captek

Hi guys I need help with a 1990 964 C2 Coupe.I rebuilt the engine with all new pistons etc.Car does not leak a drop runs really good,but here is the problem,at idle the car runs perfect but starts to hesitate when I mash the throttle only after it warms up.When I had the engine out I put in a new head temp sensor.I checked the fuel press and was loosing pressure after you shut down the engine,I changed the reg and fuel press is good now.The car used to be hard to start when it was hot.That problem cured.But the hesitation problem is still there,the weird thing is when I drive the car it runs good with no hesitation.Its only when the car is stationary.I know this is not right.I do not pull up any codes at all.I,am using durametric software,and I checked the software by disconecting the o2 wire and it came as a code so I know the software works.The coils are both new also the coil wires.I happen to have a new AFL sitting around and switched it and still the same problem.The ox sensor is new.The idle speed valve is good.I tried a new relay still the same thing.I did try to put a jumper wire the 7 and 3 termial and the car would not start.I am completey at empty at this point I do not know what it could be any suggestions would be greatly appreciated.Captek

ilko

When you disconnected the O2 sensor, did you still experience the hesitation? Sometimes a bad O2 sensor will not throw a code.

captek

Yes it was the same,Ive tried everthing and I am at aloss.Thanks for the help.

Richard Curtis

Check that all vacuum lines are good. A leaking vacuum line can cause driveability problems. On cars this old, it might be wise to replace all the vacuum lines anyhow.

dfinnegan

Is your idle switch working correctly?

captek

Hi yes I check it ok.Its strange the car runs so well at idle pulls upno codes and it doesnt hesitate when driving just at a stop. I have checked and rechecked everything I,am at a loss.

dougn

your issue sounds like mine. i describe it as poor throttle response. at idle when you stab the throttle it takes too much time to respond right?

Mark Brook

I had the same problem for about 18 months. Turned out to be a bad connection on the AFM. Runs like a dream now, so well worth checking.

Cheers,

Mark 90C2.

captek

Hi thats exactly how mine runs takes too long to respond.Checked the connector to the AFM looks good.Mine only does it when it is warm and i have a new temp sensor in the car.

dougn

yeah mine gets progressively worse the warmer it is. it's really snappy when cold.

captek

Thats just like mine.Anybody have any ideas.

911addict

Too much fuel?
I know the turbo is different technology, but after my service the garage set it slightly richer than before (but still within Porsche recommendations) and it felt like a very heavy flywheel from idle up. Leaned the idle mixture and its a miracle... responsive again.

dougn

well it's worth a try. i assumed it was too lean

Twood

See my post
''O2 sensor-What I have learnt"
and see if your problem sounds like what was happening to me.