Tech Stuff

The dreaded engine surge

A crankshaft position sensor features a permanent magnet and generates an AC signal as the toothed position wheel sweeps past the sensor.
A crankshaft position sensor features a permanent magnet and generates an AC signal as the toothed position wheel sweeps past the sensor.

In this article, we'll discuss engine idle issues, surging and "hunting" problems. First let's cover the "basics" in terms of the possible causes of engine surging/hunting, where engine speed suddenly (or slowly) changes.

A wide variety of issues can prompt an engine surge. The problem may involve an annoying change (up/down) of engine speed while cruising at a steady pace, a low drop (or even cut-out) at idle or when approaching a stop, a wild high engine speed of several thousand rpm followed by a drop to near zero, etc.

• Transmission not locking up (or slipping)

• Vacuum leak

• EGR valve stuck open

• Dirty/sticking IAC (idle air control valve) (P0505)

• Engine temperature sensor

• Knock sensor

• Clogged EGR ports

• Variable valve timing solenoid clogged/sticking

• Air in cooling system

• MAF connector loose/intermittent connection/faulty MAF

• Fuel system pressure issue

• Clogged fuel filter

• Plugged/restricted exhaust

• Crankshaft position sensor (P0336)

• Power steering pressure sensor circuit

• A/C compressor cycling on/off due to low refrigerant

• Faulty TPS

• Clogged/restricted catalytic converter

• Ignition system

• PCV

• High pressure oil system (diesel)

Tags: Fuel injectors 
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