My opinion.  Air fuel mixture is not set up properly.  Maybe a vacuum
leak was introduced when you resinstalled the engine.  Or, maybe
something was fixed and is affecting other parts of the engine.  The
o2 sensor on my 83 wbx takes 4 minutes to warm up and get fully
operational.  86 and newer have a heated sensor.  Not us.  :-(

Try disconnecting the O2 sensor, run the engine for 15 minutes or so,
then measure voltage with a digital voltmeter.  Should be 0.45VDC
roughly.

Maybe your engine is running lean when it gets hot?

Also, check the resistance on the Temp II blue sensor that connects to
the thermostat.

Also, I'm going to install a PVC valve this weekend.  Someone on the
list suggested that the black crankcase breather tower guts might be
falling apart due to age.

-- Craig

On Fri, 10 Dec 2004 07:49:45 -0800, Paul Guzyk <paullist@guzyk.com> wrote:
> I just had an 84 engine rebuilt.  I re-installed the engine.
>
> I believe I installed all the wires/hoses/etc correctly.
>
> The engine starts up immediately and sounds great, until it warms up.
>
> Once it warms up it idles quite rough although runs well at driving
> speed.  Should I be checking the O2 sensor?  What else?
>