Category Archives: EJ25

Knock Sensor diagnosis for Subaru

Knock Sensor diagnosis for Subaru:

This is a simple overview on diagnosing knock sensor issues with your Subaru Impreza/Forester/Legacy/Etc.

The knock sensor is designed to sense knocking signals from each cylinder. The knock sensor is a piezo-electric type element which converts knocking vibrations into electrical signals.
The knock sensor is designed to sense knocking signals from each cylinder. The knock sensor is a piezo-electric type element which converts knocking vibrations into electrical signals.

The knock sensor is designed to sense knocking signals from each cylinder. The knock sensor is a piezo-electric type element which converts knocking vibrations into electrical signals. The electrical signal is sent to the ECM, which changes the ignition timing to reduce the engine knock or ping. For this system to work correctly, the knock sensor must first hear the engine ping. The driver of the vehicle may also hear a small engine ping. A delay of approximately 1-2 seconds is normal, depending on the fuel quality, engine load, air temp, etc. At this time, the ECM will retard the timing.

This function can be viewed on the Select Monitor RTRD mode. When the knock is eliminated, the timing is gradually advanced to the specified setting. If engine ping is heard again this process is repeated. This will continue until the knock sensor no longer hears the engine knock or ping.

Note: This is a normal operation of the knock sensor. Do not try to repair it.

The next page will discuss asking the right questions on diagnosing knock sensor failures.

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Engine noise when cold (Winter is coming)

Engine Noise When Cold:

Beginning with the 1997 model year, the 2.2 and 2.5 engines were made more fuel efficient, more powerful, and were given a flatter, more usable torque curve than in previous years. To achieve these objectives, it was necessary to make improvements and modifications to the Subaru engine lineup. The following are some of those improvements:

• Mechanical valve lash adjusters (reduces friction).
• Lightweight pistons (reduces inertia).
• Short skirt, Molybdenum coated pistons (reduces friction).
• Increased compression ratio (improved power output).
• Improved cylinder head design (improved cooling).
• Improved induction system (improved breathing).

Engine Noise when cold: As a result of these enhancements, some Subaru engines may exhibit some engine noise during the warm-up period after a cold startup.
Engine Noise when cold: As a result of these enhancements, some Subaru engines may exhibit some engine noise during the warm-up period after a cold startup.

As a result of these enhancements, some Subaru engines may exhibit some engine noise during the warm-up period after a cold startup. This engine noise is a consequence of the engine improvements and is not, in any way, an indication of any engine problem.

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Subaru Engine Block Piston Size Identifier:

Subaru Engine Block Piston Size Identifier:

The picture below of this paragraph shows the location of piston size and main journal size information on all Subaru engines. As the figure illustrates, it is possible to have more than one piston size in the same engine.

Subaru Engine Block Piston Size Identifier: The picture on the bottom shows the location of piston size and main journal size information on all Subaru engines. As the figure illustrates, it is possible to have more than one piston size in the same engine.
Subaru Engine Block Piston Size Identifier:
The picture on the bottom shows the location of piston size and main journal size information on all Subaru engines. As the figure illustrates, it is possible to have more than one piston size in the same engine.
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Valve Adjustment DOHC Engine Part 2

Valve Adjustment Tool and
Adjustment Procedures:

As we mentioned, it takes a special tool to work within the limited clearance area between the cylinder heads and the frame rails. The ST 498187 is a three part tool. One part wraps around the cam lobes, a second touches the outer edges of two shim buckets, and a third eccentric bolt exerts the necessary pressure to push a pair of shim buckets away from the cam lobe to make shim removal and replacement possible.

The tool installed in the three steps:

• Wrap the first half of the tool (part A) around the lobes.
• Attach the second half (part B) to part A by sliding its pins through the slotted holes in part A.
• Install the eccentric bolt (part C) into the hole in part A.

Valve Adjustment Tool and Adjustment Procedures: As we mentioned, it takes a special tool to work within the limited clearance area between the cylinder heads and the frame rails.
Valve Adjustment Tool and Adjustment Procedures: As we mentioned, it takes a special tool to work within the limited clearance area between the cylinder heads and the frame rails.

The eccentric bolt forces parts A and B away from one another. Because part A can’t move (it’s wedged against the cam lobes), the only thing that can move is part B. Part B moves by forcing the shim buckets downward, away from the camshaft.

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Valve Adjustment DOHC Engine

Valve Adjustment DOHC 2.5 Liter Engine:

The first versions of the 2.5 liter twin cam engines employed non-hydraulic valve actuation. Like the timing belt, the clearance between the engine valves and the shim and bucket valve actuators does not require inspection and/or adjustment until 105,000 miles have elapsed. However, various circumstances may require an adjustment before that milestone is reached.

