mzeitlin

I have a 2000 ES300.

Recently, the car - apparently - is misfiring only when it has been turned off hot and re-started soon after as, for example, going to a store to pick up something quick - engine off for a few minutes then cranked back on. After I re-start the car for the first 5 minutes or so the idle is rough and once I saw the check engine light blink, but it goes away. After driving for awhile, the engine smooths out and all is fine. It never happens when the engine is cold. According to the check engine codes - random cylinder misfire occurred (cylinder 1 and 5) - but it is intermittent.

Any thoughts where to check first? My O2 sensor is new (about 5,000 miles old) and seems to be working just fine (no engine codes). Again - engine runs great at cold start - up and continues to run great as engine gets hot (highway or other speed). Only when I shut off the engine and re-start soon thereafter, do I get idle hesitation and poor running.

Thanks

mzeitlin

Update: I am thinking I have a faulty engine coolant temperature sensor. I checked the resistance (while installed and hot) and found it to be in the "thousands" range .... it should be very low.
The sensor hasn't thrown a CEL code because it still has electrical connection (not broken), but it does seem to be 'worn out'.

Perhaps this is causing my hot engine to perform badly (at idle and stop line acceleration), but when cold, everything is fine.