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Tech Feature: Diagnosing Intermittent Driveability Issues

Intermittent driveability problems of any kind are always a challenge to diagnose. When a customer brings you a vehicle and complains of a stalling problem, you may not have much to go on other than their description of what is happening and when it happens. The more information you can get out of them the better, because you’ll likely need all the details you can get to narrow down the list of possible causes. Many times, there will be no check engine light ….

Tech Feature: Understanding How Wide Ratio Air/Fuel (WRAF) Sensors Work

Instead of giving a simple rich/lean indication, wide ratio air/fuel sensors measure the "actual" air/fuel ratio. A WRAF sensor can measure mixtures that range from extremely rich to extremely lean (even straight air!). This ability allows the PCM to control fuel mixtures much more precisely, to handle much leaner fuel mixtures, to reduce emissions and to improve fuel economy compared to ordinary switching O2 sensors. WRAF sensors react much faster than ordinary O2 sensors, which allows them to ….

Emissions Update: Understanding How Wide Ratio Air/Fuel (WRAF) Sensors Work

Instead of giving a simple rich/lean indication, wide ratio air/fuel sensors measure the “actual” air/fuel ratio. A WRAF sensor can measure mixtures that range from extremely rich to extremely lean (even straight air!). This ability allows the PCM to control fuel mixtures much more precisely, to handle much leaner fuel mixtures, to reduce emissions and

Diagnosing Intermittent Stalling Issues

Intermittent driveability problems of any kind are always a challenge to diagnose. When a customer brings you a vehicle and complains of a stalling problem, you may not have much to go on other than their description of what’s happening and when it happens. The more information you can get out of them the better,

Tech Tip: Diagnosing Intermittent Stalling Issues

Intermittent driveability problems of any kind are always a challenge to diagnose. When a customer brings you a vehicle and complains of a stalling problem, you may not have much to go on other than their description of what is happening and when it happens. The more information you can get out of them the better, because you’ll likely need all the details you can get to narrow down the list of possible causes ….

Tech Tip: Uncovering the Cause of a Burned Piston

My engine burned a piston. What does that mean and why did it happen? Answer: It means the piston failed due to excessive heat in the combustion chamber. A burned piston will typically have a melted appearance, or a hole burned completely through the top of the piston. Aluminum can only withstand so much heat, and when it gets too hot, it melts. The underlying cause is usually detonation and/or ….

‘Sensing’ Problems: A Drop in Fuel Economy and Higher Exhaust Emissions Signal O2 Sensor Replacement

Oxygen sensors have been used for more than a quarter of a century, dating back to 1980 when the first computerized engine control systems appeared. Part of the fuel management system, the oxygen (O2) sensor monitors unburned oxygen in the exhaust. The powertrain control module (PCM) uses this information to determine if the fuel mixture

Oxygen Sensors: Are You Up to Date on the Latest Designs?

If you’re a technician who works on late-model import vehicles and diagnoses engine performance and emissions problems, you probably have a good understanding of how oxygen (O2) sensors work. You know that all late-model engines have at least one or more “upstream” O2 sensors in the exhaust system to monitor the air/fuel mixture, and one

Getting a Fix on Piston Diagnosis and Inspection

Piston failures in late-model engines are relatively uncommon thanks to computerized engine controls that keep a close watch on the air/fuel mixture, and knock sensors that back off spark timing advance if detonation is detected. Pistons are also lasting longer because many engines now come factory-equipped with stronger hypereutectic alloy pistons that can withstand higher

Taking Deep Breaths

I had an interesting one the other day. This was a 2005 Ford F-150 4.6L that was setting fault codes for both banks lean, a P0171 and P0174. This vehicle was a trade-in to a used car lot and had only slightly more than 29,000 miles on it. Where to Begin? Of course, the first