On a warm day, when restarting the engine, as when leaving a gas station or coffee shop after a short visit, the 7M-GE and 7M-GTE engines may exhibit weak idling, hard starting and putting around at 500 rpm for a short period. If this happens only very occasionally it is perfectly normal and is caused by a condition called HEAT SOAK, which happens, after shutting off the engine. After shutdown the water pump and fan are no longer cooling the engine so the heat from inside the engine comes out into to engine bay cooking everything in its way, EFI sensors say "Wako sure is hot in here," gasoline in the fuel rail on the intake manifold is boiled {not to mention a host of other thermodynamic conditions that occur after shutdown}. All Engineering levels are taxed.
To combat this inherit EFI {Electronic Fuel Injection} problem a number factory installed electronic and mechanical engine control systems are used, but under certain conditions they fail to correct the problem completely. For the most part EFI is a wonderful system allowing great fuel economy and silky smooth drive ability so a small bug like HEAT SOAK is still a more livable end than going back to carbs. If this rough idling symptom is happening more often than seems normal there may be a problem with one or more of the following: Cold start injector time switch, Bad Fuel, Throttle position sensor, Plugged or restricted fuel filter or gas cap, Idle speed solenoid air valve (ISC Valve), Fuel pressure, 2 speed fuel pump system, Head Gasket, Air intake leaks, Engine mechanical, Fuel pressure up VSV {vacuum switching valve}.
Other points to remember about the idle speed control valve (ISC valve) are: After shutting of the engine you should here a faint clicking sound for a short time after the engine is killed, this is normal operation.
Unplug the wire at the ISC valve after the valve makes its normal clicking noise after engine is shut off, will cause the engine to run in high idle when the engine is restarted. This is a good sign that the ISC valve is working correctly.
When E1 & T1 in the check connector (Diag Block) are shorted, this will cause the valve to go to a standard closed position. This is the first step in setting the curb idle and ignition timing.
Failure of the ISC valve is not a common problem, what should be checked is the seat section of the valve that sits in the intake manifold. When the ISC valve is removed, this seat will remain in the hole in the intake manifold. This seat valve will get sticky and not work smoothly due to excess carbon and deposits in the intake manifold.
The Bardal Super Tune kit comes with a can of gunk for the fuel tank and a can of gunk to be slowly sucked into the intake manifold while the engine is running at high idle. This gunk stuff works great. Also included in the Bardal super tune kit is a can of gunk that is sprayed into the intake plumbing, and throttle body. Spray this gunk into the airline going into the idle speed control valve. Presto changeo the valve will most often work fine again. Wins also makes a good fuel injection cleaning kit that works wonders as well. The Wynns kit does not have the can of gunk spray, but it does a great job on the injectors and intake manifold.
When the VSV for fuel pressure up is working correctly it allows the fuel pressure regulator to receive atmospheric air pressure to its vacuum port when the engine is hot. To test this VSV you can unplug the vacuum line from the fuel pressure regulator and start the car to see if the vehicle starts normally. If it does the fuel pressure up VSV is the problem.
