996 3.6 Revving itself

[KCB_96]

Hi there,

First post and new to Porsche ownership, though I've encountered an odd issue recently with my 2002 996 3.6 Targa.

On a warm start, the car is incredibly laboured to crank (which I've tracked down to likely being a Y-cable issue, so that's not too much of an issue.)

However, yesterday I started it when it was warm, and after fighting me with the slow crank, it eventually fired and then proceeded to idle incredibly high (around 1500) I limped it home with no misfires and no CEL or warnings, but the throttle was surging at low revs, the idle never came down from its high point and (most concerningly) the car was revving itself.

My foot was nowhere near the accelerator, but with the clutch in the car would blip the throttle continuously all by its own accord, making me look like some ASBO at a car meet trying to show off.

Having shut down the car and left it to cool completely, I re-started the car but the issue persisted.

I've since carried out a throttle body re-calibration and that seems to have removed 90% of the symptoms (the idle is still a little rough, but it's booked to have a full major service in a couple of days including new coil packs) but I was wondering if anyone had any ideas as to what would cause the car to rev itself?

Additional info: No change in oil pressure or fluctuation, voltage stable, car was fine when being driven other than some slight surging, no CEL, no misfire.

I'll give the throttle body a visual inspection and clean tomorrow, but does anyone have any other ideas?


Thanks!

 

[KCB_96]

Also, since pictures are part of the law around here...

 

[deMort]

Sounds like an air leak on the inlet manifold .. smoke test would confirm which your garage will easily be able to do.

Basically a fueling issue .

Part of a service is also checking fault codes .. if they look at the fuel adaptations that will also point to a possible issue .

Just mention this when dropping off the car and they will investigate it for you .

 

[KCB_96]

Sounds like an air leak on the inlet manifold .. smoke test would confirm which your garage will easily be able to do.

Basically a fueling issue .

Part of a service is also checking fault codes .. if they look at the fuel adaptations that will also point to a possible issue .

Just mention this when dropping off the car and they will investigate it for you .

Thanks deMort - I suspect it's some kind of fuelling issue like you say. If it were a leak on the inlet manifold, surely it would behave erratically all the time when it gets up to temperature?

This only seems to be a by-product of the struggled start; During normal driving it's absolutely fine even when up to temperature, the gremlins only occur after a laboured start when the car is already hot...

For example, the same thing happened after a 2.5-hour motorway run, quick 5 min pit stop and then back out to the vehicle to find it behaving the same... let it cool for an hour and it was hunky-dory again! Bizzarre...

 

[deMort]

As with any fault there are often many reasons that it can be .

Most running faults are far worse on idle than at higher rpm .. i look at the fuel adaptations for all the rev ranges but mainly at Rkat which is fueling at idle .. this is a good indicator of whether the car is over or under fueling.

If you had an earlier model then there is an idle stabiliser fitted , your model is E throttle so not applicable .

You have the possibility that the current draw on starting is on the large side shall we say .. this has the effect of a flat battery effect on the dme .. it would in turn loose its throttle stop limits .. that would affect start only though and would soon be re learnt when driving so the fault would clear pretty quick .

A fault code read out , a look at the fuel adaptations and then possibly a smoke test is where i would start .. Which is what the garage will be doing along with sorting the slow crank issue i suspect


EDIT ..

Post here about the Targa roof including stopping squeaks / rattles etc .

http://911uk.com/viewtopic.php?t=116450


Welcome to Porsche ownership as well :thumb: :bye:

 

[KCB_96]

Hi deMort,

Thanks for all your help - the good news is after having a new battery fitted today, the problems appear to be solved! Turns out that the battery that was in there had two or three dead cells, which explains a lot.

Regardless, I have the car booked in with the same Indy (Northway) to fit a new Y-Cable as a preventative measure, as it's one of those "not if, when" sort of jobs!

Appreciate the link to the Targa top bit too, I've already Gummy'd the rubbers but I'll take a deeper look.

Cheers!

 

[deMort]

Excellent news .. i'm afraid with battery / charging issues then it can cause so many different issues it's impossible to say if its an issue or not ... not a job i like trying to diagnose and i have 2 on the go atm .. sigh .

Northway have a good rep .. i recommend them as well .

Roof noises then have a look and feel free to ask me any questions you like .. i've just finished my 53rd roof refurb today

3 more booked in over the next month .. been a strange year as i normally do 2-3 per year .. done 6 so far this year .

All i can say is use it regularly and never lubricate it .