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Emission Control Maintenance Bruce Bonebrake does an emission test on a 1998 Jeep, then performs emission system service including plugs, wires, distributor rotor, MAP sensor, fuel injectors, O-rings and air filter. From "Weekend Mechanic" episode WKM-413

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Emissions Service: Spark Plug and Plug-Wire Replacement

• With the air duct assembly out of the way, it’s important to disconnect the battery before working on the spark plugs and distributor.

• Remove the old spark plug wires and spark plugs, making sure to label the wires with the cylinder and spark plug location.

• Loosen the distributor cap mounting screws and remove the cap and spark plug wires.

• Using a ratchet wrench with the spark plug bit, remove the old spark plugs.
  

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  Once the fuel-rail bolts are removed, carefully loosen and remove the fuel rail.

• Replacing the distributor rotor is fairly simple. The old one comes off, and noting the position of the slot, the new rotor goes on simply by pushing it into the slotted distributor shaft.

• Starting with the number 1 plug-wire, remove the old wire measure it to the new wires and install the correct length wire to the new distributor cap.

• Be sure to label the new plug wires as you go. Continue installing the other plug wires and finally, install the new ignition coil wire.

• The new distributor cap and plug wire assembly is installed and tightened down.

• And the plug wires are connected to their corresponding spark plugs clipping the wires neatly in place.
  

  New, and newly serviced, injectors installed in the fuel rail

• With the throttle cable and bracket out of the way, the fuel line retaining clip comes off.

• A fuel line disconnect tool slips over the fitting and releases the internal spring so the line can be pulled off.

• Disconnect the fuel rail electrical components and remove the fuel rail mounting bolts.
  
  

  A bad injector was replaced with a new one, and new O-rings were added to the remaining injectors.

  Important: Before removing the fuel rail, it's important to blow off the debris around the injectors so it doesn't get into the intake manifold.

• After cleaning, carefully dislodge and pull the fuel rail out.

• Pry the retaining clip off and disconnect the injector from the rail. Be sure to remove the old O-ring if it's stuck in the rail.

• It's always a good idea to compare a new part to the old one. Our new injector looks good. Before installing the new injector, apply some oil or fresh grease, to the fitting, to make installation easier. With the injector firmly seated, the retaining clip is installed.
  

  	Reinstalling the fuel rail
  	The fuel rail, reinstalled, with newly serviced injectors.

• It's important to have a fire extinguisher nearby when working on the fuel system.
  
  
• Continue with the other fuel injectors, replacing the entire injector or just the o-rings as necessary.

• To replace the interior o-ring you'll have to remove the injector from the fuel rail. The serviced fuel rail goes back in and is secured with the mounting bolts.

• The fuel rail electrical connectors are re-installed and the fuel line is re-connected.

• The retainer clips into place, the mounting bolts are tightened down and the fuel rail is secured.

Emissions Service: Cleaning the Throttle Body And Installing a New MAP Sensor

• Disconnect the TP (throttle position) sensor from the throttle body.

• Disconnect the MAP sensor.

• Loosen and remove the throttle body mounting bolt.

• The throttle body comes off as well as the old gasket. Remove the screws that hold the MAP sensor to the throttle body and disconnect the vacuum port.

• Carb cleaner makes quick work of cleaning the throttle body, both inside and out. Use the nozzle extension to clean out the map sensor port.

• The new MAP sensor simply bolts on.

• A new gasket goes in place and the clean throttle body is re-installed.

• Reconnect the TP sensor. Hook up the map sensor connection and reconnect the idle control valve.

• The throttle cables and bracket can be re-installed and the cable bracket fasteners are installed and tightened down.

• The cruise control cable is re-connected, the throttle cable is re-attached and the throttle spring goes into position and the clean throttle body and cable linkage works well.

• While your at it, it's a good idea to install a new, clean air filter. About 20 percent of vehicles that fail an emissions test simply need a new air filter.

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