2002 Dodge Intrepid P0300/P0301: Cold Start Sputtering, Hesitation & Engine Stalling - Diagnosis & Fixes

The symptoms point strongly toward a lean mixture, though not severe enough to trigger lean-specific codes. A vacuum leak is a common cause — especially when the engine runs poorly when cold and improves as it warms up. As the engine heats up, metal components expand and seal small leaks. Start by checking for vacuum leaks using a smoke machine or propane test. Also verify fuel pressure. If both are normal, consider exhaust backpressure issues, which can cause intermittent power loss or hesitation.

On older V6 engines like the 2002 Dodge Intrepid, intake and fuel rail gaskets often fail due to thermal cycling. The bolts in the cylinder head stretch over time, causing gasket blowouts. These leaks are hard to detect with traditional vacuum leak tests because the intake plenum is deep under the engine. A propane tube or smoke machine can help identify leaks at high points under the intake. I’ve never seen a coil failure on this model — it’s more likely a sealing issue than ignition components.

A local shop charged $450 to replace all ignition coils, which I didn’t believe was necessary. I had no way of testing them myself, so I assumed they were recommending a 'shotgun' approach — replacing everything without diagnostics. I won’t return there. I’ve tried resetting the fault at AutoZone and Checker, but both failed — had to disconnect the battery. I’m now planning to test for vacuum leaks. Thanks for the tip — will update on progress.

A simple spark tester from a local parts store is inexpensive and effective. It can visually confirm spark presence and strength. While P0300 and P0301 don’t rule out faulty coils, it’s still worth testing — especially since the issue appears intermittent and cold-start related.

After driving home from work, I had difficulty getting off the curb. Now I have additional codes: P0300, P0301, P132 (O2 Sensor Heater Circuit Malfunction), and P152 (Exhaust Pressure Sensor Issue). Could I have replaced the wrong O2 sensors? I believe I installed both on the engine side of the catalytic converter — which is correct. I suspect a vacuum leak as suggested. My Haynes manual doesn’t list these codes — had to look them up online.

It’s unlikely this is an issue with the 2002 Intrepid itself. Since you replaced the correct O2 sensors, the new codes (P132 and P152) suggest problems with heater circuits or engine-related sensor readings — possibly a faulty signal from the oxygen sensors due to poor grounding or internal failure.

I discussed this with my wife, and she says the car ran perfectly until I took it to Brake Masters. They quoted $600 for replacing the thermostat and coolant hoses — which I disagreed with. I didn’t have them perform any work. It’s strange how such situations can make you question your own judgment. I recently found a worn PCV vacuum elbow and replaced it. Afterward, idling improved slightly, but the engine light came back on. Haven’t checked codes yet.

So are you suspecting Brake Masters caused the issue? Why did you go to them in the first place?

I had a warped left front rotor and was planning to replace it during my vacation. I was too busy for that, so while on vacation, I let them do an oil change and belt replacement. The mechanic called back and said the coolant hoses were collapsing — needed a thermostat. $600. I told him I’d pay that much only if it was truly necessary. I don’t believe they did any damage to the car — just a coincidence. If vacuum leak and fuel pressure tests come up negative, I may take it to a Dodge dealership for professional diagnosis.