1997 Bonneville SE, service engine light on

ShellyWest

My 1997 Bonneville SE service engine light is on. Code reader said P0171. She doesn’t idle or run rough, she runs smooth. This is my first car so it’s a big deal! MAF sensor, leak in air intake manifold?? Help!

imidazol97

Start with the simplest.

Check all the rubber hoses on the engine for dry rot/hardening and cracks in them. IIRC that was a problem on the 1998 lesabre I had--same car as yours.

Check the big hose on the back of the engine that goes to the power brake booster for cracking The tubes from the vacuum go into a bundle and across to the passenger side where there's a T in the lines. Before the T, there's a one-way valve. I believe the lines around there are rubber again.

From the T, one line goes inside the car and the other line goes toward the front to a vacuum storage tank in front of the tire under the headlight. Look up from the ground. That tank can crack, but I dont' know if it would leak enough air to upset the engine lean/rich trim. If it's cracked, your vacuum controlling the AC/heat doors might act strange at times.

The upper plastic intake manifolds have cracked, and some have found leaks around the edges because of loose bolts or warping. Spray carb cleaner around the edges with the engine running. If it's sucked in, the engine will change its idle.