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Starts great when cold, takes 2-3 seconds after a trip though. Why?

So I put a remote start system in my 2001 Buick Century, which I love do death! But…

The remote start will only push down on the ignition for maybe a second, and if the engine didn’t take off in that amount of time, then the system just turns off the car again and gives up. Now the weird thing is that my car starts just fine in the mornings when it’s cold, or if it has been sitting for more than an hour or so, but if I try to start the car when it has only been off for… let’s say 20 minutes… then it takes about 2-3 seconds of the vrm vrm vrm vrm to get started. Hence, the remote start does not work because it tries to start for a second, then gives up.

I thought it may have been a bad battery, so I put a brand spanking new battery in there… still have the same issue. I replaced the starter motor about six months ago (the “new” one was used though, probably a year old). Alternator is the original. I just barely replaced the intake manifold gasket, water pump, spark plugs, and the fuel filter (installed the remote start at the same time as those things).

Please tell me what I am missing! The only thing left that I can think of is a fuel pump, but it starts just fine if it’s cold. Though i think this is unrelated, sometimes when it is very cold outside and I am braking, the dashboard lights will dim and the heater fan will sound like it is slowing down, but as soon as i take my foot off the brake it usually goes away. It only does this occasionally though, usually when it’s cold outside.

Thank you for your time! I greatly appreciate it!

This sounds like a classic warm start problem. If the cranking sounds at least as robust as when the engine is cold, this is unlikely to be related to the electrical systerm or starter motor. It’s usually a fuel ratio problem. The ECM is supposed to be leaning out the mixture for the coolant and intake air temp. I expect something is a tad askew with this in your car. Ask your mechanic to check the engine coolant temp sensor and the intake air sensor and do a fuel pressure test. That’s probably the place to start. Leaking injectors or problems with the MAF, MAP sensors, throttle body is dirty, the IAC is sticking, or vacuum leaks are also possibilities.

Thank you! You’ve given me a place to start! I appreciate it!