Porsche Enthusiasts Club Forum

Car is an 84 chassis with an 86 motor swapped in.

I have just finished a whole lot of 'tidy up' work under the intake manifold - fuel injector reseal, throttle body reseal, replacing vacuum lines, cleaning ICV and replacing ICV hoses, cleaning grounds, etc.

The car now starts perfectly fine but will not hold idle at all - it instantly stalls unless I hold the throttle, and it revs irregularly (seemingly out of sync with the pedal) if I do this.

I have checked all vac lines, swapped DME, disconnected one injector (in case of FPR failure), and tried disconnecting the TPS.

Any ideas? I have that sinking feeling...

Is the routing of the idle control valve correct with arrow facing the correct direction?

Double check all of the sensor connectors are secure and no wires are broken, especially the flywheel sensor at the back of the engine (check its gap).

And of course DME relay - maybe jumper the fuse box connectors.

ICV arrow is pointing towards the intake manifold.

Wouldn't the speed/ref sensors cause a no-tach-bounce type of issue?

DME relay has been swapped with no result

sounds to me like the engine is being starved of air on idle, and then erratically supplied when you add throttle. had a very similar condition on my DeLorean, which turned out to be the idle valve playing up and restricting air flow. Maybe the air flow sensor?