iflyjetzzz

I had acceleration problems (car not accelerating) when I pushed on the gas pedal. This was accompanied by the cruise control not working.
Turning off the ignition and turning it back on would clear the problem.

I had a mechanic replace the fuel filter and low pressure fuel pump. All was fixed. For a week.

This morning, I was driving and while my car accelerated, it did so slowly. I tried to turn on the cruise control (to confirm interrelated problem) and it would not turn on.
I turned off the ignition and back on, and everything worked normally again.

High pressure fuel pump failing? Other ideas?

No caution light. I will check for fault codes but it didn’t have any previously.
2007 Cayman S 6spd.

MrMoose

That's a weird one. Link to the cruise control makes me wonder if it's some issue with the gas pedal itself? It's purely electronic, so weird stuff can happen. No guarantees, though.

I'd try pulling the codes again regardless. You've got a 987.1 which is non-DFI so you don't have a high pressure fuel pump.

iflyjetzzz

LOL! I thought about that after posting - no HPFP.
I gotta hook up the ODB2 and see if it throws any codes this time.

From digging around on the internet it may be the clutch switch or brake switch causing the cruise control problem.

Dave in Chicago

There are two switches on the clutch, as I recall, one to ensure the clutch is depressed for starting the car, and two one exclusively used by the cruise control circuit to disengage when the clutch pedal is depressed. I had to replace the second one on my car as it would randomly Cut out cruise from time to time turned out to be that second switch.

iflyjetzzz

P2126 Throttle adjusting unit potentiometer 2.

Also threw (I'm assuming unrelated to problem)
AWS Control
C128 (No signal/communication) Communication PAS (comfort) control unit
C131 (No signal/communication) Communication gateway control unit (CAN unit)

Gateway Control System
C140 (No signal/communication) Communication instrument cluster (display)

PAS Control System
8004 lower limit value exceeded Terminal 50

PCM Control System
C140 (No display) Communication instrument cluster (display)

POSIP Control System
C158 (No display) Communication gateway control unit (CAN drive)
C140 (No display) Communication instrument cluster (display)

PSM Control System
4444 (No display) Steering-angle sensor not initialized
C140 (No display) Communication instrument cluster (display)

Seat Memory Control System
C102 (Implausible signal) CAN single-wire operation comfort

iflyjetzzz

Thank you very much for the reply.
I'm now not sure that's the issue, as I couldn't even get the cruise control to turn on (green light didn't come on) when I was having acceleration problems.

Throttle body needs to be replaced? Opinions?

iflyjetzzz

This sounds very similar to my problem: https://rennlist.com/forums/997-foru...ses-power.html

MrMoose

Yeah, as noted above, from a quick search that appears to be a pot in the throttle body, and you may need to replace the throttle body.

iflyjetzzz

Just a quick update.
As stated in first post, low press fuel pump was replaced by an indy.
Problem solved for a week. Problem returned once so far, but not as bad as before (car slowly accelerates vs staying stuck @ ~800 RPM).
If I can't turn on cruise control, I know the problem has returned. So far so good.

Narrowed down to 3 possibilities, brake switch. Clutch switch, throttle body (potentiometer). Throttle body most likely.

Brake switch is easy and cheap replacement so I just bought one at the dealer. Will replace and see if I have any additional problems.
i also read that a dirty engine air filter could bee messing up the throttle body so I'll also replace that.
If the problem's not resolved, I'll get a new throttle body. I'll wait until the problem reoccurs.

Edit/update: Took the car for a nice leisurely drive to the Porsche dealer today to get a Brake Light Switch. Also picked up an engine air filter due to the nice military discount.
Changed out the air filter (will try to attach side by side pic)
Changed out the Brake Light Switch - not nearly as easy as the youtubers made it sound. I'm sure it was an unnecessary thing to do but the part only cost me $30 plus a bit of aggravation changing out the parts.
Got a quote from an indy for throttle body replacement - $610 plus tax. I may end up doing it as a home project; debating that.

It was nice to take the car for a drive to somewhere other than to/from work. The drive put a smile on my face ... listening to the engine's growl at 5K RPM made me very happy.
No acceleration problems today. I will just continue to monitor the problem and if it happens again, it will be time to replace the throttle body.

iflyjetzzz

Quick update for those that reference this thread in the future. No further problems with acceleration and my cruise control has turned on and engaged normally. I expect this issue to pop up again because I don't expect the things I've done to have resolved the problem, but with the way things are interconnected, maybe that did it?

To recap:
Had fuel pump replaced.
The problem occurred once after the fuel pump replacement, but instead of no acceleration (before the pump was changed out) the car accelerated like it was an underpowered Nissan Versa (if you've ever rented one, you'd know what I mean).
I then changed out the Brake Light Switch and engine air filter.
I cleared the OBD2 codes and drove the car.
All except two codes cleared; the remaining ones are unrelated:
POSIP Control System C152 Comm PSM Control Unit
Seat Memory Control C102 CAN single-wire operation (Comfort)

I'll update this thread if I have the issue again. Of course I'll also pull the OBD codes and if P2126 returns, I'll change out the throttle body... I am expecting P2126 to return. If I have the same problem without a P2126, I'll change out the clutch switch. The clutch switch is a cheap, relatively easy fix. The throttle body replacement is a bit more work.

iflyjetzzz

I had the slow acceleration again today. I checked my cruise control and was unable to turn it on. Turned off the ignition and turned it back on ... the problem cleared.

When I got home, I checked codes with my ODB2 and the P2126 code returned.

I ordered a new Bosch throttle body and O ring this evening from FCP Euro; parts will be here on May 2. I will update this thread for others a while after I replace the throttle body - whether or not this solves it. I expect this to be the solution.

iflyjetzzz

Replaced the throttle body today.

I'm not throwing codes but it's idling rough now (wasn't idling rough before I worked on the car) so I'm 99.9999% sure I've got an air leak and need to redo my hose connections. What I PITA.
I'll redo my work tomorrow.

MrMoose

There's a throttle body calibration that needs to be done. Durametric can do it but I believe there's a way to just do it manually: do a search and try that.

iflyjetzzz

Thanks for the post. I think that my 2007 is too old to have that feature, but I did leave the ignition on for a few minutes before I started the car. I had read about Porsche throttle body calibration and that seemed to be the general solution. I've also seen where some reference a Durametric calibration, although I suspect that's only for recent vehicles. There are also comments indicating that it takes up to 100 miles of driving to calibrate.

The hose connections for the air intake system are a bear and I suspect I've got at least one leak on the bottom of one of those connections. I'll remove the connections and lubricate the connection points to try this again.

harveyf

Regarding the hose connections, you are right. I don't know what the pros do but there doesn't seem to be any usable slack in the rubber hoses. I disconnected mine at the connection between the air mass meter and the throttle body but it did not want to come willingly. This was during my engine rebuild. Going back in, I got it started with the engine some inches below the lined up position and that helped. Not much help to you though.

The old school trick is to spray something like starter fluid at the various potential leak points and see if the engine speeds up.