How to Troubleshoot Problems for a 1991-94 Mercury Capri XR2 Turbo
XR2 Turbo model
Turbocharger Systems - 1.6L Turbo
Basic Operation
The turbocharger systom improves the engine power output by compressing the inlet air to a denser charge. Up to approximately 60 percent increase above the atmospheric pressure is attainable. It utilizes some of the energy in the hot exhaust gas to turn the turbine which drives the air compressor. The turbine and the air compressor comprise the turbocharger assembly, together with the exhaust bypass device, or the wastegate.
Since considerable heat is added to the air during compression, the air is cooled by routing it through a heat exchanger, the Charge Air Cooler (CAC). This reduces the possibility of preignition and engine damage from overheating. From the charge air cooler, the cooler air is ducted through the Volume Air Flow (VAF) meter to the engine intake manifold.
Boost Pressure Control
The boost pressure control system consists of a wastegate valve and a wastegate actuator. The actuator, which is controlled by turbo boost pressure, controls the wastegate valve, which opens and closes the exhaust gas bypass passage.
The amount of turbocharger boost is limited to a maximum of 56 kPa (8.1 psi) by the wastegate and actuator.
Under normal to moderate loads, the wastegate valve is closed and the intake air pressure changes in accordance with the engine rpm and the amount of exhaust gas. Under heavy loads, the intake air pressure in the air inlet duct reaches 56 kPa (8.1 psi), the pressure acts on the diaphragm and overcomes the force of the spring within the actuator, and the wastegate valve opens the bypass passage. As a result, the flow of exhaust gas applied to the turbine wheel drops, the rpm of the turbine wheel drops, and the boost pressure drops
accordingly.
Overboost Protection
If the actual intake manifold pressure reaches 77 kPa (1 1 psi) and the calculated intake manifold pressure (calculated from the amount of intake air and engine speed) reaches a predetermined level, the fuel injection will be cut to prevent engine damage. Under this condition the turbo boost gauge will be indicating in the red sector of the gauge.
Boost Gauge
The gauge on the dash indicates the amount of Boost produced. In typical driving, you will only see this gauge move when accelerating from dead stops or when flooring the accelerator. The gauge reads 0 most of the time when driving without much deviation in speed. Pressing on the gas a little will not show much on the Boost gauge. It will not move when slowing down. The turbo activates when you accelerate rapidly, as in, passing cars, from a dead stop.
The attached pictures will help you troubleshoot the most typical issues with this turbo, just follow the steps.
