I have a 2002 996 TT -

when I disconnect the battery, then start and drive - I can floor it and get good boost for a few seconds (might get .7 or .8 BAR), then it limits itself to .4 or .5 BAR. If I get on it again, it won't go back up over .4 or .5 BAR. If I disconnect the battery to reset it, same thing happens. I get one shot at good boost, then it goes back to the .4 or .5 BAR limit.

I filled up with 93oct shell. ran about 1/4 tank down, filled up with exxon 93 oct. same issue continues.

I'm hoping someone on this board can explain what the problem is? PLEASE!

thanks
Brian

 

are these cars really this sensitive to 'gas'?

 

i dont think it is. what mods do you have done?

 

it is stock. it is pulling code p0327, knock sensor bank 1 low voltage. this appears to put it in 'limp mode'.

 

It is definitely going into limp mode...here is what the manual says:
Possible fault cause
♦ Break in wiring or short to ground
♦ Contact corrosion on the connector
♦ Knock sensor loose
♦ Short circuit to B+
♦ Knock sensor
.....Terminal III/49 and III/50
Notes:
♦ When a fault is stored, the ignition angle is retarded for all cylinders
in the range in which knock control is active.
♦ Knock control adaptation is inactive.
♦ If knock control becomes active here, this may indicate engine
damage (increased noise level)

Other questions...check for leaks, how old are the plugs? cracked coil packs....

 

thanks for the feedback!

ok, found the problem! I figured the knock sensor was unplugged or something. So the sensors are BURIED in there. I ended up having to take the it down to removing the alternator, and could barely even see the knock sensor. So, I get it all apart and I see a bird skelton and bunch of crap in there. worked for an hour to dig that out, shop vac it all up, etc.

can't get a hand to the knock sensor - impossible in the car. I put a grab claw on it, and with a really long screwdriver got the connector off. sure enough, the damn bird chewed the wires off!

Reworked the connector, added new wire, etc. got it all back together and now it is working great!

thanks guys.

 

it has 28000 miles - so I assume the plugs are just as old. I guess I should think about changing them now too, right?

 

When the car goes in for the 30,000 mile service, the plugs get changed. I know dealers charge an arm and a leg for that service, mostly because of the labor for the plugs, so if you can change them yourself it would save you some cash.

 

Can you explain further on what you meant by "I ended up having to take the it down to"

I have the same exact problem. Did you just take out the alternator to get to it or did you have to drop the engine a bit?

 

Thanks for follow-up. So many folks post problem and never say how they solved it so others can use search and learn.

 

Great diagnosis Wross!! Glad problem is solved now too.

 

I didnt drop the engine. I took the alternator completely off and the y-inlet pipe off. But that was about it. The knock sensors are located on top of the block, one on each side of the engine. they are almost impossible to get to in the car. remember, all i had to do was work with the knock sensor wiring and only on one side. if you have to remove a knock sensor, i dont think it can be done without more dissassembly. I was on the driver side. I dont know what it takes to get to the passenger side knock sensor.

before you do all this, are you sure you have this problem?

thanks
brian

 

Yep. I'll post up pics later. 3 bags of nest. Nice PPI there Roslyn Heights Porsche. Car had a pending code within 2miles of driving it and the problem was obvious when i started looking into it.

I was able to pull the sensor (same bank as yours (drivers)) with the engine still in the car. the wires were gnawed off pretty bad. i'm going to splice in some new wiring and finish getting the nest remains out of there.

FWIW, i did it the same way you did. Removed the intake plumbing, the alternator and also pulled the rear bumper/heat shields/etc and dropped the engine about 2-3 inches. it's very tight back in there but so long as i can get the bolt started back in the knock sensor, i can complete the job.

Thanks for your post. I knew exactly what to expect!

Donnie.

 

One thing to check into is what sort of wire to use. The voltages that most knock sensors output are minuscule so the wiring is often shielded. I do not know much about the Porsche sensors but on other cars folks have used shielded cables out of USB and network cables to do repairs. The very last thing you want is to find out that stray voltage is leaking into those wires and tricking the ECU into pulling timing. Hopefully the Porsche sensors are built differently than what I'm used to, you may be able to examine a piece of the old wiring to determine if there was anything "special" about it before replacement...

 

Thanks for the heads-up. Looks like standard 22gauge stranded insulated copper, though.