springer3

You may need to get back to basics. The exotic stuff needs to be checked, but pre requesites for any spark-ignition engine to run properly are:

Compression: Have you checked it? What are the values?

Ignition: Are both systems firing? Are the plugs, caps and wires clean and in good shape? Is the timing advancing as it should? Sluggish at high RPM could be the timing advance.

Fuel: Check the cleanliness and delivery pressure. If your octane is too low, the DME will limit the timing advance to compensate, and that will make the car sluggish.

If all else fails, get to a shop that can read the diagnostic codes. You could be in "limp home" mode, where the DME has detected a fault, and limits power to prevent engine damage.

Cupcar#12

a couple of questions.
when was the last time you changed

1. the fuel filter
2. the O2 Sensor
3. checked timing
4. check disti belt
5. read the fault codes
6. Checked the o2 sensor wiring (it can melt in certian cases, shorting the 02 sensor - had that happen)
7. Checked the cat (they get plugged and create excessive back pressure)
(some of these have been repeated above)
- Without a hammer it is replace and pray diagonostics unforunitutally.
8. Checked the DME

If nothing is happening over 4K Rpm then the root cause is most likely one of these not the DME - the DME registering a fault and limiting timing, etc to protect the motor.

Just a thought or two

Indycam

"7. Checked the cat (they get plugged and create excessive back pressure) "

Thats what I've just been fixing , the last section came loose and got pressed into a plug shape that
bunged the exhaust .

Marc Shaw

No offence intended but have you driven any other 964's and know what they are "supposed" to feel like? Is it different than when you first got it or are your expectations just not being met? It feels weak compared to what - what it used to feel like, like someone elses', or what you think it should feel like?

I only ask as a lot of people here are trying very hard to help you fix a rather vague sounding problem - more info might help

Marc
p.s. Happy birthday.

JasonAndreas

Mike,
You might also want to temporarily run with the original chip (just to see what happens). Winter gas reformulations just came out within the past two weeks so it is possible that the DME control unit has pulled backed the timing because your "cup" chip had advanced it too much (i thought cupcar chips required 98-100 octane?) The gas thing is just a wild guess but usually the first thing to do when you have a running problem is to go back to the original chip (unless you have a MAF).

H964

o2 sensor new
cat bypass
all wires and coils are perfect
cars runs on either distibutor super smooth
fuel filter new
problem existed before installing chip (chip works great)
no check engine light
i hear the resonance flap engage
cleaned isv and afm
wot get engaged at full throttle

have not checked fuel pressure
have not checked knock sensors
have no checkked engine compression
will test the at the dme sunday
no , i have never driven another 964, but i drove a 3.2 the other day, and i can tell you that it feels stronger up there
i was recommended to this very good shop, so monday i will have an answer i hope!!
by the way, the other day i down shiffted from 4 to third like a i always do, and the car just blew me away it felt like never before, so i think my problem is more electrical , some stupid wire or sensor acting up, but its a pita to find
hope you guys have a great weekend

H964

by the way,I think the idle speed contact and full load contact connector (throttle valve switch) diagram is labeled incorrectly in the workshop manuals and adrians book . It should be 1-2-3 but instead its drawn 3-1-2. can someone comment on that ????

Dunasso

I'm Done, sorry I couldn't help. Seems like we covered every possibility and now the problem has been temporarily resolved. You must have a loose wire or connector somewhere.
Good luck at the shop, let us know what happens.

Duncan

robbed666

Hi
As the the connector is a flat 3 way type the wires going into the back of the loom side connector should just visable before the black outer insulation. Brown is ground (pin 2), white with brown tracer (pin1) is idle switch wire, and green with yellow tracer (pin 3) is the WOT line.

HTH

P.s According to the diagram there are no intermediate connectors, i.e the wires from the engine compartment 3 way connector go straight to the ECU.

H964

iam starting to believe that i have a fuel problem. i only get about 180 miles for a full tank of gas.
can a low fuel pressure cause that????
o2 sensor is new

Marc Shaw

Ouch! That is not good mileage.

180 miles = 290 km

I'm getting about 400 - 450 km/tank (250 - 280 miles/tank), depending on city versus highway so something is funny about your gas mileage.

Marc

dougn

check the fuel pressure

Cupcar#12

180 miles per 16 gallons = 11.25 mpg (16 gallon tank) probably less since you typically fill up when the light comes on.
Super rich mixture then.
you just changed the O2 sensor - right? OEM? or off the shelf bosch? (it is a 2 wire sensor so the off the shelf ones will work) is it wired right?
it might be reversed...
fault codes would be helpful - kinda hard diagnosing without that info

Adrian

Based on the fuel consumption figures this 964 is running in open loop mode at all times. The cause of this could be the bypass pipe itself. If there is an incorrect gas flow, then the O2 sensor will not work properly and the DME will never use its input keeping the system in open loop mode.
Running in open loop mode all the time will remove the "kick" felt at around 4000rpm because this is when the DME switches from closed loop mode to open loop mode.
The best way to check that the system is working is to reinstall the catalytic converter.
I would also advise following the suggestion from Rob, which is to check the type and part number of O2 sensor fitted.
The 964 requires a specific Porsche part number and substitution with a "cheaper version" is not advised.
Ciao,
Adrian.