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Issue: 2007 987 Cayman 2.7L won't rev above ~3.5 thousand rpm. Issue arose midway through a bucket seat install however those systems should be completely unrelated. Car still drives and everything works it just only with super low revs(very fun to get going on even a slight incline btw) Car also has a PSM yaw module ground disconnect switch for true PSM off capabilities on track days.
Troubleshooting Attempts: New accelerator pedal, Durametric scan from mechanic showing several codes only related to the throttle body, Install of IPD plenum and GT3 throttle body(if im gonna replace it might as well upgrade), Throttle body reset procedure, battery disconnect reconnect, etc, Different mechanic had it for around a month, tested all the electrical connections, and came up with nothing
Ideas: Replace faulty clutch safety switch, Resolder PSM ground disconnect switch out of the system, ECU flash??? Really not sure where to go from here as it feels like I've tried everything and I'm not sure what still needs to be replaced. Any ideas help and I'll answer any questions to the best of my ability.
Your first post. Welcome to Rennlist!
I have no immediate suggestions but am curious. Is it a hard cutoff like with a rev limiter and is it soft? Does it always occur at the same rpm regardless of load?
BTW, your title is mis-leading. If the symptom is that it won't rev over 3500 rpm why do you think it is throttle body relearning?
It's a soft cutoff persisting as if the engine is not getting enough air even with the throttle flat to the floor. I checked the entire intake system and it was clear all the way through. We believe it's the throttle body relearning because I attempted to do the procedure several times with the key in the ignition and everything while visually observing the throttle body not doing anything. Tried manually manipulating it as well as I heard that is an option. I believe the second mechanic that had the car also attempted the procedure whilst directly connected to the computer and it still did not reset. While I can't observe the throttle body as the car is running because MAF and stuff like that it feels like for whatever reason one of the times I disconnected the battery whilst removing the seats, the throttle body started only opening about halfway or so, even at full throttle. So maybe a short somewhere in the engine computer?
Was the issue happening before the aftermarket plenum and GT3 TB install? I would revert to stock first, those “upgrades” aren’t going to do anything for your 2.7.
I would have to agree with @RJ80 Go back to stock and work forward from there.
I have a 2007 Cayman S engine on the bench right now. Per the picture below, if you were to remove the ribbed tube (from the AOS) on the right hand side of the plenum downstream from the throttle valve, you would be able to get an endoscope in there and see what the throttle is actually doing. This will generate a massive vacuum leak so you will need to seal around the endoscope and also close off the disconnected ribbed tube from the AOS to allow the engine to run normally. Otherwise, you are just working on speculation that the throttle is not fully opening.
I have also attached a vacuum diagram. Interestly, Porsche dropped the vacuum diagram from the sticker on the engine cover between 2006 and 2007. This sticker is from a 2006. As noted above, I would go back to stock and make sure all these vacuum connections are made up correctly. This diagram is for an S engine but I suspect the base engine is the same. BTW the chaneover valves are mounted in between the intake runners, one on each bank. They have a mechanical function and electrical function. They control the resonance flaps. I don't think the action of the resonance flaps could cause a 50% drop in revs but who knows, if they are not working, maybe that is confusing the ECU.
In general "learning" means the systems can adjust for long term degradation of components. I would be surprised that it would result in such a massive performance impact as you are experiencing. But it is hard for all of us to know how Porsche has designed the software. To paraphrase an old parable, we are all touching different parts of the elephant and drawing our own conclusions.
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