* Dirty or Failing Mass Airflow Sensor (MAF): A dirty MAF sensor provides inaccurate air readings to the engine computer, leading to a rich or lean fuel mixture, resulting in rough running and poor fuel economy. This is a relatively inexpensive part to replace.
* Failing Oxygen Sensors (O2 Sensors): These sensors measure the oxygen in the exhaust and help the engine control the air/fuel mixture. Faulty O2 sensors can cause inaccurate readings, leading to poor fuel economy and rough running. Again, relatively inexpensive to replace, but you might need several (one for each bank of cylinders).
* Spark Plugs and Wires: Worn-out spark plugs or damaged ignition wires can cause misfires, leading to rough running and poor fuel economy. These are relatively easy to replace, but it's crucial to use the correct type and gap.
* Crank Position Sensor (CKP) or Cam Position Sensor (CMP): These sensors tell the engine computer where the crankshaft and camshaft are positioned. A failing sensor can cause the engine to run poorly or not start at all. This is a more serious issue requiring more specialized tools for replacement.
* Throttle Body Issues: A dirty or malfunctioning throttle body can restrict airflow, causing rough running and poor fuel economy. Cleaning it is relatively simple; replacement is more involved.
* Vacuum Leaks: A vacuum leak can disrupt the engine's air/fuel mixture, leading to rough running and reduced fuel economy. These are notoriously difficult to find, often requiring a smoke test.
* Fuel Injectors: Clogged or failing fuel injectors can deliver inconsistent fuel to the cylinders, resulting in poor performance and fuel economy. Cleaning is possible, but replacing them might be necessary.
* Internal Engine Problems: At 106,000 miles, issues like worn valve seals, piston rings, or other internal engine components could be contributing factors. This is the most serious and expensive potential problem.
What to do:
1. Get a professional diagnostic scan: Take your Jeep to a qualified mechanic or auto parts store that offers diagnostic scans. This will give you concrete data on what's wrong. The codes will greatly narrow down the possibilities.
2. Don't guess and replace parts randomly: Throwing parts at the problem is expensive and might not solve anything. Let the diagnostic scan guide you.
3. Check for simple things first: Ensure the air filter is clean. A severely restricted air filter can cause some of the symptoms you describe.
The fact that the rough running is primarily at startup suggests a cold-start issue, but the poor fuel economy indicates a more persistent problem. The combined symptoms strongly suggest a need for professional diagnosis. Ignoring this could lead to further, more costly damage.
