Q: 2003 buick century (3100 engine) is hard to start

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2003 buick century (3100 engine) is hard to start when hot. When cold starts ok. Fuel pressure at schrader port is 26 psi running engine. P0171 code lean bank 1, generated with check engine light on. Changed fuel regulator, air filter, MAF sensor, O2 sensor, and the fuel filter. Checked for holes on air intake hose between the filter and carb. Checked for vacuum leaks visually and with carb cleaner and starting fluid - none - no rise in rpm's.I removed the power from Throttle position sensor, maf sensor, idle control sensor and the car still ran fine - did not stall, slight change in rpm. When I squirt starting fluid into vacuum tube hole on air intake hose to carb, the car will start. Could it be the fuel pump going bad? What pressure should I read at the schrader port?

My car has 100000 miles.
My car has an automatic transmission.

I would recommend having your vacuum levels checked with a vacuum gauge. This can be done by removing the vacuum hose from the brake booster and inserting the hose of a vacuum gauge. This will tell you if the engines vacuum levels are up to spec. You want to have at least 20 inhg. If your vacuum levels are lower than 20 inhg then you likely have a vacuum leak. If a vacuum leak is discovered, I would recommend having a smoke test performed on your vehicle to determine where the leak source is. This smoke test will introduce smoke into your vehicle’s intake system and release the smoke whereever the leak is .

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