Dead throttle pedal...what's this?
 

05 base car, 71K miles. Three times today, driving along at slower speeds, the throttle pedal just stopped responding. I pumped it a few times and it started to function again. No pattern that I could discern. By coincidence, I was watching the tach during one incident at it seemed like the revs did not drop (odd I thought..). Each time it lasted 2-3 seconds. Any ideas?

Check this out
https://rennlist.com/forums/997-foru...continues.html
Seems to plague 2005 vehicles

Thanks for the reminder ajayabb! I remember reading your thread but it had fallen into the dark corner of my aging brain. I'll use this for my tech to follow.

Good luck. Keep us posted

any codes being thrown? my guess (in this order) is: brake switch...throttle pos. sensor in pedal...TP sensor in TB...MAF.

please report back when you solve it!

Thanks spiffyjiff. I will report. I don't have an appt yet for the car to be checked, so no codes. Appreciate the input.

tentative positive follow up...
 

After reading the referenced threads about the brake/clutch and clutch lock out switches, I decided to replace all three of these myself as a relatively cheap way to eliminate them as the cause. I was getting the dead/non functioning pedal more and more frequently, in some dangerous (pulling out into traffic) situations.

I replaced them last Saturday, about 4 days and 100+ miles ago. I've driven in town, freeway, cold/hot, etc. and the issue has not returned. Because it was cheap (about $80 for the three switches) I'm paranoid that it is too good to be true, but so far so good.

I have to add that the changing of the two plunger type switches appears easy and should be, but was definitely a challenge. The space under the dash was impossible for me to get pressure behind the switches to seat/turn them. The clutch lock out switch (at least in a base 05 C2) was impossible to remove without taking the bracket off first. The small phillips screw is only accessible with a flat profile ratchet driver, maybe 1/2" space there. The nut on the back side of the mounting plate is welded to the plate, so you cannot do it from the exposed side. If the access was available to get to these things, it would be a 5 minute job. As tight as it was, it took me about 45.

Hello All,

I am having the same symptoms on my 2005 997 C2S manual.

Having read this and the 'throttle saga continues' thread I was wondering if someone could point me in the right direction given the following extra observations.

Throttle becomes unresponsive until I either dip the clutch release the accelerator and try again.
This fault still occurs with PSM switched off ( tried that test this morning - still fault occurred ).
At the weekend cleaned the MAF and the Throttle Body to no avail.
I have tried left foot braking whilst driving but this doesn't seem to create the fault so am doubting whether it could be the brake switch.
I have no stored codes shown on my OBD diagnostics

So can anyone suggest what it is most likely to be please?

I have a new ABS wheel sensor on order and a new brake switch.
Could it also be the clutch switch?

I was going to start with the brake switch but maybe I should get a clutch switch too.

Any help would be much appreciated as have had the car since February and the fault seems to be getting more frequent.

Regards
Andrew

no codes at all?? wow that's odd (and unfortunate) that it isn't throwing codes that would help diagnose. if you have a durametric, maybe you could log while driving and hope it occurs again? you might be able to tell something from the data before vs. after.

also, when you say unresponsive, do you mean it cuts power/response totally? or goes into "limp"?

Hi there,

thanks for the response.

I would say the throttle goes to an idle mode, i.e. when the problem occurs during acceleration the car decelerates, and when at low speed there is no pickup - but the engine doesn't die ( but then I do disengage the clutch pretty quickly and release the accelerator pedal).

I was going to change the brake switch first, but if I left foot brake whilst driving this doesn't cut the accelerator.
I have also read that it could be the clutch (cruise) switch. My car does not have cruise control but the clutch switch is fitted.

Finally previous threads seem to suggest that the symptom only shows when PSM is on, but mine happens whether PSM is on or off.

I feel there must a clue in the above to help me identify the likely problem, before I start to change parts at random.

Again any help or suggestions much appreciated.

Andrew

Andrews, your issue sounds exactly like mine. Change the switches as a cheap (but contortionally frustrating!) attempt to fix it yourself. I actually sold my car last weekend but my problem was cured for the three weeks that I drove it after the switch change.
Good Luck

Hi thanks for the response.

Did you test your old switches when removed to find out which one was the culprit?

I'm tempted not to change the clutch microswitch as I can't imagine this would cause the problem - but that's just a hunch.

Regards

Andrew

I didn't check the switches, truthfully I didn't even think to do that. Interestingly, I had noticed that my cruise control would only intermittently engage/work and just an ever so slight pull OUTWARD on the brake pedal would disconnect it if it were engaged...odd. I just knee jerk changed them all.

Okay thanks for the info, I will keep you posted of what I find when my parts arrive.

Thanks again
Andrew

Update
 

So I decided to change one part at a time to try to find out the cause of the issue starting with the brake switch.

I took the old one off and tested it on the bench - it all seems to work fine, with a definite clean switch from closed to open.

I then installed the new brake switch and have since driven 100+ miles and made 8-10 journeys.

So far no instance of the symptoms I was seeing - which I find surprising.

Given that the old switch seems to work fine on the bench I am wondering if it is either
a) a subtle switch problem not seen on the bench
b) the self adjusting mechanism on the brake switch was misadjusted
c) or I have changed my driving style now that I am conscious of the potential brake switch issue ( maybe I am not riding the brake pedal as much )
d) The problem isn't really solved but is playing with me.

I will put some more miles on the clock and keep you updated.

Regards

Andrew