How to Fix a Jeep Liberty That Hesitates When Acceleratingby Chris Orr
The Jeep Liberty was introduced by Chrysler as a sport utility vehicle in 2002. Troubleshooting acceleration issues involve testing several systems. Home mechanics can perform some of the repairs needed to solve the issue. Others may require a professional mechanic. The fuel or ignition system are the two places to begin troubleshooting. Some specialized tools, not generally owned by a home mechanic, are required.
Checking the Ignition System
Check the spark plugs. Fouled or mis-gapped spark plugs interfere with the fuel ignition process.
Check the spark. Using the Calibrated Ignition Tester, attach the lead to a spark plug boot or coil. Crank the engine and observe the spark. A bright blue spark indicates sufficient energy to fire the cylinder. A weak or intermittent spark is the same as no spark at all.
Check the wires or coils. Test resistance of the wires or coils using the ohmmeter. Replace them if they are defective.
Check the Fuel System
Check the fuel injectors. Dirty or clogged fuel injectors disrupts the flow of fuel to the cylinders. Use the automotive stethoscope against each injector, listening for a clicking sound indicating operation. Test the resistance of the injectors with the Ohmmeter. The proper range for the injector is 10.8 to 13.2 ohms.
Check the fuel pump. Low fuel pressure is a potential issue. Relieve the pressure on the fuel system. Remove the cap on the pressure test port on the fuel rail. Connect the fuel pressure test gauge and start the engine. If the pressure does not fall between 47.2 and 51.2 psi on 2002 and 2003 models or 56 and 60 psi on 2004 models with the NGC Powertrain Control Module, replace the fuel pump.
Test the Powertrain Control Module. Use the Onboard Diagnostic Scanner to determine if the Powertrain Control Module is malfunctioning. The PCM generally must be replaced by an authorized Jeep or Chrysler dealer.
Items you will need
- Calibrated Ignition Tester
- Automotive stethoscope
- Injector test light
- Fuel pressure gauge
- On-board diagnostic scanner
- "Jeep Liberty 2002-04 Repair Manual"; Len Taylor and Tim Imhoff; 2004
- spark image by Zbigniew Nowak from Fotolia.com