can a broken egr cause a car not to start

[MacChloe]

Yes, a severely malfunctioning EGR (Exhaust Gas Recirculation) valve can absolutely prevent your car from starting, although it's not the most common cause. The issue typically arises when the valve fails in the fully open position. This allows a continuous, unregulated flow of exhaust gas into the intake manifold, which excessively dilutes the air-fuel mixture. The engine's computer (ECU) cannot compensate for this large amount of inert gas, resulting in a mixture that is too "lean" to combust properly during startup.

The most frequent symptom you'll notice before a complete no-start condition is a very rough idle, stalling, or a significant lack of power. The engine might crank normally but will not fire up. This is distinct from a starting problem caused by a weak battery or faulty starter motor, where the engine turns over slowly or not at all.

Diagnosing this requires a professional scan tool to read trouble codes. A code like P0401 (EGR Flow Insufficient) or P0405 (EGR Sensor A Circuit Low) can point to the valve. A mechanic can also perform a physical test by attempting to manually move the valve diaphragm. Replacing a stuck EGR valve is often the solution, but it's crucial to also inspect the EGR passages in the intake manifold for carbon blockages, which can cause similar symptoms.

Diagnostic Clues for EGR-Related No-Start
Primary Symptom	Engine cranks normally but fails to ignite.
Common Preceding Signs	Rough idle, stalling at stop lights, noticeable power loss.
Likely Diagnostic Trouble Codes (DTCs)	P0401, P0405, P0406, P1406.
Probable Failure Mode	EGR valve stuck permanently open.
Key Test	Measuring vacuum at the EGR valve or using a scan tool to command the valve open/closed.
Related Issue	Carbon buildup blocking the EGR tube or intake manifold passages.

[LeDaniela]

From my experience turning wrenches, a bad EGR can definitely leave you stranded. If it's stuck wide open, it's like the engine is trying to start while choking on its own exhaust. You'll hear the starter working hard, but it just won't catch. I've seen it more often in higher-mileage cars where carbon buildup is a real problem. It's not the first thing I'd check for a no-start, but if the battery and starter are good, it moves up the list quickly.

[Larry]

It happened to my old truck last year. It started with a rough shake at idle for a few weeks, and then one morning it just wouldn't start. The mechanic said the EGR valve was seized open, flooding the cylinders with exhaust gas and preventing combustion. It was a relatively straightforward fix. The key takeaway is that a no-start from a failed EGR valve usually gives you some warning signs, like poor performance, before it strands you completely.