If the hot idle speed on EFI models falls below preset values, you should check for low fuel pressure.
Low fuel pressure could be caused by a hole in fuel hose inside the tank. If fuel pressure is low, it
may require removal and inspection of fuel feed hose from pump to filter.
If the hot idle speed fluctuates or increases while running, you may have a problem with the engine
temperature circuit. This problem can cause high idle, rough running, and black smoke coming from
exhaust. You can verify this problem by monitoring scanalizer readings when the problem occurs.
Normal reading should be >284⁄F. If readings are observed to be lower, then diagnostics are
required. Most of the time this condition will not register a trouble code. You should perform a thorough
wiggle test on ETS circuit as described in Service Manual. Connections have been found to
be the problem in most instances. If no problems are found with wiring or connections, then a new
sensor may be necessary.