Delay speed, weakness to climb a slope. 2004 Jeep Liberty

ANSWER : Hi there – first check is for any problem codes, whether the Check Engine light is on or not. I would bet that either the thief damaged something else not apparent, or something was not re-connected properly when the vehicle was repaired. If you can capture any diagnostic codes and other symptom information, and re-send them to us, we are happy to help you diagnosis this problem.

ANSWER : Hi, thanks for writing in. This is a common problem associated with fuel/air delivery which is very commonly related to what is called a mass airflow sensor. This monitors the flow of air intake into the throttle body as it is mixed with fuel to deliver the right air/fuel mixture into the motor. When this is not working properly, this will cause this kind of hesitation or surging when trying to accelerate. I would recommend having an expert from YourMechanic come to your home or office to confirm a diagnosis on the issue and make or suggest the necessary repairs or replacements.

ANSWER : Hi there – most likely, the "thunk" you describe is coming from a weak or failed motor mount. It is allowing the engine to move about when you apply the accelerator pedal, and the engine is hitting something in the engine compartment. I recommend an engine mount inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, confirm this diagnosis, and give you an accurate assessment of damage and cost estimate for repairs.

ANSWER : The two engines you cite use completely different computers (PCM/ECM) and the casting numbers are completely different. You can try it but you are all but guaranteed to have start up and operational problems due to incompatibility with the existing engine computer. As far as the crank trigger wheel, on the 2004 engine, there are 32 teeth, while both versions (two different engines were used in 2002) of the 2002 3.7L engine used a 12 tooth wheel. Inasmuch as the engine is basically run by the computer, the allowed interchanges are only those listed in the OEM catalog. If you use a non interchange engine, you have to change out the vehicle wiring harness and the computer and even that is not guaranteed because all of the other microprocessors on the vehicle, such as the immobilizer system, won’t recognize the new PCM. It is not just a software issue either as the actual hardware in the PCM is different in the two years. If you need a replacement engine, you will find an EXACT interchange, guaranteed to be compatible, if you search at Car-Part.com. If you are interested in an engine installation (OEM to OEM), YourMechanic professionals in certain locales can assist with that. Please simply inquire based on your locale. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.

ANSWER : You should have the vehicle scanned. The data from the speed sensor needs to be checked to see if the transmission or engine is the cause of the jerking. You may have a transmission solenoid that’s not shifting correctly, an engine misfire, or a sensor malfunction. Have a certified mechanic, like one from YourMechanic, scan and test your vehicle for you to properly diagnose the car’s jerking symptom.

ANSWER : Hi there – your symptoms suggest a fuel supply issue, quite likely a fuel pressure check valve or fuel pressure regulator issue. Either of these can allow fuel pressure in the injection system to leak down while the vehicle sits. This makes the fuel pump work harder when the vehicle is next started, taking longer to get fuel pressure up to specs. I recommend a hard starting inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.

ANSWER : No. Each computer is made for the a specific vehicle and matches to the VIN. If you need a new computer installed, you will have to order this for your model from your local dealership and have them install it – they will have the computers needed to program the new computer and set this up properly for you.

ANSWER : Hi there. Check the turbo on the engine. With the loss of power until the vehicle is driven normally after 100 meters and the lack of power going up steep hills, the turbo could have failed causing the engine to lose power. Remove the intake hose to the turbo and start the engine. Look to see if the turbo is spooling up or not. If its not spooling up, then the turbo shaft could be seized and would need replaced other wise the waste gate could be not functioning causing the turbo to stop boosting. I recommend seeking out a professional, such as one from Your Mechanic, to help you diagnose your loss of power.