Owner's Problem Description
The owner reports that after replacing the valve cover gaskets, oil was discovered near the spark plugs, leading to their replacement as well. Now, when starting the car in the morning, it fails to start completely, requiring the engine to be revved for about 45 seconds before it runs smoothly. Once started, the vehicle operates normally throughout the day. This issue only occurs on the first start of the day.
Professional Technical Analysis
This 2001 Mitsubishi Galant, likely equipped with a 2.4L 4-cylinder engine and around 120,000 miles, exhibits intermittent starting issues primarily during the first start of the day. The symptoms suggest potential fuel delivery problems or air-fuel mixture issues, particularly after the recent valve cover gasket replacement. The vehicle's fuel pressure should be verified, as the owner noted rough running and increased fuel consumption, which can indicate inadequate pressure at startup. An expected fuel pressure range for this vehicle is 30-40 PSI. A significant drop in pressure could lead to starting difficulties, necessitating a check of the fuel pump and fuel filter for clogs or failures. The spark plugs should also be verified against OEM specifications (Mitsubishi P/N MD346285), ensuring correct type and gap. If the plugs are incorrect, it could lead to misfiring and poor performance. Additionally, the idle air control valve (IAC) should be inspected for functionality, as a malfunctioning IAC can prevent proper idle during cold starts, contributing to the rough running condition. Current observations indicate that the vehicle runs smoothly once started, but the initial starting issue raises safety concerns, especially in cold weather. The interconnected systems of fuel delivery and ignition timing must be thoroughly assessed, as any inconsistencies could cascade into further complications.
Possible Causes
Most common causes (ordered by frequency):
- Fuel Pressure Drop: The vehicle may not be maintaining adequate fuel pressure at startup, particularly if the fuel pump is failing or the fuel filter is clogged. A proper fuel pressure range is 30-40 PSI. If the pressure drops too quickly, it could lead to hard starting and poor initial performance. Fuel pressure should be tested before starting the vehicle using a gauge attached to the Schrader valve on the fuel rail. - Rough running, increased fuel consumption, possible fuel pressure gauge reading below spec.
- Incorrect Spark Plug Installation: If the spark plugs were not replaced with the correct type or gap, it could lead to misfiring or poor ignition. The correct spark plug for this vehicle is Mitsubishi P/N MD346285. Ensure the gap is set to manufacturer's specifications, typically around 0.044 inches. - Poor idle quality, potential misfiring under load, increased fuel consumption noted.
- Idle Air Control Valve (IAC) Failure: A malfunctioning IAC can cause rough idling and poor starting, especially when the engine is cold. The IAC regulates airflow during idle and can affect how the vehicle starts. Testing should include checking the IAC for proper operation and cleaning if necessary. - Rough idle when cold, improved performance once warmed up, potential codes related to IAC.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Initial OBD-II Scan: Begin with a thorough scan using an OBD-II scanner or the GeekOBD APP to retrieve any stored fault codes, especially related to the ignition system or fuel delivery. Note any freeze frame data that could indicate conditions during previous failures.
- STEP 2 - Fuel Pressure Testing: Attach a fuel pressure gauge to the fuel rail's Schrader valve and measure the fuel pressure during key-on and cranking conditions. Ensure the pressure remains within the expected range of 30-40 PSI. A significant drop could indicate a failing pump or clogged filter.
- STEP 3 - Spark Plug Inspection: Remove the spark plugs and inspect them for proper type and gap as per Mitsubishi specifications. Check for signs of fouling or wear, and replace with OEM plugs if necessary. Ensure the gap is set to approximately 0.044 inches.
- STEP 4 - IAC Functionality Check: Test the idle air control valve for proper operation by observing its response in live data. Check for any stored codes related to IAC function and clean or replace as necessary to restore proper idle control.
