Pontiac Fiero 1984-1988 Repair Guide

Exhaust Gas Recirculation System (EGR)

Print

OPERATION





Click image to see an enlarged view

Fig. Fig. 1 Cross-sectional view of the EGR valve operation

The Exhaust Gas Recirculation (EGR) System is used to lower the oxides of nitrogen (NOX) emission levels caused by high combustion temperature. It does that by decreasing combustion temperature. The main element of the system is the EGR valve mounted on the intake manifold (4 cyl.) and on the exhaust manifold (V6). The EGR valve feeds small amounts of exhaust gas back into the combustion chamber.

The EGR valve is opened by ported manifold vacuum to let exhaust gas flow into the intake manifold. The exhaust gas mixes with the air/fuel mixture as it moves into the combustion chamber. Very little exhaust gas is allowed to enter the valve, and non at idle.

TESTING





Click image to see an enlarged view

Fig. Fig. 2 Some EGR valves may be tested using a vacuum pump by watching for diaphragm movement

Too much EGR flow at idle, cruise or cold operation may cause the following conditions:

  1. Engine stops after cold start.
  2.  
  3. Engine stops at idle after deceleration.
  4.  
  5. Vehicle surges during cruise.
  6.  
  7. Rough idle.
  8.  

Too little or no EGR flow allows combustion temperatures to get too high during acceleration and load conditions may cause the following conditions:

  1. Start knock (detonation).
  2.  
  3. Engine overheating.
  4.  
  5. Emission test failure.
  6.  

REMOVAL & INSTALLATION





Click image to see an enlarged view

Fig. Fig. 3 Location and mounting of the EGR valve-2.8L engines



Click image to see an enlarged view

Fig. Fig. 4 EGR valve location and mounting-2.5L engines

  1. Remove the air cleaner on the 4 cylinder engine.
  2.  
  3. Disconnect the vacuum line.
  4.  
  5. Remove the bolts and remove the valve from the manifold.
  6.  
  7. Before installation, start the engine for 5 seconds to blow out the carbon in the manifold.
  8.  
  9. Install the valve with a new gasket to the manifold and torque the attaching bolts on the 2.5L L4 engine to 16 ft. lbs. (22 Nm). Torque the two nuts on the 2.8L V6 engine to 15 ft. lbs. (20 Nm). Install the vacuum hose. Start the engine and check for exhaust leaks.
  10.  

CLEANING





Click image to see an enlarged view

Fig. Fig. 5 Disengage the vacuum line from the EGR valve



Click image to see an enlarged view

Fig. Fig. 6 Unfasten the EGR valve retaining bolts ...



Click image to see an enlarged view

Fig. Fig. 7 ... then remove the EGR valve



Click image to see an enlarged view

Fig. Fig. 8 Remove the EGR valve gasket ...



Click image to see an enlarged view

Fig. Fig. 9 ... then use a gasket scraper to remove any of the old gasket residue

  1. Using a wire wheel, clean the carbon deposits from the mounting surface and around the valve.
  2.  
  3. Scrape any carbon deposits around the valve outlet with a suitable tool.
  4.  
  5. Clean all mounting surfaces.
  6.  

 
label.common.footer.alt.autozoneLogo