My 1990 Reatta has unpredictable starting and idle problems. Starting hot or cold the idle will sometimes properly advance properly and gradually idle back as the engine warms. However,unpredictably it will sometimes run at 2000 rpm and stay there for from two to fifteen minutes of driving before backing down to normal idle speed. Occasionally it will require throttle to fire and will stall immediately if throttle is released. This particular condition may begin when starting hot or cold, or when sitting at a light, and will last for several minutes of driving. The check engine light previously would go on sometimes and replacing the 02 sensor, and the idle air control valve stopped the warning light, but did not fix the above problems. These problems are intermittant and cannot be caused on demand, so no mechanics or dealer has been able to diagnose them. Their advise is to wait until it happens all the time. Is there any help for this?
