Captsteve123

It has not done this in a while. I only drive on sport mode, and it never does it.
Dealership could not find any problem with the car. I probably should drive it without sport mode on and see if it does it again.

fourplates

Good point. Mine has not done it in sport mode, but I don't typically switch it on until the engine is warm. I'll try that.

And just to repost my issue so perhaps someone with experience in this area could assist:

2005 C2 w/ sport chrono - 51k miles

No error codes that I can read through DashCommand and the GoPoint BT1.

Symptom summary:

- When the engine is cold sometimes a big lurch accelerating out of 1st at stop signs or otherwise. Happens more often when my car is angled down.
- Some hesitation in the 2500 rpm range, I believe this happens even when warm so it may have to do with ECU controlling the throttle
- Very bad gas mileage in town
- Misfire readings on Cylinders 1 & 6 when I bought the car (Fire order being 1-6-2-4-3-5, cam timing chains do the most *work* from 1->6 if I understand it correctly)
- Rough idle, engine drops under 1k rpm after cold start almost immediately (instead of ~1200 rpm for 5 seconds as most other owners report)
- Typical mechanical sound on tickover that increases in frequency as RPM climbs (a little louder from driver's side engine bank) <-- likely nothing to worry about
- A few weeks ago over a span of a few days, engine would fire a few times then fail to start with an "oil pressure warning" light. After starting a 2nd time it would run fine... this hasn't happened since but could be related.

Ideas:

- Throttle control + MAF may need cleaning/replacement
- Perhaps a leaky gasket around throttle body
- Brake switch is faulty (brake being reported to ECU as engaged even when not engaged, causing ECU throttle manipulation)
- Issue with fuel injector / valve, using "techron" suggested (no experience using additives)
- Spark plugs / coils (plugs were changed at 40k)
- Symptoms reported as fixed by user with worn clutch that needed a new flywheel. I am likely going to replace my IMSB when this work is done.
- Fuel purge valve not working properly

I have searched extensively and found users that have had similar symptoms. Anyone have thoughts on the above issues?

Gonzo911

I had a similar problem in my 996. At first I thought it was a bad clutch (only 5k miles on a new clutch). Then, after posting about the problem on RL, several members who had the same problem noted it sounded like a bad clutch pressure plate or the clutch disc was installed backwards. Took it to my Indy and it turned out to be a bad clutch sensor switch. $22 part that when it fails, mimics a slipping clutch (usually from first great only). First time most of us had ever heard of the darn thing. I would assume the 997 has the same switch.

We all wondered how many $2,000 clutch jobs only needed a $22 part.

997_rich

If you're not throwing codes I think you can probably rule out misfires and coils/plugs. I think you can rule out clutch by your RPMs matching speed.

I think I'd look closely at:

• Sticky throttle plate.. remove the rubber boot and verify that it's not sticking (or throttle plate actuator).
• aftermarket intake? if so, remove it.
• Doublecheck battery to make sure that the battery voltage is not dropping below ~13v during these events
• take off serpentine belt and verify all pulleys can be turned by hand (except the crank pulley).
• put a gauge on the fuel rail and verify fuel pressure. I've seen cars act this way when the fuel pressure regulator valve is stuck open.
• maybe consider taking the car to a dealer or indie to pull the codes. It's very surprising that the car is acting like this an not throwing any codes.

fourplates

Thanks for the tips! I'll report back when the issue is resolved.

danit

Do the folks with this issue have a manual? I remember this thread from Planet9. http://www.planet-9.com/987-cayman-b...eated-joy.html

Could this be your issue or at least maybe it is over reactive?

fourplates

I have had my switch taped down all day with electrical tape. The lurch didn't happen on either of my two cold starts today. "Feeling" the switch action it seemed like it could be defective. It's a cheap part. I'll order another one.

Thanks for pointing that out Danit.

kellen

Any update? Having same issues of a drop in rpms after take off. Only recent changes are a battery exchange and eval of starter that wasn't replaced.

Turboslut

assuming it is this switch:

996-613-114-01