theiceman

I hate to sound like one of those " i have a friend" guys but ...
I have a friend who is to cheap to have internet but owns a Porsche.. okay now that is out of the way ...
he says it starts fine but as soon as he get above 50mph it starts bucking and lurching ,, it even left him stalled out at the side of the road and he couldn't restart it . he got it towed home and when cold it starts fine againa nd he can drive it around as loing as he stay below 50mph. I have never heard this one come up before .
Sounds to me like a fuel pump. I don't think the DME relay could casue this could it ? i suggested he get one anyway and even if it doesn't fix it he has a spare. I have heard of the CHT sensor causing simialr issues however. Any ideas from the Carrera crew > if it were CIS I would have walked over and fixed it by now but i don't get these new fangled computer run cars

Ed Hughes

First, some background info:

Does he have funny-looking wheels?

That does seem like it may be something to do with fuel. Or, maybe a vacuum issue in the manifold connections? The DME would be the logical starting place, but I'd not think that would be speed related.

Is he sure it isn't RPM related?

rusnak

It's really easy to check fuel pressure and delivery on the 3.2, much more so than on a CIS equipped 911. The ball check valve is on the left side fuel runner.

It sounds like it COULD be a DME problem. Sometimes the brain has a cracked solder joint. I'd probably check the vacuum line to the fuel pressure regulator, and make sure the o2 sensor is working, Ohm out the sensors, etc all the common sense stuff that is easy to do.

BTW I have friends who are too cheap to have their cars fixed properly, so they call me to help. It's not bad, it is what it is.

ricster

No Internet????? WTF ok. So to me it sounds like a fuel pressure problem. I would check fuel pressures under load. Could be something as a blocked fuel filter.

theiceman

Yeah can you belive the guy no internet . sheesh .. ! wants me to go over and look at it , he doesn't want to spend a lot on a mechanic. i think he is going to get a Bentley and at least we have a starting point. I am not sure if it is DME related ed . I am going o go over this week or next and have a look. don't know the layout that well though .. I should be able to tell when I take a look. doesn't sound DME to me but you never know .. I want to check his CHt sensor.

User 4221

Is it road speed related or RPM related?

Can he change gears while maintaining speed and make the symptoms change?

Could the VR be dead and the DME responding?

theiceman

i will have a wander over later this week or next and have a look ,,

rockrimmon

The Bentley comment fooled me. I though: "Wow, too cheap for internet, has a Porsche 911, and now is moving to a Bentley". Then recalled you probably meant the service manual. :-)

Tom

MUSSBERGER

No good deed goes unpunished

theiceman

yeah I hear ya .. i am interested in learning about the Carreras a bit more anyway ... figure i would get a look at the fabled DME relay and make sure the CHT sensor is actually plugged in. ( if I find it ) admitedly I can't do much about a bentley. You never know I might find a busted cap and rotor..anyone know if it the same as the SC ? I have "good spares" of those I could throw on for troubleshooting. and if the coil is the same I could put mine on his car to see what happens.

whalebird

Road speed or engine speed? that will help a bunch. Be careful Ice...

SPDADCT

When was the last time he got the car tuned (Spark Plugs, Fuel Filter, etc)?

whalebird

Some failure modes are load-dependent, especially ignition.

theiceman

not sure about the maintanance as he has only had it for about a year. But he said it was running perfectly then out of the blue it started doing this. I think we are going o find it is RPM dependant under load . I am suspecting we will be able to rev it in the driveway but not under load. I will report back when I have more details.
actually Ed it doesn't have funny wheels so that can't be the issue it is a blue coupe the 7 and 9 Fuchs.
I have learned since it is an SC with a 3.2 in it .. see what happens when you put a 3.2 into a nice solid SC

whalebird

I would choose a 911 over the interweb anyday. Even if it was one of those valve-guide eating 3.2s bolted to that grenade of a 915.