 Valve Adjustment: Unlike some overhead cam engines that require you to rotate the cam until each cam lobe is facing 180 degrees away from the adjustment shim, Subaru has very specific procedures for adjusting four valves at a time (a pair of intakes and a pair of exhausts).
Valve Adjustment: Unlike some overhead cam engines that require you to rotate the cam until each cam lobe is facing 180 degrees away from the adjustment shim, Subaru has very specific procedures for adjusting four valves at a time (a pair of intakes and a pair of exhausts).

Clearance is tight and there is little room to work between the cylinder heads and the left and right frame rails. A special tool (ST 49818700) is available for depressing the valves and removing the adjusting shims. Without this tool, the job is impossible to accomplish with the engine in the car. Once again, we had the benefit of working on an engine that had already been removed from the car. Before you can adjust the valves, the engine must be cold. Consult the service manual to determine the parts that will need to be moved or removed to make some room to work.

Unlike some overhead cam engines that require you to rotate the cam until each cam lobe is facing 180 degrees away from the adjustment shim, Subaru has very specific procedures for adjusting four valves at a time (a pair of intakes and a pair of exhausts). The pairs of intakes and exhausts are never for the same cylinder, which makes things rather interesting. This system requires you to turn the crankshaft a total of four times to complete the adjustment procedure.

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Boost control systems on a Turbo Subaru:

Boost control system on a Turbo Subaru:

This guide covers most  boost related issues including a short introduction on how your boost systems work. This information is based on the Classic Impreza’s, but will cover the newer WRX/STi cars to a certain extent.

Safe boost levels:

When modding your car without mapping (full de-cat and high flow induction etc) you increase the efficiency of your turbo which could result in engine damage due to lean running at high rpm / max boost. To prevent damage always try and keep your boost level as close to standard as possible until your car is mapped for the increase in boost pressure.

TLDR: Don’t screw with your boost levels until you get the car tuned by someone who knows what they are doing. Otherwise you’ll probably end up with a blown up Subaru.

Boost Issues:

Is the boost control system connected correctly:

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Alternator Replacement Subaru WRX/STi:

Alternator Replacement Subaru WRX/STi:

This is a step by step guide in replacing a alternator on a EJ series engine on a 02-07 Subaru WRX/STi.

Alternator Replacement Subaru WRX/STi: The Alternator cover needs to be removed.
Alternator Replacement Subaru WRX/STi: The Alternator cover needs to be removed.

1.) Open up the hood and disconnect the battery. Note: This is important. If you fail to disconnect the battery, you will be grounding out your tools and making all sort of popping noises and sparks. It can destroy your electrical system. So ensure that your battery is disconnected. It’s best to just remove the battery itself from the car.

2.) Take the plastic cover off that sits over the belts on the front of the EJ series engine. There are a couple of 10mm bolts. The bolts are pretty easy to get off. On your WRX and STi there is also some clips that will come off. The best way to get them off the cover is to use a needle nose pliers on the bottom side to undo the clips.

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Maintenance:Subaru Periodic Maintenance Part 3:

Maintenance: Subaru Periodic Vehicle Maintenance Services:

Brake Fluid:

Many late model Subaru vehicles are equipped with ABS braking systems. The added complexity of these systems provides an additional incentive for following the recommended brake fluid replacement interval of 30 months or 30,000 miles. Brake fluid accumulates water and other contaminants over time. These contaminants can attack the internal parts of the brake system, compromising its performance and possibly causing brake failure.

Maintenance: Subaru Periodic Vehicle Maintenance Services: Make sure to replace brake fluid at least every 30 months of 30,000 miles. At least once a year if the Subaru sees heavy track use.
Maintenance: Subaru Periodic Vehicle Maintenance Services: Make sure to replace brake fluid at least every 30 months of 30,000 miles. At least once a year if the Subaru sees heavy track use.

The brake master cylinder has a semi-transparent reservoir, making it possible to check the fluid level without removing the reservoir cover. This minimizes the exposure to outside air and limits the amount of moisture that can reach the brake fluid. The fluid level will drop as the brake shoes and pads wear, but the reservoir is large enough to compensate for these changes. If the fluid level is very low, it’s a sure sign the brake pads or shoes are nearly worn out, or there is a leak in the brake system.

Note: When the brake fluid level in the reservoir tank is lower than the specified limit, the brake fluid warning light in the combination meter will come on.

Subaru warns against mixing brake fluids from different manufacturers. Doing so may degrade the quality of the fluid. Only DOT 3 or 4 brake fluid should be used in any Subaru vehicle preferably Subaru brake fluid if you are not going to do a track day build. Consult the service manual for vehicle specific brake bleeding procedures.

Subaru OEM Brake Fluid:

Subaru SOA868V9220 Brake Fluid – 1 Pint

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