[Wocketman]

Originally Posted by SoCal LS-L

Generally speaking, the EGR system basically recycles engine exhaust, which is essentially inert, back into the engine combustion chamber to take up space, allowing the air/fuel charge to be smaller and allowing better fuel mileage under low to medium engine load.

The goop is a normal by-product of combustion chamber soot and burnt off oil that is recycled thru piping that does not reach a high enough temperature for it to be burned "dry", it just collects over eons of engine operation and eventually impedes the exhaust flow past the temp sensor. Then the ECU thinks theres a problem with the EGR valve itself and kicks on the engine light, as in my case.

Ah, makes sense, thanks.