The thermstat is in the housing at the motor end of the upper rad hose. Two bolts hold it on. The EGR is on top of the intake manifold near the throttle body. It has a vacuum hose and two bolts. If I remember correctly the bolt are inverted torks. Which require a special tool to remove. Use a pair of locking plyers to remove, then replace bolts with standard ones.
It is in the front of the engine, to the right of the thermostat housing.
It is right beside of the thermostat housing, Right side of it. 2 bolts hold it on.
No,Its has to do with the EGR valve
The 1991 Geo Metro EGR valve can be located on the air cleaner housing. The valve will be on the back of the housing.
buy the haynes manual
The EGR valve for a Honda EX 1991 is at the top of the engine. It is at the front, just to the left of center.
The most common cause of that is a bad EGR Valve.
Next to the upper radiator hose, on the passenger side of the vehicle.
disconnect the hose and remove 2 bolts.
It is in the middle between the intake and the water pump.
That would more then likely be the EGR VALVE
check your egr valve or throttle positioning sensor