Diagnostic testing on Ford F350.

Diagnostic testing performed on a Ford F350

In Diagnostics by Steves Auto Repair and Tire

The reason behind car problems can’t always be determined at a glance.

To pinpoint some issues, we need to perform diagnostic testing. You can read more about what we do during noise diagnostics in this article we wrote. 

When conducting diagnostic testing, we communicate with the customer about what they’re experiencing and do research on the vehicle and problem. 

Some behaviors our technicians are trying to address, however, only occur in certain circumstances. This can make it more complicated and time consuming to figure out the cause.

How we performed diagnostic testing

One of our technicians experienced this recently when working on a 2008 Ford F350 that came in for an intermittent rough idle. 

It seemed like it was having a misfire on just one cylinder, and it wasn’t happening all the time. After the check engine light came on and we stored some codes, we had a cylinder 4 misfire.

While working on the truck, Brian determined that a fuel injector needed to be replaced.

He was able to confirm this by turning off the injectors one at a time while the truck was running. When the injector for cylinder 4 was turned off, it didn’t make a difference on how well the vehicle operated.

However, it wasn’t malfunctioning continuously. The truck drove fine during the first test drive. When it sat idle for about a minute, it began to run rough and then would become smooth again. 

Because of the amount of time it takes to replace the injectors, it’s best to replace all four injectors on one bank or eight injectors on two banks – even if only one new injector is needed.

Old fuel injectors.
Old fuel injectors

To get to the valve cover and injectors that were located underneath it, Brian needed to remove several components. These included the passenger side valve cover, pump and cooler, coolant bottle and battery.

Technicians also need to replace any coolant and oil that has been lost, and take the vehicle for one or two test drives to make sure it’s working properly.

Make sure to maintain your vehicle

The best thing that you can do to avoid this type of service is to keep up on regular maintenance. This includes making sure the oil is full and clean, and having oil changes performed when your vehicle is due for them.

We recommend having the oil replaced every 3,000 to 5,000 miles.

In some cases, due to age and wear and tire, the injectors may need to be replaced when it reaches 100,000 to 120,000 miles.

The Ford F350 was at around 120,000 miles and we didn’t have history of the injectors ever being replaced.

If you bring your vehicle to an auto repair shop because it’s acting abnormally or making a strange noise, make sure to provide as much information as you can. These details can help the technician narrow down the possibilities, saving you time and money.

Steve’s Auto Repair & Tire is an authorized Goodyear tire dealer located in Woodbridge, Virginia. Automotive repair services are performed on all makes and models, including BMW and Mercedes. Services include oil changes, brakes, alignments, inspections, and computer engine diagnostics.