FLAT SPOT on my 996

[Guest]

I seem to be getting this "flat spot" btw 5200 and 5800rpm. Everything is find below and above this range. I bought the car 7 months ago and put it through its 48k service in June. I am not sure if the flat spot has been there since purchase as I hardly ever get to that kind of rev. But since first discovering it, I seem to make a habit of finding it.

Does anyone else have any experience of flat spot on the 996 (1999 CAB)? Any suggested remedies before a trip to the OPC.......or is this normal

 

[Grant]

Can't say I have ever noticed a flat spot in the 996's rev range, only the usual "jerky" take up at light throttle opening.
Have you had an after market air box (or chip) put on it, as I have heard about certain models causing flat spots in the rev range.
If not, I think it's OPC here we come, best of luck.

 

[tim court]

I have a slight flat spot when pulling away in first. if you pull away gently it sometimes dies and stalls. Most embarassing...[] Reasonable amount of revs and no problems.

Since I fitted an induction kit it has also got a little bit of a lag at about 3500-4000 rpm but as my right foot is usually clamped to the loud pedal it only lasts about a tenth of a nanosecond.

 

[Guest]

I experienced no flat spot on my 2000 model Carerra 4 and am not aware that the 996 suffers such a problem. The OPC beckons!

 

[Tony Daniel]

I've had a similar problem with my Boxster, which to has also done 48,000 miles. It sometimes feels like the rev limiter is kicking in early.
At the last service I was told a part of the HT leads was cracking (I think they called them spark packs, ie ignition coils). They cost about £28 a piece (with club discount) and there is one per cylinder. Anyway the problem is getting worse so I am ordering a set this week, I'll let you know if it cures the missfire.

 

[gaxor]

Don't know if its relevant, but my previous car a 993 experienced a similar problem at around 50K miles. Turned out to be a sensor on the flywheel. It tells the ecu that the engine is running or something, and was turning off the fuel. Very disconcerting when overtaking on asingle carriageway in France!!

 

[Guest]

Thanks for all the suggestions. Took it to the OPC and it turned out to be the Hot air MAF sensor. Technician did not pick up any fault on the test drive but the laptop provided the diagnosis. Apparently, this tend to "go" after about 4 years (ideal timing as most cars would have just run out of warranty). £500 lighter in my wallet and everything is now fine. Part alone was £280+vat...ouch!

Just out of interest, why do technicians have to test drive your car BEFORE pluggin in the diagnostic computer? Surely, the test drive should be deployed if nothing appears on the computer. I just don't enjoy the "abuse" your engine face in the hands of these technicians, particularly when you are sat in the passenger side!

 

[Tony Daniel]

Hot air MAF sensor

I think a MAF sensor is the Mass Air Flow meter, on the induction side (cold air). Porscheshop sell these for £146.80.

They seem to be a common problem on cars at around 4years old.

My car is still running like a dog, I replaced the coils(£181) and it's made no difference []. So I'm having my Mass sensor and the rest of the car checked over next week ££££££££££££££[]