The Ford Mustang is renowned for its bold styling and brute powerplants, but even these icons experience routine problems. One common issue is a rough, uneven idle stemming from cracked positive crankcase ventilation (PCV) hoses. Damage allows unmetered air to disrupt the air/fuel ratio. This article explores the causes, diagnostics, repairs, and typical costs of remedying rough Mustang idles attributed to degraded PCV system hoses. Getting ahead early keeps your pony galloping properly.
Problem Explanation
The PCV system is responsible for recycling gases from inside the crankcase back into the intake to be burned, rather than venting them directly into the atmosphere. This helps reduce emissions and oil consumption. The PCV hose routes these gases from the valve cover to the intake manifold. Over time, the constant engine vibration, heat cycling, and exposure to oil can cause the PCV hoses to become brittle and develop cracks.
When cracks form in the PCV hoses, unmetered air gets sucked into the engine, creating an uneven air/fuel mixture. This leads to misfires, stumbling, and a rough idle as the engine computer tries to compensate. The idle also tends to get worse as the engine warms up and the PCV system activates. Replacing worn out PCV hoses can often smooth out the idle and restore lost engine performance.
Diagnostic Procedures
Diagnosing a cracked PCV hose requires some basic mechanical tools and hands-on inspection.
Necessary equipment includes:
- Socket set and ratchets for accessory drive belt removal
- Flashlight for illuminating hard to reach areas
- PCV hose removal tool
- Replacement PCV hoses
The main diagnostic steps are:
- Locate the PCV hoses coming off the valve covers – follow them visually to check condition
- Remove accessory drive belt for improved access, if needed
- Inspect PCV hoses closely with flashlight for any cracks, swelling, or blockages
- Wiggle and bend hoses to reveal less visible cracks
- Check hose fittings at valve cover for signs of leaks/seepage
- Determine if original equipment or aftermarket hoses were used previously
- Pressure test hoses if no external cracks are found but rough idle persists
Carefully inspecting all PCV hoses and components can pinpoint if cracked hoses are allowing unmetered air into the Mustang’s engine. Replacing deteriorated hoses is significantly cheaper than replacing valve cover gaskets or intake gaskets due to neglected PCV issues.
Repair Solutions
The main repair for a rough idle from cracked PCV hoses is to replace the degraded hoses. On Mustangs, common problem areas include the PCV hoses running between the valve covers and intake manifold, as well as short crossover tubes between rear valve covers.
Replacement PCV hoses are inexpensive maintenance items available from most auto parts stores or Ford dealerships. Opt for factory Ford hoses or high quality aftermarket hoses designed specifically for Mustangs. Avoid cheap universal fit hoses.
Install new PCV hoses correctly without over tightening clamps. Route hoses away from exhaust components to prevent future cracking. Clear any obstructions, leaks should subside. Be methodical when removing and replacing PCV hoses and connections to avoid dislodging small vacuum hoses nearby that can also impact idle quality if disconnected or blocked.
Performing a proper PCV system hose replacement should eliminate the rough idle in most cases and restore smooth running. No further disassembly of the engine is typically needed for this common Mustang repair.
Ford Mustang Model Years Potentially Impacted
Rough idle from cracked PCV hoses can impact Ford Mustangs across many model years. In particular, Mustang GT models with 4.6L, 5.0L and 5.4L V8 engines tend to develop more crankcase blow-by gases and oil vapor than the base V6 models. More blow-by increases pressure in the PCV system over time, accelerating hose cracking.
The following Mustang model years are most susceptible to PCV hose issues:
- 1996 – 2004 Ford Mustang GT 4.6L V8
- 2005 – 2014 Ford Mustang GT 4.6L/5.0L V8
- 1996 – 1998 Ford Mustang Cobra 4.6L V8
- 1999 – 2004 Ford Mustang Cobra 4.6L supercharged V8
- 2007 – 2014 Shelby GT500 5.4L supercharged V8
Again, high performance Mustang models tend to develop PCV hose problems earlier than base models. But any Mustang beyond 60-70k miles should have its PCV hoses inspected. Catching minor cracks early prevents bigger issues down the road.
Vehicle Components Potentially Affected
- Engine intake manifold
- Cylinder heads
- Engine valve cover gaskets
Cost of Repairing this Issue
Parts cost: $25 – $75 for new PCV hoses
Labor cost: 1.0 – 2.0 hours for R&R at $80 – $120 shop rate
So most Mustang owners can expect to pay $150 – $300 total for PCV hose replacement to cure a rough idle condition. Much cheaper than valve cover gasket or manifold gasket repairs.
John Smith, a Los Angeles-based car specialist and automotive writer, boasts over 20 years in the industry. With a background as a master technician and a decade-long writing stint at notable automotive publications, John now shares his expansive knowledge on CarFinite, simplifying car maintenance for readers.