Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
hello I have a 1998 Tacoma 2.4 truck. I started getting a po171 code for a long time and I could not figure out the problem. I noticed that the coolant temp was low so I replaced the ect sensor. now the po171 is gone but I'm getting a po130 and po133 code so I replaced the o2 sensor. but still getting the same code. cant find any vacuum leaks and the fuel pressure is 42 pounds at idle. There is no pressure with key on and engine off. not sure if this is normal. Long term fuel trim is around 3 at idle but soon as you press gas it jump to around 25. any ideas on what to check next
Do you have the ability to graph the O2's on a test drive? That'd give you a great starting point as far as identifying what the PCM is seeing on the O2 signal. It'd also be good to look at fuel trims during a steady cruise.
Like Cheryl mentioned, any induction or exhaust leaks are prime suspects in this case. Particularly any exhaust leaks ahead of or near the upstream O2.
Also, this is just a hunch, but we may also want to look at the rear O2. I'm not saying this is a case of downstream fuel control, but I have seen weird cases where the PCM compares the upstream and downstream as part of it's response testing. Short story, it's possible to have a rear O2 that's hanging rich or lean, confusing the PCM's O2 monitor.
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