"jdoe" > wrote in message news:2SZTd.3761$r55.3614@attbi_s52...
> The actual IAC could be bad. Another thing that causes this is the coolant
> temp sensor. The one that mounts in the driver's side of the cyl. head. On
> mine it was the IAC BTW. Before you replace anything though try one quick
> thing. with the engine idling create a vacum leak (pull off a hose). Than
> seal the leak with your finger than reopen than plug the hose back on.
Than
> see if the engine behaves itself.
> Larry

Good advice. I always look for a vacuum leak first and pinch hoses to check
for any abnormal airflows while listening to the rpm. If RPM drops when the
hose is pinched, that is a likely source.
A full featured scan tool will do more than just read codes. On some of
them, you can read the actual coolant temperature (or any real value from
sensors) and compare this to the actual engine temperature. Somtimes this is
a lot beter than just replacing sensos since it tests the entire signal run
from the sensor to the computer.

Unfortunately, everything that I have seen in scan tools, short of the
factory tools only does reads of the computers. They do not have the
ablility to perform actuator tests. On another older vehicle, I had a
diagnostic tool that could perform actuator tests like controlling valves
and even the idle motor. I miss that ability on my lw300. A tech 2 tool
would be nice but what shade tree mechanic can afford one of those?
Oppie