Auto Diagly

Engine stalling can happen at idle, while driving, during braking, or when shifting. Each scenario points to different root causes. This guide cuts through theory and delivers actionable diagnostics, repair steps, and expert insights to help…

When your car suddenly drinks more gas, it’s not just a wallet problem—it’s a symptom. As a master mechanic with decades in the bay, I’ve seen every cause from a $5 vacuum hose to internal engine…

In my two decades as a shop foreman, few components have caused as much confusion—and avoidable comebacks—as the humble PCV valve. It’s small, inexpensive, and often overlooked, but when it fails, the symptoms can mimic serious…

Hard cold starting in diesel engines is a common frustration, especially when winter hits. As a senior automotive editor and master mechanic, I’ve seen countless owners replace expensive parts without fixing the real issue. The key…

In my 20+ years as a shop foreman, I’ve seen more engines compromised by overheating than just about any other single issue. It’s not just about the temperature gauge climbing—it’s what happens beneath the surface when…

A clogged or failed PCV (Positive Crankcase Ventilation) valve is one of the most preventable yet damaging engine issues I see in the shop. It often starts silently but can lead to oil leaks, poor performance,…

In my 20+ years turning wrenches in independent shops and dealerships, the turbocharger has gone from a high-performance novelty to a standard component on everything from compact sedans to full-size pickups. With that ubiquity comes a…

In my two decades as a shop foreman, I’ve seen more than a few oil leaks traced back to the front crankshaft seal. While it may seem like a simple component, its failure can stem from…

In my shop, rear main seal leaks come through the door more often than you’d think — especially on higher-mileage engines or those that have seen repeated thermal cycling. While it’s tempting to jump straight to…

Over two decades in the bay, I’ve seen more than a few panic-stricken owners roll in with a temperature gauge stuck at cold or pegged at hot. The instinctive reaction? “Replace the thermostat” or “swap the…

Replacing a turbocharger is a major repair that can cost anywhere from $1,000 to over $4,000, depending on your vehicle and choices made during the repair. As a master mechanic, I’ve seen too many owners pay…

Ignition coil replacement is one of the most common repairs I see on vehicles with over 100,000 miles. The cost varies dramatically—from $70 to over $1,200—not because of the symptom, but due to engine layout, labor…

Loss of turbo boost robs your engine of power, hurts fuel economy, and can lead to long-term damage if ignored. As a senior automotive editor and master mechanic, I’ve diagnosed hundreds of underboost cases—from simple hose…

In my shop, I’ve seen more than a few engines stranded by a tiny component most folks don’t even know exists—the crankshaft position sensor (CKP). It’s not flashy, but when it fails, the engine often won’t…

Intercooler problems often masquerade as turbo, fuel, or sensor failures. As a master mechanic, I’ve seen too many shops replace expensive components without checking the charge air path. This guide cuts through the noise with real-world…

In my two decades turning wrenches in heavy-duty shops and independent bays, I’ve seen more than a few engines come in with misdiagnosed fuel system issues—especially when it comes to injectors. The confusion often starts with…

A flashing Check Engine Light (CEL) means your engine is actively misfiring, and unburned fuel is entering the exhaust system. This can overheat and destroy the catalytic converter—fast. Unlike a steady CEL, a flashing one demands…

In my years as a shop foreman, I’ve seen more than a few engines come in with vague performance complaints that trace back to the knock sensor. It’s not always the first thing a tech checks,…

In my shop, I’ve seen everything from a faint oil sheen on a pan to puddles big enough to drown a squirrel. The truth is, not all oil pan gasket leaks are created equal. As someone…

Testing spark plug wires properly means combining safety, visual checks, electrical testing, and dynamic evaluation. Misfires, rough idle, and poor fuel economy often trace back to failing wires. This guide gives you the exact steps I…

In my 20 years as a master mechanic, I’ve seen more breakdowns, near-misses, and costly secondary damage tied to failing crankshaft position sensors (CPS) than almost any other single sensor. While some drivers report “limping along”…

Choosing the right spark plug isn’t just about price or marketing claims—it’s about matching the electrode material to your engine’s design, ignition system, and maintenance goals. The three main types—copper, platinum, and iridium—each have distinct strengths…

Getting oil changes right is the single most effective way to extend engine life. As a master mechanic with over 20 years in the shop, I’ve seen engines last 300,000 miles on factory oil—and others fail…

Knock sensor failure can trigger poor performance, check engine lights, and even engine damage if ignored. As a master technician, I’ve seen hundreds of misdiagnosed cases—often from overlooking simple wiring issues or installation errors. This guide…

In my two decades turning wrenches in performance shops, few sounds raise an eyebrow faster than a supercharger making noise. That high-pitched whine? Some folks call it music. But when it changes—gets louder, turns into a…

Yes, a faulty crankshaft position sensor (CKP) can prevent an engine from starting — especially on modern fuel-injected vehicles. When the sensor fails completely, the engine control module (ECM) receives no signal indicating crankshaft position or…

When a turbocharged vehicle develops a whistle, unusual noise, or oil leak, many assume the turbo itself is doomed. But in my 20 years as a master technician, I’ve found that turbos are often misdiagnosed and…

An intercooler is a critical component in turbocharged and supercharged engines, but many car owners don’t fully understand its role—until performance drops or engine issues arise. As a master mechanic with 20 years in performance and…

In my shop, one of the most common calls I get isn’t about rough idling or power loss. It’s: “The check engine light came on, but the car drives perfectly.” That doesn’t mean there’s no problem.…

Disconnecting the EGR valve might seem like a quick fix for rough idle or a Check Engine Light, but it triggers a chain reaction that harms performance, emissions, fuel economy, and long-term engine health. This guide…

Over two decades in the shop, rear main seal leaks have been one of those jobs that look simple on paper but can quickly become a deep dive—especially when you’re under the vehicle and realize how…

In my experience across two decades of heavy-duty and light-duty diesel work, the injection pump remains one of the most critical—and often misunderstood—components in the fuel system. When problems arise, it’s tempting to blame the pump…

In my shop, oil weeping around the valve cover is one of the most frequent complaints I hear from both customers and junior techs. It’s easy to jump to conclusions—many assume it’s just a worn gasket…

In my shop, these kinds of drive-in emergencies make up a good chunk of the first calls we get each morning. The engine turns over but won’t start, fires briefly then dies, or cranks and cranks…

Engine decoking restores performance by removing carbon deposits that disrupt airflow, combustion, and valve operation—especially in direct-injected engines. This guide walks you through real-world diagnostics, proven decoking methods, and critical post-service steps. If your engine hesitates,…

In my shop, I’ve seen DTCs lead to a quick fix and also send technicians down a three-day diagnostic rabbit hole. The difference? Understanding that codes are clues, not confessions. Over two decades, I’ve learned that…

Yes, faulty spark plugs are one of the most common causes of engine misfires. After two decades as a master mechanic in both independent shops and dealerships, I’ve seen countless misfires traced back to worn, fouled,…

In my shop over the last two decades, few issues have caused more misdiagnoses than boost pressure problems. Turbocharged and supercharged engines rely on precise airflow, and when boost drops, power suffers. The instinct is often…

Replacing engine mounts is a common repair that can range from a straightforward DIY job to a complex, shop-intensive task. The total cost depends on your vehicle, the type of mounts, labor accessibility, and whether additional…

Oxygen sensors are critical to engine performance, but they often fail prematurely due to preventable causes. As a master mechanic, I see countless technicians replace sensors without diagnosing the root issue—leading to repeat failures and wasted…