hi,

i've been trying to figure out the source of my high warm idle (~1700 rmp instead of 950) for the past few weeks. here's the situation... the higher warm idle has been gradually increasing in rpm over the past 4-5 months and was not even noticeable until about 3 months ago when it started going above 1000. any way, in searching for the source i think i've found a/the problem with the cis system, but i don't know the source of the problem.

it turns out that the resistance reading from the coolant temp sensor (that goes to the ecu) reads about 1,500 ohms higher than it should (regardless of the coolant temp) according to the bentley diagram of resistance vs coolant temp. in other words, the resistance changes as a function of temp (ie high resistance when cold, low when hot) but is about 1,500 ohms higher than it should be. what is interesting is that this is only the case when the ignition is on. when the ignition is off, the resistance reading is dead-on.

thinking this was a sign that the sensor was on the fritz, i replaced it with a new one today only to discover that the new sensor acts the same way. i should point out i've gone over every aspect of the cis system numerous time and everything is functioning as it should (ie new computer, new cis motor, throttle switch works as it should, engine speed sensor works, engine wiring harness is good (replaced a few yrs ago), etc, etc).

my question is this... what could be causing this jump in resistance from the coolant temp sensor when the ignition is on? i've checked for bad wires and connections and no luck. could it be something else that is on the same electrical circuit as the cis system? (unplugging the fuse (#13) in the fuse box restores the resistance to normal but obviously disables the cis system). i think the other things that share that fuse are something like the turbo boost actuator valve(?) and the turn signals. i haven't had time to check them out for bad connections etc, but i'm being to wonder if that route is even where i should be looking or if there is someplace else i should look.

if anyone has any ideas or has witnessed something similar, let me know.

completely stumped...

erik