# 1998 chevy silverado 5.7 2wd



## timothy457226 (Nov 18, 2008)

I have a code and cannot pin point what it is.
Evaporator emission contorl circuit.
Truck run great but about every 500 miles it kicks the code.


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## mack1 (Nov 27, 2007)

timothy457226 said:


> I have a code and cannot pin point what it is.
> Evaporator emission contorl circuit.
> Truck run great but about every 500 miles it kicks the code.


Hi timothy and welcome to TSF :wave:

I'd reccommend that you buy a haynes manual. I have one but it starts at 1999. The section about the Evaporative Emission Control System talks about a system for drawing vapors from the fuel tank into a activated charcoal filed canister (EVAP canister). The PCM (computer) controls the function of the system including a test of the system integrity. The filtered vapors are injected back into the intake manifold when warmup conditions are met. Control valves at both ends of the system are controlled to do vaccuum tests of the fuel tank and lines. The sensor is in the tank for tank pressure. 

Just think, you may simply have a leaky gas cap.:grin:

The EVAP purge valve should be located at the top of the engine near or on the intake manifold. A line from it will lead you to the EVAP canister. A line from there will lead you back to the fuel tank. 

The book says that the system should last for the life of the vehicle, but if it fails, it will probably be the charcoal Canister or lines that are to blame.

Hope this helps,
Mack1


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