GT3PDL

Went to Barber this weekend with my Father-in-law in our GT3's as we regularly do, his is a 2019 GT3RS that he has owned from new and is predominantly a track car. He now has about 7500 miles on the car and besides the initial break-in miles, and the miles to and from the track and dealership for service, they are all track miles. The car has developed a misfire type issue that has progressively gotten worse over the past two track events. The car runs as it should under normal conditions, but now under full load at around 7k-8k RPMs it has a power cut/blip that is happening a couple of times a lap, more in auto mode than when manually shifted. I drove it on track to try and help diagnose the issue and can't tell if the engine is cutting power or if the transmission is mis-shifting? It is similar to the feeling of hitting the rev limiter, but a little more violent. It also occasionally shifts rougher/harder from time to time, but only in random occurrences. This only happens under full throttle acceleration and about 1k RPMS before it would normally shift and is not gear dependent. My father-in-law originally chalked it up to be a transmission issue and took it to the dealer before this event, but it is not throwing any codes so there was not much the dealer could do since they can't duplicate the problem on the street. The dealer changed the trans fluid and reprogramed the trans TECU hoping that would correct the issue, but it did not help. He had his engine air filters cleaned and reoiled around the time this started to happen and we are thinking they could have been overoiled and allowed residual oil to get on the mass air flow sensor or maybe it could be a spark plug issue since they are certainly due for a change, the car is almost two years old with plenty of track time. It just got back to the dealership today and they are going to change the plugs, check the air filter, and mass air flow sensor, but we are not really sure what else they can do without any active codes and no way to duplicate the problem. Has anyone out there seen or heard of a similar issue on a .2 3RS? Thanks in advance for your help!

flyjets

When this happens on my race cars it's usually plugs. But it can be a coil or other ignition issue.

Ian

usrodeo4

My guess would be coils...maybe a cracked one?

Richard.

indeed coils

kevrenmorland

That is the exact issue I was dealing with all summer. I changed plugs, and coil packs and that didnt work. I re-flashed the ecu to factory settings, and that didn't work. Then, the dealership had me replace my ecu even after re-flashing, and convert my exhaust back to stock and and that didn't work. It finally ended up being a cam speed sensor. They said it was only the second time they had seen a sensor not throw an error code but cause that issue. The problem is identical to the problem I was having, including the RPM range of the issue.

GT3PDL

That's great info Kevin! I appreciate the feedback and will ask the dealer to check out the cam speed sensor.

991carreradriver

While I agree with the previous responses, would not a failed plug, coil or cam sensor failure be evident via PIWIS, when the ECU was dumped?

Quikag

Spark plugs.

tgibrit

I had an issue with the transmission on my 19 RS, intermittent and only happened on track - almost like the clutch was slipping. in the end they recalibrated the PDK and that seemed to work, but the point of this story, is that I was using thee Porsche track precision app that clearly showed the issue - which the dealership then shared with Porsche engineering. As you are in the SE and may still get to the track this year, this might be worth a shot as you will have video and data.

GT3PDL

Thanks tgibrit, that's a great idea, wish I had thought of that this past weekend, but will definitely give that a try if they are not able to resolve the issue on this current visit to the shop.

s4corrado996tt

Good luck! Hope you resolve it soon! Let us know what caused it. Thx!

KA 991 GT3

I just had this happen to me on my 2018 GT3 with 4500 miles on it. It was coil on Cyl 1. Tech changed it and all good. I had them do the plugs as well while at it. Some of the boots are sticking to the plug causing some issues. They had to replace one boot on a diff cylinder as well.

GT3_Driver

Any codes to look for?

GT3PDL

Just wanted to update this thread, I was finally able to get this car back on the track over the weekend after the dealer changed the cam speed sensor as kevrenmorland suggested. I'm happy to report that the cam speed sensor was indeed the issue and the car never skipped a beat. I really appreciate the tip from kevrenmorland as this really helped us solve the issue. Thank you!

kevrenmorland

I am so glad that helped you out. It was frustrating to go through the trial and error process on mine. Now we know it is a reoccurring problem with that sensor.