A replacement carburetor or throttle body injector is a cost-effective solution only when a “carburetor failure” was correctly diagnosed and the replacement carburetor is properly installed.
Tips for Successful Installation
- Identify the correct replacement carburetor
- Carefully mark all of the hoses and accessories connected to the old carburetor or throttle body injector before removal. Make a sketch or take a picture if necessary.
One of the most frequent causes of improper installation is incorrect connection vacuum hoses to the replacement carburetor.
- Always flush the fuel line before installing the replacement carburetor.
- Install a large capacity in-line fuel filter. The single highest frequency cause of failure is contamination in the fuel line.
- Every carburetor and throttle body injector is pre-adjusted to OEM specifications. Fine adjustment of the curb idle, idle mixture, fast idle and/or choke setting may be necessary depending upon the vehicle. Carefully follow the instructions and sequence of adjustments in the information enclosed with the replacement product or supplementary repair manual.
Troubleshooting
If the engine runs rough despite repeated efforts to adjust idle screws, check for:
- Loose or cracked vacuum hoses. Hoses must be properly connected and leak free. Look for uncapped vacuum pipes, loose fittings or cracked hoses. To check for leaks, disconnect the hoses one at a time and place a finger over the pipe while the engine is running. If the engine RPM changes or smoothes out, there’s a leak that must be fixed.
- Ruptured vacuum diaphragms or leaks in thermal switches connected to hoses. Check EGR valve, distributor vacuum advance, power brake booster, heated air door actuator and air temperature sensor in the air cleaner, transmission modulator and other vacuum operated components.
- Leaking intake manifold. All bolts and gaskets must be tight. The best way of finding vacuum leaks is to use an electronic vacuum leak detector. It has variable sensitivity so that even small leaks can be pinpointed. If an electronic detector is not available, squirt a small amount of water on the suspected leak location while the engine is running. If the liquid is pulled into the manifold, it leaks. If a tachometer or vacuum gage is connected, the RPM or vacuum reading will momentarily change as the fluid is sucked into the manifold.
- Defective PCV Valve. This can cause improper air mixture and rough idling.The PCV valve should be replaced every 10,000-12,000 miles, and whenever a replacement carburetor or throttle body injector is installed.