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- Throttle Body / Throttle Position Sensor: Make sure the throttle body is cleaned, the butterfly is closing fully, and the TPS switch is adjusted and working correctly. Perhaps the TPS switch is slightly loose, and the engine computer cannot tell whether you want to rev up or down. Search the Brickboard or check a manual for details on how to adjust the TPS.
- Idle Air Control Valve: This unit controls engine speed at idle. When it fails, you will have a rough idle. However, it should not cause gas mileage problems that extreme.
- Electical Connectors: See if any electical connectors are dangling loose. Perhaps the TPS or IAC electrical connectors were not snug, and worked their way loose.
- Fuel Pressure Regulator: Verify that raw gas is not leaking thru to the intake manifold. Search the Brickboard for details on troubleshooting this part.
- Vacuum Leaks: Check for vacuum leaks around the intake manifold (perhaps it wasn't tightened properly). Also check ALL vacuum lines, especially in the "accordian" tube from the MAF meter to the throttle body.
- Volvo Mechanic: Is your mechanic a Volvo specialist? Did he replace the cylinder head only, or other parts too? Were new engine sensors used (engine coolant temp sensor, knock snesor)? What mileage and condition was the car in before the repair? It is possible that one or more of these items really need to be replaced anyway, especially when it comes to vacuum lines. I would perform MINOR troubleshooting myself, then then take the car back to the same shop to see what they say next. For the cost of a Volvo 240 engine replacement, you should get at least seven days of automotive happiness... maybe even ten!
[[ southern fried volvo '91 240 148k mi ]]
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