Oct 22, 2026 at 9:48 PM
Hard starting after the car sits, with good fuel at the rail when you check it, very often comes from fuel pressure bleeding off while the car is parked. The pump builds pressure, but a leaking injector, a leaking pressure regulator, or a check valve in the pump lets it drain away, so the first few cranks spend their time refilling the rail.
Two easy tests:
1. Before cranking, turn the key to RUN for a couple of seconds, back off, and repeat two or three times so the pump primes each time. If it then starts right away, pressure bleed down is your problem.
2. Put a fuel pressure gauge on the rail's test valve, run the engine, shut it off and watch the gauge. Pressure should hold for several minutes. If it drops quickly, one of the parts above is leaking. If your rail has a vacuum operated pressure regulator, pull its vacuum hose: fuel in the hose means the regulator diaphragm is leaking.
Also, since you just oiled the K&N, clean the mass air sensor with MAF cleaner. Filter oil on that sensor is a classic cause of hard starting on these.
The P0136 is the downstream oxygen sensor, the one after the catalytic converter. That sensor mainly monitors the converter, so it is worth fixing, but it is not what makes the car hard to start.
Dana