car looks 100% improved !
In so far as the real time data scan I really can’t give much input there has the car pulled a code as of yet ? Last O2 sensor change ? Thanks Bert

 

Thanks guys. No codes as of yet. I mean it could be the boost controller but who knows..

When I had the motor out I put in a new clutch and throw out bearing (a case of "while you're in there") and the throwout bearing is failing slowly, must have been a defective one... so the engine will end up coming back out at some point for me to address, but hasn't gotten any worse so no rush as of yet, just no long trips..

I was hopeful to find a solution beforehand so I know what will be needed. I'm guessing O2 sensors (if faulty) would be throwing a code right? That's why I was looking at live data as there isn't any codes so was hoping for some feedback on that information.

Appreciate the feedback thus far!

 

It'll be interesting to find out what problem you have.
My 993 Turbo behaves the same as yours. 50/50 if it stumbles or not at 4500-5000rpm.
I have now replaced the right turbo to intercooler hose as it was slightly broken on the turbo side. Also replaced the temp sensor on the ic. I forgot to put the connection on that plug this summer, and that resulted in the same stumble.
Car will not come out of my garage for testing before april/may due to snow

 

The O2 sensors if faulty likely won’t throw a code , if working will send correct data ..
just an idea … Bert

 

Bert thank you.

Appreciate the feedback. Finishing up another restoration on my 76' 912 then this will go under the knife for a couple months while I dive in and also change out the throwout bearing... not looking forward to this.

 

Well I think I found the issue... started up the ole girl and opened the engine lid to find #4 (as expected) arching right where it bends into the cylinder by the boost pipe.

This was the plug wire that wouldn't fit correctly due to the S-Car-Go thicker pipes in that area.

Anyone have a low profile option so I can change this one out?

 

Another update... Here is the plug wire that was in #4. This was the factory plug wire that I left as the aftermarket ones had larger elbows and wouldn't fit past the S-Car-Go pipe. Now, it's arching..

I'm tempted to buy a factory replacement and possibly go back to the factory boost pipe on this side.. Does that seem reasonable? These ones are so thick (I realize a good thing) but it hinders the plug wire from having any room in that area and makes it super tight.

Thoughts from others? See video above from last post. Would be great to have a shorter plug without the elbow so the wire could just come out of the valve cover and turn easier with more room... that's my thinking anyways.

 

Problem solved, drives like she's brand new! Took a while to get the #4 lead from Porsche but finally arrived and super happy it was something simple.

When it was arching the timing was being pulled out due to knock sensors which is a good thing!!! Now, just happy it didn't need something more invasive.