can pcv stop car from starting

[VonEmily]

Yes, a faulty PCV (Positive Crankcase Ventilation) valve can prevent your car from starting, but it's not the most common culprit. The issue typically arises when the valve is severely stuck open or closed, disrupting the engine's critical air-fuel mixture. When you turn the key, the engine computer expects a precise ratio of air to fuel. A malfunctioning PCV valve can create a significant vacuum leak, allowing unmetered air into the intake manifold. This leans out the mixture, making it too air-rich and fuel-poor to combust properly, resulting in a no-start condition, often accompanied by rough cranking or the engine starting and immediately stalling.

A PCV system's primary job is to reroute blow-by gases—unburned fuel and oil vapors that slip past the piston rings—from the crankcase back into the intake to be burned. This prevents sludge buildup and reduces emissions. A properly functioning valve is a one-way check valve that modulates this flow based on engine vacuum.

While a bad PCV valve can cause a no-start, it's more frequently responsible for drivability issues like a rough idle, high idle speed, or oil consumption. Before assuming the PCV valve is the problem, rule out more common causes. Here’s a quick comparison of symptoms:

Symptom	Faulty PCV Valve	More Likely Cause (e.g., Dead Battery, Bad Starter)
Engine Cranking?	Yes, engine turns over but won't "catch" and run.	No cranking at all, or very slow, labored cranking.
Recent Performance Issues	Often preceded by rough idle, oil leaks, or whistling noise.	May occur suddenly without warning.
Check Engine Light	Almost always illuminated with codes like P0171 (System Too Lean).	May not be illuminated if the issue is electrical.

If you suspect the PCV valve, testing is straightforward. With the engine idling, pull the valve out of its hose. You should feel strong vacuum suction, and placing your thumb over the end should cause the engine RPM to drop noticeably. If there's no suction or the idle doesn't change, the valve is likely clogged. Replacing a PCV valve is usually an inexpensive and simple fix.

[AshlynAnn]

It can, but it's pretty rare. Usually, a bad PCV valve just makes your car run rough or burn a little oil. For it to actually stop the car from starting, the valve has to be totally busted—like stuck wide open. That messes with the air pressure inside the engine, and the computer gets confused about how much fuel to add. The engine will crank and crank but never actually fire up. I’d check the battery and fuel pump first; those are way more common reasons for a no-start.

[DelDelaney]

From a mechanical standpoint, the answer is yes, due to a vacuum leak. The PCV valve is part of a sealed system. If it fails in an open position, it creates a major leak downstream of the mass airflow sensor. This unmetered air dilutes the air-fuel mixture, leaning it out beyond the combustible limit. You'll often find diagnostic trouble codes related to a lean condition (e.g., P0171) stored in the ECU. So while the car cranks, the mixture is too lean to ignite. Replacing the $15-$30 valve often resolves it.

[StOmar]

I had this exact problem with my old truck! It would crank strong but just wouldn't start. I checked everything—spark, fuel, you name it. A mechanic friend finally asked if I'd ever changed the PCV valve. I hadn't. He swapped it out in two minutes, and it started right up. He explained that the old valve was stuck open, acting like leaving a giant vacuum hose disconnected. It's a cheap part, so if you're stumped, it's worth a shot.