The engine may be hard to start run poorly and/or use to much fuel due to a fuel leak inside the intake manifold plenum. Commonly this is caused by a leaking fuel pressure regulator or fuel line. The fuel system will need to be pressurized with the upper intake manifold removed in order to determine the exact cause of the leak. Removing the "tuning valve" from the upper intake will allow for limited visual inspection without removing the upper intake manifold.
Engine Running Rich Due to Fuel Leak Inside Intake Manifold on Chevrolet S10 Blazer
Average mileage: 145,000 (145,000–145,000)
1 model year affected: 1993
1 person reported this problem
Fuel feed and return lines inside intake manifold crack decreasing fuel pressure and dumping raw fuel into the manifold and into the #3 cylinder. Replacement of the fuel lines is necessary for the repair. Fuel pressure regulator may also need replacement. The fuel line kit is called a "Nut Kit" at NAPA. The purge valve in the feed line may also develop a leak at a later date after replacement of the lines. Make sure to tighten and cap the valve.