What causes unstable idle and engine reversal in Nissan Paladin?

[McAllie]

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.

[VonRonan]

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.

[SanKimberly]

Unstable idle accompanied by abnormal vibrations is commonly seen in Paladins. I suspect carbon buildup is mostly to blame—a dirty throttle body affects air intake, causing engine RPM to fluctuate. Faulty ignition coils or aged spark plugs can also lead to poor ignition, triggering intense shaking like reverse motion. If the fuel injectors are clogged, uneven fuel supply worsens, especially with bad gasoline. Contaminated or damaged sensors like the mass airflow sensor or throttle position sensor can cause the ECU to misjudge and mismanage controls. For simple DIY fixes, try cleaning related components or replacing spark plugs. If issues persist, don’t delay—seek a mechanic promptly to prevent engine damage.

[MaryDella]

I've dealt with this kind of idle vibration before. The Paladin's instability might be caused by carbon buildup in the throttle body or sensor malfunctions. What's referred to as engine reversal feels more like severe misfiring vibrations. The first step is to check the ignition system to see if the spark plugs are old and need replacing. A dirty air filter should also be cleaned or replaced. Poor fuel quality can worsen the problem, so it's better to choose higher-quality fuel brands. If the carbon buildup isn't severe, you can clean the throttle body yourself. If the vibration persists, check the fuel pump or go to a repair shop to scan for trouble codes. For prevention, regular maintenance is the most worry-free approach.

[CatherineAnn]

Unstable idling accompanied by a reverse illusion is mostly due to inadequate maintenance. Carbon buildup in the throttle body blocking air intake or faulty ignition coils are the most common root causes. Worn spark plugs or a clogged air filter can make the engine run rough. Malfunctioning sensors like the oxygen sensor or throttle position sensor can also mislead the ECU in controlling idle speed. The so-called reverse sensation is actually vibration from unsynchronized piston movement, not actual reverse rotation. Simple fixes include cleaning the throttle body, testing spark plug performance, or replacing aged components. For prevention, changing the air filter every six months and using high-quality oil are crucial. If there's no improvement, seek professional diagnosis immediately to prevent further damage.