Symptoms
With the wide range of possibilities, the listed problems may or may not be present. However, this is where it is important to pay close attention to the observed symptoms and note what and when symptoms appear for the diagnostic strategy.
- Vehicle misfires at idle
- Hard to start, especially when hot
- Very irregular idle
- Additional codes to identify the cause of the original P2187 code
- Hissing noises
- Lower turbo boost numbers
- Fuel smell
Potential Causes of P2187 DTC
- Faulty O2 sensor (front)
- Faulty fuel cap seal
- Leaking or loose oil filler cap
- Air leak in the intake manifold downstream of the mass air flow sensor due to the manifold itself, disconnected or cracked vacuum hoses, leaking MAP sensor, leak at the turbo bypass or it is stuck open, brake booster hose, or a leak in the EVAP system hoses.
- Faulty MAP sensor
- EVAP purge valve
- Fuel injector leak
- Faulty fuel pressure regulator
- Leaks in the exhaust system
Faulty variable camshaft timing - Faulty ECM (engine management computer)
- Faulty O2 heater (front)
- Clogged fuel filter
- Fuel pump wearing out and producing low pressure.
- Faulty mass air flow sensor
Diagnostic Steps / Repair
Your strategy for locating this problem starts with a road test and observing any symptoms. The next step is to use a code scanner (available at any auto parts store) and retrieve all additional codes.
The computer has set a P2187 code indicating that the fuel mixture is lean at idle. This is the main code, however, any faulty component in this loop that has the potential to cause a lean mixture will also be set in the code.
If the road test produces no symptoms, it is possible that this is not a real code. In other words, the fuel mixture is not lean and the computer or the oxygen sensor is responsible for setting the code.
Each vehicle has a minimum of two oxygen sensors – one in front of the catalytic converter and one after the converter. These sensors report the amount of free oxygen remaining in the exhaust gases after ignition, which determines the fuel ratio. The front sensor is primarily responsible for the mixture, the second sensor behind the exhaust is used for comparison with the front sensor to determine if the converter is working properly.
If a rough idle is present or any of the other symptoms, start the process first with the most likely cause. Either unmetered air is entering the intake manifold, or there is a lack of fuel pressure:
- Check the fuel cap for cracks and for seal and function
- Open the hood and make sure the oil filler cap is tight
- If additional codes were present, start by inspecting them first
- Look for air leaks starting from the mass air flow sensor. Check the hose or connection between the sensor and the intake manifold for cracks or loose connections. Check all vacuum hoses properly attached to the intake manifold, including the one from the vacuum brake booster. Check the MAP sensor hose and all turbo hoses, if applicable.
- With the engine running, using a can of carburetor cleaner, spray a fine mist around the base of the intake manifold and where the two halves meet if it is a two-piece unit. Spray around the base of the EGR for leaks into the manifold. The RPM will increase if a leak is found.
- Check the PCV valve and hose for leaks.
- Inspect fuel injectors for external fuel leaks
- Inspect the fuel pressure regulator by removing the vacuum hose and shaking it to see if there is fuel. If so, replace it.
- Stop the engine and install a fuel pressure tester on the Schrader valve on the fuel rail. Start the engine and note the fuel pressure at idle and again at 2500 RPM. Compare these figures with the desired fuel pressure found online for your vehicle. If out of volume or pressure, replace the pump or filter.
- The remaining components must be inspected by a service center equipped with a Tech 2 scanner and programmer.