What causes unstable idle and engine reversal in Nissan Paladin?
2 Answers
The reasons for unstable idle and engine reversal in Nissan Paladin are as follows: Idle switch not closing: The engine speed signal determines the fuel injection quantity and timing, but the engine is operating under idle conditions with reduced air intake, leading to an overly rich mixture and increased engine speed. Faulty idle control valve: When the idle speed exceeds the set value, the ECU commands the idle control valve to reduce the intake bypass, decreasing air intake and lowering engine speed. Issues such as sticking due to oil contamination or carbon buildup, or incomplete throttle closing, can prevent the ECU from properly regulating idle speed, resulting in unstable idle. Intake manifold air leak: The opening of the idle control valve and the air intake strictly follow a specific functional relationship, where increased valve opening corresponds to increased air intake. An air leak in the intake manifold disrupts this relationship, preventing the air flow sensor from accurately measuring the actual air intake. This leads to inaccurate air intake control by the ECU, causing unstable engine idle.
This issue really needs to be addressed properly. As someone who frequently tinkers with cars, idle instability coupled with the sensation of engine reverse rotation can be quite frustrating. Older Nissan Paladins are prone to this problem, mainly due to severe carbon buildup in the throttle body, where dirt clogs the intake passages, causing unstable RPMs or even shaking. It could also be an ignition system failure, such as worn spark plugs or faulty ignition coils, leading to poor spark generation. Clogged fuel injectors can cause uneven fuel supply, resulting in vibrations. The so-called reverse rotation is actually an illusion caused by unsynchronized piston movement, not actual reverse rotation. I recommend first cleaning the throttle body and checking the condition of the spark plugs yourself. If that doesn’t help, take it to a professional shop to scan for ECU trouble codes. For prevention, using high-quality fuel and regularly maintaining the air filter can avoid most potential issues.
