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Having had this issue and having chased it almost as long and hard as Zygrene, I'm placing my bet on the brake/clutch limit switches. A misfire count of 1 is hardly a major indicator. When you have this hesitation problem, you eventually realize that most of the time the engine performs perfectly. When it happens, the engine feels like it's in a coma... no response from the gas pedal or pressing the gas makes the engine bog down further. I eventually realized that the engine control unit was getting a bad signal, and it was holding back the engine from accelerating like the driver was asking. That bad signal is coming from a limit switch that thinks the driver still has his foot on the brake or clutch, when he doesn't. Replace the limit switch and voila - problem solved. Zygrene has the switches. The job is a simple procedure, but a bit of a back breaker in terms of how you have to contort yourself to get under the dash, push the pedal in while pushing the switch into place and rotating 1/4 of a turn. Zygrene can handle it. I expect a good report soon.
Replaced both switches today (wow what a back breaker) and symptoms still exist. Switches didn't seem to help at all. Still getting intermittent hesitation at low rpms and Durametric shows roughness values above 1.5 on cylinders 1/3/5. CEL came on for 1/3/5/6 misfires. I'll probably swap coils around next.
Has anyone done their cam position sensors? Are they easily accessible without dropping the motor?
Having had this issue and having chased it almost as long and hard as Zygrene, I'm placing my bet on the brake/clutch limit switches. A misfire count of 1 is hardly a major indicator. When you have this hesitation problem, you eventually realize that most of the time the engine performs perfectly. When it happens, the engine feels like it's in a coma... no response from the gas pedal or pressing the gas makes the engine bog down further. I eventually realized that the engine control unit was getting a bad signal, and it was holding back the engine from accelerating like the driver was asking. That bad signal is coming from a limit switch that thinks the driver still has his foot on the brake or clutch, when he doesn't. Replace the limit switch and voila - problem solved. Zygrene has the switches. The job is a simple procedure, but a bit of a back breaker in terms of how you have to contort yourself to get under the dash, push the pedal in while pushing the switch into place and rotating 1/4 of a turn. Zygrene can handle it. I expect a good report soon.
Cam position sensors are very easy. With misfires on both banks though, it's unlikely both are failing at exactly the same time.
With misfires on 5 and 6 now, the simply swapping of those coils won't be as revealing as it would have when the misfires were just on 1.3, and 5?
Cam position sensors are very easy. With misfires on both banks though, it's unlikely both are failing at exactly the same time.
With misfires on 5 and 6 now, the simply swapping of those coils won't be as revealing as it would have when the misfires were just on 1.3, and 5?
Agreed. I'm leaning towards having a shop do a leakdown test before I mess with coils or cam sensors. Compression was good but that doesn't paint the whole picture. Still doesn't make sense why the misfire doesn't happen at high rpm.
Replaced both switches today (wow what a back breaker) and symptoms still exist. Switches didn't seem to help at all. Still getting intermittent hesitation at low rpms and Durametric shows roughness values above 1.5 on cylinders 1/3/5. CEL came on for 1/3/5/6 misfires. I'll probably swap coils around next.
I will give you credit Zygrene for chasing this rabbit... I know you are learning a lot about the car, but I would have dropped it off at my local mechanic by now. A good and honest Indy with lots of experience would have diagnosed and possibly solve these issues fairly quickly. Appreciate you sharing your progress and keeping us up on everything you are trying. Hoping for the best resolution soon
Which is the 3rd? I replaced the brake light switch and clutch pedal cruise control cancel switch.
Originally Posted by qikqbn
I will give you credit Zygrene for chasing this rabbit... I know you are learning a lot about the car, but I would have dropped it off at my local mechanic by now. A good and honest Indy with lots of experience would have diagnosed and possibly solve these issues fairly quickly. Appreciate you sharing your progress and keeping us up on everything you are trying. Hoping for the best resolution soon
Doing my best before I shell out $$$$ to an indy! And I'm definitely learning a lot. I don't always want to be dependent on shops but I'm getting very close to calling it quits with this issue.
An acquaintance pointed out that the misfiring cylinders (1/3/5 and sometimes 6) are all in sequential firing order, and may be caused by a faulty crank position sensor. Anyone know the proper method to replace the crank position sensor? I understand the sensor (blue arrow) can only be reached from under the car but what about the connection (yellow arrow)? What do I have to remove to access this from the engine bay?
Which is the 3rd? I replaced the brake light switch and clutch pedal cruise control cancel switch.
