My 2002 Diamonte LS continues to have an interesting problem (has had this issue for years)... When driven for at least a half hour - freeway driving mostly - and then parked for more than 30 minutes if I restart the car the idle is very rough - almost stalls - if I give it some gas it returns to normal in a few seconds.. Any troubleshooting ideas? Less than 30 minutes no issue.... More than about an hour no issues..

I did clean the throttle body which made a difference in the idle during normal driving circumstamces when you stop in traffic but did not impact this issue.

Thanks

how old are the plugs ?

try some injector cleaner on the injectors

recheck the timing

Plugs are original... Mileage is only 62K.. Mechanic at dealer when flushing tranny said he felt the rough idle between test drives and checked the distributor cap as he said they can form hairline cracks that let moisture in - this was not the problem. From a cold start no issues...

Otherwise the engine is very smooth 98% of the time - like new in fact.

What are the ambient temps when the problem occurs? Sounds like vapor lock, where the fuel boils and vaporizes in the fuel rail, then the mixture is off when vapor instead of liquid is injected. The timing of the problem is right because after an hour it cools enough to re-condense.

Seem to remember some kind of bulletin or tech-talk on this issue

This could be slight issue with Intake Air Temp, the sensor helps adjust fuel spray along with the air flow meter on warm start ups . It can be creating a rich fuel start up causing similar to partially flooding. Also running low or poor octane for a long time will cause this also. This and the Intake Manifold Air temp sensor can be a culprit in this instance. As for cheap fuel , poor octane balance can deteriate a spark plug fastly over time.