* Fuel Injectors: Cold starting issues are often related to fuel injectors. When cold, the injectors might not atomize the fuel properly, leading to a poor mixture. The starting fluid compensates by providing a highly flammable mixture. Injectors can get clogged, stick, or have low pressure. This is a very common cause of hard cold starts.
* Throttle Position Sensor (TPS): A faulty TPS can give the engine computer inaccurate information about the throttle position, leading to improper fuel delivery, especially during cold starts when the computer relies more on sensors to establish the initial fuel mixture.
* Mass Airflow Sensor (MAF): Similar to the TPS, a dirty or faulty MAF sensor provides incorrect air flow data to the computer, affecting the fuel mixture calculation. This is more likely to cause issues across temperatures, but a particularly dirty sensor *might* be worse when cold.
* Crankshaft Position Sensor (CKP): While less likely, a failing CKP sensor can cause starting issues, particularly when cold. The sensor tells the computer the crankshaft's position to time the ignition precisely. A weak signal when cold could disrupt this timing.
* Ignition System (Less Likely): While starting fluid bypasses the fuel system, if the spark isn't strong enough when cold, this could be a contributing factor. Check your spark plugs, wires, distributor cap and rotor (if applicable). A weak coil could also be a suspect.
Why not the fuel pump (likely)?
A failing fuel pump usually leads to consistent starting problems, not just when cold. The pump pushes fuel, and a weak pump will have trouble pushing it regardless of the engine's temperature. If it was the fuel pump, you'd likely struggle to start it even when warm.
Troubleshooting Steps:
1. Check for fuel pressure: This is crucial. You need a fuel pressure gauge to measure the pressure at the fuel rail. Compare the reading to the specifications in your repair manual. Low pressure points to fuel pump or other fuel delivery issues.
2. Inspect fuel injectors: A visual inspection might reveal obvious clogs or damage. A more thorough check might involve testing the injectors' spray pattern and resistance.
3. Clean or replace the MAF and TPS sensors: These are relatively inexpensive parts and are often easily cleaned (with MAF sensor cleaner).
4. Check for vacuum leaks: A significant vacuum leak can disrupt the engine's air/fuel mixture, especially during cold starts.
5. Inspect spark plugs and ignition components: Check the condition of your spark plugs and wires for wear or damage.
In short: Starting fluid temporarily solves the fuel delivery problem, so focus your efforts on the components in the fuel system *after* the fuel pump. Fuel injectors and sensors are prime suspects for cold-start issues. Getting a fuel pressure test is your first step. A mechanic with experience in older vehicles can diagnose this more quickly.
