[madridcab]

Had the injectors cleaned and balanced and the slight hesitation on pick up when cold has disappeared, the car now is very smooth, although still really "kicks" only from 4000 up, acceleration is not totally linear, but feels like it has a couple of "steps" on the way, is this normal?

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

Hesistation on acceleration can be caused by many things. Start with a blink test, and go from there. I had a severe hesitation problem a few years ago, and in my case, it turned out to be bad plug wires. At least yours doesn't sound like it's too severe, but it really should be completely linear, with no "steps" along the way. Good luck.

Partial Post: Please Login or Register to read the full post.

[PorscheDude]

Have you changed the fuel filter lately?



Also try cleaning the MAF sensor.

Partial Post: Please Login or Register to read the full post.

[Anchorman]

I also find there's extra "ooomph" once you pass through 4k rpm or so.

Partial Post: Please Login or Register to read the full post.

[Darryl]

The extra "ooomph" is the variocam, no?

Partial Post: Please Login or Register to read the full post.

[PorscheDude]

No, it is the intake manifold.



Darryl, thanks for the parts.

I owe you..... <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />

Partial Post: Please Login or Register to read the full post.

[S_Cal968]

The powerband is fairly flat - my car seems to pull until I hit the rev-limiter. If I recall, dyno runs typically show a slight blip where the variocam transitions, the torque peaks at ~4500rpm and the hp peaks at ~ 6800.

Partial Post: Please Login or Register to read the full post.

[xrad]

madridcab: I have the same hesitation and a good kick at about 4000, too. Almost feels like boost coming on. This is a new problem , and the car is running rich.



Did you find out what your problem is????

Partial Post: Please Login or Register to read the full post.

[PorscheDude]

IIRC @ 4200 the intake produces 3 to 4 psi of boost.

Partial Post: Please Login or Register to read the full post.

[flash]

correct - at about 4200, the dual resonant intake manifold is acting a bit like a turbo - the porsche sales literature specs the "boost" at .3bar or 4psi



the variocam kicks in at 1500 and out at 5000

Partial Post: Please Login or Register to read the full post.

[Lonestar968]

Madrid, I had a wierd kind of surging/stepping of power a couple of years ago, very much like what you described. My mech discovered that the cannon plug for the VarioCam (in the vicinity of the intake manifold) had become very brittle and cracked allowing a sporadic "signal" to the VarioCam. He replaced the pigtail and it was fixed!!!



Hope this helps.

Partial Post: Please Login or Register to read the full post.

[rhudeboye]

Sounds like a few happy new 968 owners with all this vario talk.

Well for those that don't know, swap your chip with the RSB and you will feel the punch earlier then 4K. However I don't speak from experience. I own the chip but have yet to install it.



Enjoy your post 4k runs.

David

Partial Post: Please Login or Register to read the full post.

[madridcab]

I may not have been clear enough on my original post, the car is actually now running great (before cleaning the injectors I had hesitation on acceleration, but no more), but it is really "kicking in" a bit above 4K, and from what I see this is quite normal due to the intake manifold.. (BTW my old 964 also had a bit of this behaviour, whereas the 993 is more "flat"), I will play with the varioram, but suspect it is working OK. What I have seen on several threads, though, is that aftermarket chips tend to even out the torque curve, so perhaps this is the way to go. As a general comment to people with hesitation problems, try professional injector cleaning, dirty injectors will cause hesitation. Fuel additives will likely not have much effect, and based on my experience is a waste of money..

Partial Post: Please Login or Register to read the full post.

[PorscheDude]

IMHO, there is no cure in a can.

Partial Post: Please Login or Register to read the full post.

[flash]

while i am certainly not a big believer in "wonder goos", Run-Rite does seem to work well, and is especially effective if you go to one of their service centers and have them clean the intake - i wouldn't have believed it if i hadn't seen it myself on multiple cars

Partial Post: Please Login or Register to read the full post.

[kwikt]

What about the fuel injector cleaning process that hooks to the fuel rail and is used with a chemical and compressed air. Reason I ask is because my friend works for one of these companies and swears it works. He's suppose to do it to my car this weekend. Just wondering if he's waisting his time. The car has 115,000 miles on the clock.



Kevin

Partial Post: Please Login or Register to read the full post.

[flash]

never tried that one - the Run-Rite treatment hooks up to a vacuum port on the intake manifold, and is pulled through the intake - there is also a manual cleaning step using a brush tool

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

[quote name='smokiemon968' post='59462' date='Sep 10 2008, 09:15 AM']IMHO, there is no cure in a can.[/quote]

I've had the same experience. I also tried Run-Rite on our 2003 Chrysler Minivan, which I thought would be a worst-case test because it gets driven on so many short, gunk-building trips, but I didn't notice improvement in power, smoothness, and certainly not in gas mileage. The shop said not a whole lot of smoke came out of it, either. Yet many have sworn by Run-Rite, so I'm not sure why my experience was such a dud.

Partial Post: Please Login or Register to read the full post.

[flash]

well, there is a difference between the results of just dumping in the bottle, and actually having the intake cleaned - which did you have done?



i have personally seen the full treatment done on 5 968s - every one of them got better, in varying degrees - never done the bottle alone, but i understand it is nowhere near the results of the full treatment

Partial Post: Please Login or Register to read the full post.

[94SilverCab]

Not only did it on my 968 but also my 1990 Miata and my wife's 1998 Explorer..my experience with each was that it ran objectively better...lower RPMs at idle and definately smoother. Subjectively, I think gas mileage got a little better...not enough to be remarkable.



Jay

Partial Post: Please Login or Register to read the full post.