acao

2006 997 3.6
60k
No engine mods
Frequent DEs
Car maintained to schedule or better.

From the time I bought this car in 2008 (20k miles), it's been vexed with a hesitation or lurch when moving from a stop, in 1st gear and sometimes again in 2nd. When starting from a standstill, the car would be begin rolling and for a brief moment, throttle did nothing and then "WHAM," more forward thrust. It was impossible to be smooth from a stop without slipping a lot of clutch to get into high RPMs (where this problem doesn't seem to exist). I don't use alot of clutch, I'm a "just barely enough clutch" type of driver. I just learned to drive around it, and thought it might be some excess driveline lash that would eventually reveal itself someday. Many people have reported a similar problem here, search term "hesitation."

It was worse with a cold engine, but still present when warm. There was no threat of stalling, no weird RPM behavior, no clutch slippage or problems, no bad engine mounts. MAF was always clean, old plugs came out clean at 4 years, and everything else tip top.

Yesterday, I celebrated 60k by having the serpentine belt changed, and all the pulleys. My pulleys were grooved, and have been for at least 3 years, when my mechanic first pointed it out to me. I didn't have the work done then because it wasn't pressing. Edgy has a good thread about grooved pulleys here, search term "pulley."

So far, it seems the hesitation/lurch is gone. Was the hesitation related to belt slippage or a pulley not freewheelng? I've never had belt squeal.

I've only had two drives (my round trip daily commute), but we'll see if this improvement is real or placebo.

Edgy01

Can you better describe your lurching symptoms? Are you seeing the occasional issues that seem to be manifested in the 997.1 engines perhaps due to a sticking throttle plate? (We still don't know the reasons for that).

acao

Sticking throttle plate occurred to me because that's what it feels like. To analogize, my car felt like a water hose, and starting at low RPM felt like someone had pinched the hose while another cranked the spigot **** open: nothing, nothing, and then someone let out the kink and WHOOSH. At a DE, an instructor thought I was being abrupt on the throttle until he drove it himself. My choices were to either use alot of clutch to buffer the surge or be ready to ease up when the power unkinked.

Back to the sticking throttle plate, I'm vigilant about my maintenance. Every year I change the engine filter (I roll <8k miles per year), and while it's out, I make sure the throttle body is clean and moves well. So at least mechanically, there should be no problem. If it's software, I'm not a programmer.

I had a 2003 986 without this characteristic. It had wonky Litronics instead.

As an update, the behavior isn't eliminated, but it is greatly reduced. To quantify a qualitative observation, I'd say it was reduced 75%.

I don't hold my testimonial data set of 1 to be scientific. It could be placebo, it could be attributable to the seasonal rise in ambient temperature, it could be the high grade brake fluid flush (from blue to SRF) which improved the clutch pressure action (though it previously never acted differently with fresh fluid).

Even if it's all bunk, I'd still have every pulley changed with a belt change. And given the change interval, the major pain associated with the tensioner pulley, and the increasing demands on my time, having my mechanic do it was worth the money.

I derive great satisfaction from doing my own work, but my life is alot less receptive to the inevitable, "What's the nearest 24hour auto parts store?" or "I wonder if Suncoast/Pelican ships on Saturday?" For some jobs, the specialized tool will never amortize.

997_rich

what's actually happening with the engine RPMS? do the RPMS climb normally when stepping on the gas?

Is this a better characterization: you're adding RPMS with your right foot, you take your foot off the clutch with no grip and then, wham, the clutch grabs after your left foot is already completely off the clutch? it sounds almost like your clutch is slipping and then grabbing.

what happens with the RPMs when you lurch? does it suddenly jump up (like the engine finally got the fuel it needed) or does it suddenly drop (like it was revving fine and the clutch finally gripped and took the engine power to move the car forward).

Zeus993

Now that you've posted this, I do have a similar situation. It happens when I drive, errr... normally. It strikes me that 'something' is stiff and reluctant to 'open'. If I drive it aggressively it's not problem. Someone mentioned that the car will 'set' the throttle response based on the drivers style. Thoughts anyone? ACAO - have taken it out for a really spirited run to 'reset the throttle response' and checked the hesitation after that?

acao

During the lurch, engine RPMs match wheel speed, not throttle input. So, in the lurch, RPMs are depressed.

acao

I do DE about 7-10 weekends a year. So yes, it has plenty of spirited runs.

Captsteve123

I know this thread is 2012, but I am experiencing this same issue. It hesitates in 1st gear and on some occasions the same thing in 2nd gear. It almost acts as if the car is going to stall, much like the old days when cars would get vapor lock.
Very hard to duplicate it, but it does it on its own, and you never know when it will happen.
2005 Carrera.

USMC_DS1

A new clutch @ 60K miles resolve this issue for me. I had grown used to it and had adjusted my clutch play accordingly. My SA noticed it and recommended a clutch replacement. He also noted that the clutch was stiff... again, something I had grown accustom towards and didn't recognize. Have a good tech test drive your car... I take my tech out to lunch once a month and have him drive the car. He tends to discover anomalies which I've grown used to and deal with as a charming characteristic of the car.

Captsteve123

Thanks for that feedback. I am actually taking the car in to replace the IMS bearing, so having the clutch done at the same time will be my action plan. My Vin # falls in the class action lawsuit, so I better get it done as a preventative measure and piece of mind.
Thanks again!

Captsteve123

Well it happened again. This time I was getting on the gas in first gear, at 4000 RPM's, it lost power as if I was n the brakes, then cleared out going into 2nd gear. Not sure what is going on.
Taking it tomorrow to get the IMS bearing and clutch replaced.

Any other possibilities of this cause?

Macster

Let's see...

No CEL so misfires or other engine or sensor malfunctions are not occurring. E-gas probably working ok.

What does that leave? Well, one thing that comes to mind is an intermittent fuel pump issue or a fuel line with a crack/split in it that under some conditions opens up and bleeds away fuel pressure.

USMC_DS1

What was the weather like at the time this occurred? Rainy by chance?

Captsteve123

Weather was dry, no rain and about 80 degrees.

I hooked up my durametric software, and checked entire car, and systems, and had no codes. Checked out fine.

How do you fine out if it is the fuel pump, or hose? Never had any smell of fuel fumes.

fourplates

Hi Capsteve, did you ever get this resolved?

My car (2005 C2) does this occasionally when cold. I think it may be the clutch (still on the original) or the MAF/throttle body.