Hello,
About 3 weeks ago, my check engine light went on with a P0171. Its been very cold here and the car would stumble on first startup. Once the car warms up, its fine. I also had a faint smell of gas.
Thanks to this forum, I saw some possilbe causes of P0171. From dirty MAF sensor, dirty fuel injectors, bad spark plugs,etc..
I cleaned the MAF with brake cleaner. Didn't work. Used a bottle of fuel injector. Didn't work. I knew the spark plugs were still good since I replaced them about 10K miles ago and the issue only happened in winter months.
So I replaced the intake manifold gasket and that fixed my idling problem and check engine light. I had to do the install 2x. The first time, I disconnected a vacuum hose under the throttle body without knowing it. It happened while pulling the intake manifold out and leaving it in a vertical position. When I started the car, it hesitated like crazy and the brake pedal was very hard to depress. After 1 minute of idle, the car would die. Plugged the OBDII reader fthat I rented rom Autozone and codes were P0300, P0301, P0303 and P0304 (misfire).
I took it apart again and that's when I noticed the vacuum hose under the throttle body was disconnected (no wonder it was hard to pull the manifold the first time
). I also took this time to clean the throttle body with a tooth brush and manifold with an intake cleaner.
The car no longer stumble on first startup and idle doesn't spike to 1500-2000k on cold weather.
Just thought I'd share my experience.
This forum rocks!!
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