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I'm interested to know if anybody has come across this in their travels, I've not found anything here or in other forums. 991.2 GT3 with 15,000km, 3,500 on track, recently aware of noticeable drop in power especially at higher revs (>7500). No fault lights. My race shop checked as part of a regular track service, no detectable faults. They ran it on the dyno and saw an obvious drop in power with a sharp fall over 7000 RPM.
No clear engine fault, no misfires, plugs replaced as part of my service schedule, same problem. No exhaust restriction. Finally identified that a small composite plastic rod controlling an intake manifold valve was disconnected, and when reconnected easily fell off again. They dropped the engine and removed the intake manifold, to find (on the underside) that this rod would not remain attached. There is a second identical rod and intake valve which was fine: the rod was very firmly attached via its socket-and-ball connection but the faulty one was very loose.
The short story: new intake manifold installed, all reconnected, repeat dyno testing as we'd all hope to see.
The striking thing to me about this is that the rod and the coupling are not particularly robust, I find it hard to believe this is a rare problem, yet nobody seems to be reporting this that I'm aware. I'm very pleased with the detective work and hope that nobody else has to deal with it because it's a pain to fix.
Has anybody else here had this problem or have you seen it?
Some pics: Engine dropped, original intake manifold at top
Original intake manifold inverted, rod shown at top
Detail of rod disconnected from valve controller
Failed connection (circled) with internal intake manifold valve
Wow....great information, thanks for sharing. It's good to hear you found the root cause, and I wonder if you had a somewhat defective rod/connector, or whether we will start to see this as a regular failure with track cars?
Thanks for post. My 19 3RS has been suffering from exact same issue. I have been down on power on all track days last few months, same thing with no codes thrown but I can’t run fast laps and data shows straightline speeds are way down, the torque out of turns seems down as well (seat of pants guess). It has my dealer confused as the Problem cant be replicated except on track. Same as you with plugs changed with no improvement. It’s hard to explain that „my laps are 3 seconds slower and top speeds are 10 mph down on straights“ as they can’t replicate it. I will pass along this info as my RS is still at dealer investigating the issue yet again. Thanks
I thought I was going crazy – I was looking at my data and I was doing the right things but my times were ordinary and power felt down on the straights.
Next track day this Saturday, anticipating great times (ha!) because I've been working hard dealing with this rubbish for a few months and I should have a normal GT3 again
I'll have to pursue that. I'm not sure I would have trusted the dealer to identify this unless it was already a known issue. For one thing, they don't have a dyno and they wouldn't have believed my seat of the pants. Secondly, they have this bizarre yin-yang attitude when it comes to tracked cars, and it drives me spare: "These cars are designed to be tracked" / "you changed what to make it better on the track?"
Let’s be honest, the vast majority of GT cars these days are garage queens that accumulate most of their miles being driven to Cars and Coffees, so suspect not many will chime in here.
Let’s be honest, the vast majority of GT cars these days are garage queens that accumulate most of their miles being driven to Cars and Coffees, so suspect not many will chime in here.
I think that may be overstated as I know many GT owners who track their cars, but I get your point. I for one do fall into that group. I did my track work when I was a puppy on scooters (AMA Experts License in 250cc/350cc Road Race and raced at Daytona in '75) and I bought my GT2 RS just because after owning a 997 TT car I fell in love with the 911 Turbo cars and I wanted a GT2...and I could afford it so I bought her. But I don't want to expend the resources or time/energy to track her in a serious way and DE's don't really interest me but I do get great enjoyment out of just owning her and doing the occasional sunny day drive down A1A and to the occasional cars and coffee.
This was great info - thanks for taking time to share and add pictures, much appreciated! Haven't felt any problem but now I am even more happy that I took the warranty extension this year...
I think that may be overstated as I know many GT owners who track their cars, but I get your point. I for one do fall into that group. I did my track work when I was a puppy on scooters (AMA Experts License in 250cc/350cc Road Race and raced at Daytona in '75) and I bought my GT2 RS just because after owning a 997 TT car I fell in love with the 911 Turbo cars and I wanted a GT2...and I could afford it so I bought her. But I don't want to expend the resources or time/energy to track her in a serious way and DE's don't really interest me but I do get great enjoyment out of just owning her and doing the occasional sunny day drive down A1A and to the occasional cars and coffee.
No judgement here, but this might actually be much commoner than known. It throws no codes and is not detectable with routine computer diagnostics. It’s only apparent at high revs or when the car is on a dyno. I don’t even know if it’s harmful apart from the loss of power but somebody might be able to clarify that for us.
My intake manifold went bad on my 992.3 engine (Speedster, with ITB) in Mid July. I did have an 'Engine Control Fault - OK to drive on', but I was 5 minutes from the dealership so I took it in. We've been waiting for a replacement manifold from Porsche ever since...going on 4 months...frustrating, but I'm hopeful for a resolution very soon....
Just bumping this because I'm 95% sure my car has had the same failure. Zero fault codes but high RPM power is a goner, it really doesn't want to go anymore between 8 and 9K compared to previous. Totally normal at low/mid RPM.
Can't believe how cheap this part is built. Tracked down a used one for $150 fortunately. If the Dundon guide for their plenum is anything to go by it can be swapped without totally taking the engine out.
Honestly though I can see some people who aren't as sensitive or hard driving to not ever notice this failure.
10-28-2020, 10:24 PM
Intake manifold fail