Clutch Pedal Cruise Control Cancel Switch (Red/Black) Part #: 996-613-114-01-M100 $23.25 Brake Light Switch at Pedal (Brown/Black) Part #: 996-613-113-02-M100 $23.25
I replaced the first 2 on my car, clearing up my problem. This 3rd switch appears to signal when the clutch is fully depressed, where the other 2 switches indicate when those pedals are not depressed. Clutch Pedal Ignition Lock Switch Part #: 997-613-109-50-M100 $39.25
Guys - I've decided to bring the car to BRracing in Los Gatos later this week. Getting all sorts of suggestions from Rennlist, Youtube, IG, etc (all are MUCH appreciated) and it's turning into more of a headache to self-diagnose than it's worth. Let's hope BR is able to solve this quickly! I'll keep you all posted. Should have an update by Friday afternoon.
Guys - I've decided to bring the car to BRracing in Los Gatos later this week. Getting all sorts of suggestions from Rennlist, Youtube, IG, etc (all are MUCH appreciated) and it's turning into more of a headache to self-diagnose than it's worth. Let's hope BR is able to solve this quickly! I'll keep you all posted. Should have an update by Friday afternoon.
I think that's a good decision. I've read people dumping thousands trying to resolve these kinds of issues with no luck, then ending up going to an indy/dealer.
I'm interested to see what they find. Good luck
I think that is the best call for now. I have learned in life and career that if I can not easily solve a problem within a certain amount of time, then it is best to call in a professional with lots of experience. Although it was good to swap out some of those old parts and lots of the suggestions have good merit, it is still money spent that did not solve the problem or have the desired effect. Time to have a pro take a look. Keep us posted and best of luck. Hoping it is something simple and not too expensive.
If anyone is curious - here's a video on my Cayman S ownership experience and why I sold it for the Carrera, along with an explanation of the misfire issue and everything I've done to diagnose:
To recap my earlier post I've been having a "dead gas pedal" hesitation problem for about three weeks. I'll be driving along, usually around 3000 RPM or so, and the gas pedal goes dead. If I take my foot off the gas, it resets and goes again. The problem is intermittent but I usually get at least one or two events of dead pedal hesitation every time I drive my 997.1, and sometimes I'll get a lot more than that. Very annoying.
After reading TV911's posts about how he solved a similar problem by changing out two electrical switches at the brake and clutch pedals, I thought I would try that. I ordered the two switches at Pelican Parts for $26.75 each. This morning I installed them. I got the old switches out very easily, but installing the new ones was quite a bit more challenging. There isn't a lot of room to move about in the driver's footwell under the steering wheel, and it is challenging to get the switches pushed in and twisted a quarter turn at the same time. The clutch switch was difficult and the brake switch was really difficult due to the ventilation air duct being in the way of the switch. With some persistence and body contortion I was eventually able to get them installed. For the brake switch I was finally successful by kneeling on the ground outside the car and using my right hand to press the switch into its fitting and turn at the same time.
After I got the switches installed I took my 997 for a nice long drive on residential streets with many stop signs, and the problem is gone. I'm sure that I've solved the problem with changing out these two parts. Also, my engine seems to be running smoother too. I will report back in a week or so. If I haven't had any dead gas pedal events in a week then I will feel very confident that changing out these two parts was the solution to the problem.
The part numbers for the parts I changed out are:
Brake light switch at pedal: (Brown/Black) 996-613-113-02-M100
Clutch pedal cruise control cancel switch: (Red/Black): 996-613-114-01-M100
@Zygrene, I know your problem is a bit different from mine but maybe this will work for you too.
Thanks very much to @TV911 for providing the information on this fix.
@tinroof - glad the new switches solved your issue. Unfortunately they didn't work for me.
BRracing performed a smoke test and found vacuum leaks at the intake couplers (I just replaced these - argh!) and AOS vent line. Looks like whoever replaced the AOS 1-2 years ago didn't install it properly. BRracing also pulled the codes and found misfires on cylinders 1/2/3. First time I've seen only bank 1 show misfires. Usually I see 1/3/5/6. I authorized the shop to fix the vacuum leaks and install the 996 Motorsport AOS that I previously bought and didn't install. Going to be 6 hours of labor at $195/hr, plus the 1 hour for diagnostics. Hopefully no additional charges. There's no guarantee this will solve the misfiring but I can't think of what else it could be. Vacuum leak sounds like it SHOULD be the source of misfiring across both banks, but the fact that only bank 1 is misfiring right now is a little strange...
11-29-2020 | 05:14 PM
