Q: At idle, my car uncontrolably surges rpm up to 2500rpms.

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At idle, my car uncontrollably surges rpm up to 2500rpms. I can smell unburnt fuel. I check for vacuum leaks, Could not find any. I first cleaned out the Air Idle Control Senor, No luck,,, second I replaced it with one off a donor car from a salvage yard. I replaced some vac hoses, and the PCV valve. I replaced the valve cover gaskets (oil leaks), check and re-gaped the spark plugs. Disconnected the battery to reset the CPU... I checked the distributor. I cleaned some senor connections with electrical cleaner. I replaced the CPU about 1 1/2 yrs ago for a donor car from a salvage yard.

I am at a lost at figuring this out... unfortunately I do not have the money to have a "diagnostic" done on it. 1993 Honda Civic DX 5speed Manuel 1.5L

What else can I try.... I state (TX) inspection is due in two weeks.. I need to have this problem fix by that time.

Kate chillwill2230@hotmail.com

My car has 293400 miles.
My car has a manual transmission.

Hi Kate, Try checking themass air flow sensor as this will definitely cause engine surging problems when it is dirty or has a poor connection. This may also explain the raw fuel smell as well. As you may know, the MAF relays information to the ECM which uses this to make adjustments to fuel supply to the motor. A dirty or faulty sensor can cause an imbalanced air/fuel load to be supplied to the motor which results in an over fueling or under fueling situation depending on the conditions. This type of inconsistent fuel supply to the motor may cause a hesitation, loss of power, a jerking reaction, potentially a bit of black exhaust smoke and typically a strong smell of fuel when this sensor is malfunctioning. You may also want to check for vacuum leaks as well. Excess air flow into a leaking vacuum line or intake gasket could also cause the motor to surge as you describe. If you need further help with this, please reach out to us here at YourMechanic as we are always here to help.

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