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EGR Blockoff Plate

Theory:

The EGR (exhaust gas recirculation) valve is an emmission control device to lower the combustion temperature in the engine. A lower combustion means lower NOx (nitrogen oxide) emissions. It accomplishes this by allowing exhaust gases to be recirculted into the intake manifold through a EGR value (see illustration). The exhaust acts as a inert gas in the combustion chamber forcing the combustion explosion not to be effective as normal because of the presence of this inert gas. Or as some people rationalize it, it "dirtys" the intake air to not burn as well as it should. Ironically, the EGR emission control actually causes an increase HC (hydrocarbon) emmissions.

Most states test for 2 emissions: 1) CO (Carbon Monoxide) and 2) HC. The NOx test requires very expensive specialized equipment and is only tested in a handfull of state (i.e. CA). So if you live in a state that doesn't test NOx, installing a EGR blockoff will actuall reduce your emissions test results (see HC statement above). If you live in CA you have a problem. In addition to the emission concern, the CA emissions equipped cars have a sensor that will report a trouble code (see Engine Codes) if the EGR is blocked-off. I have heard that all '94+ cars had the CA EGR installed, but can't confirm this since I don't have a '94+.

Rationale:

The reason I installed my blockoff plate was beacuse my EGR valve failed at the 105k mile mark, and was causing the infamous "idle surge" problem. This fixed the problem. Theoretically the since the engine is burning more purely a slight increase in power should be seen, though I didn't notice anything significant to confirm this. Also, the intake is also running much cooler since no hot exhaust gases are being injected to it, thereby helping the intercooler and having the intake air nicely cooled and dense.

Procedure: (see illustration)

(specifically for 1991 FWD 2.0L turbo, others will be similar if not identical)
  1. Remove the battery (10mm bolts)
  2. Remove the two bolts holding the EGR valve to the intake manifold (12mm bolts)
  3. Pull the EGR valve off enough to be able to get the metal gasket between the valve and the intake manifold.
  4. Take out the gasket and use it as a model to create a blockoff plate. There are two small holes for the bolts you just removed, and two large holes where the exhaust gas goes through which we want to block. Any machine shop could make you one out of some scrap aluminum for very cheap. All they (or you) need to do is make the piece the same size as the gasket (the thickness should be about 1/8 inch). And drill out the two bolt holes, and you done (here is a picture of the EGR blockoff plate). Incidentially, Frank Szymkowski makes a EGR blockoff plate for $10.
  5. Place your newly made blockoff plate in place and bolt the entire assembly back on (torque to 11-16 ft.lbs., intake is aluminum so DON'T overtighten or you may strip it).
  6. Reinstall battery

Notice:

Federal and state laws forbid any intentional modification to emission control devices. The above procedure is for educational purposes only.
 

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Copyright 1999, Brad Bauer