There’s a lot of aftermarket junk out there.
I suggest you buy an OEM part, to assure it will last.
Yes, an exhaust leak can cause P0420.
Possible, but not the most likely symptom. P0420 means the computer , by reading the pre and post cat sensor signals, thinks the cat isn’t up to the job. Could be caused by the sensors, exhaust leak(s), or the cat is plumb no good. If the latter, one failure mode is the cat is plugged and not allowing a free flow of exhaust. That could cause a hard to start, but would usually also cause the engine to have weak acceleration, loss of engine power. Notice anything like that?
Cranks ok but takes longer than expected to start is usually caused by a fuel rail pressure problem, often the fuel pump check valve is leaking and allowing the fuel in the fuel rail to drain back into the tank. The net result, it takes extra cranking time for the fuel pump to re-pressurize the fuel rail at the next start attempt.
It sounds like I have a bad fuel pump check valve. I don’t think it’s a bad cat. I feel exhaust coming out and there are no bad smells in the exhaust or by the cat. With my OBD2 connector and Torque Lite I thought I could check the fuel pressure however it says “No Data” for fuel pressure. Does the matrix not have a fuel pressure check that goes to the computer? Is there a special PID for it?
I might buy a fuel pressure test kit for my car. There’s one for $28.70 on ebay:
I also see that some people put inline check valves on the gas line instead of replacing the entire fuel pump. I’m not sure about this but I think it could be a quick cheep fix. You can see the gas line coming out by the pump by taking off the back seat and the metal cover. I don’t like messing with gas lines though.
Please let me know your thoughts on putting in an inline check valve by the pump?
If there’s a P0420 code, that indicates that the cat may not be doing its job.
Here’s how to tell.
I’d worry a little about that idea, b/c adding fittings to the fuel path increases chance of external fuel leak, unsafe. Better imo to ask shop to replace fuel pump if you think that’s the problem. Before replacng pump, shop could do a fuel pressure hold test to confirm that’s the likely problem.
NO experience testing fuel pressure on modern car designs. I tested it on my late 70’s VW Rabbit, using a home-brew fuel pressure kit. I had to buy the required fittings separately, connect them to special metal-braided fuel hose. I had a repair book (How to Keep your Rabbit Alive For the Compleat Idiot) that explained how to do it. I fit the description … lol …