P0171 bank 1 lean - Toyota Nation Forum : Toyota Car and Truck Forums
Tacoma 1st Generation (1995.5–2004) 1st generation Tacoma information and discussion.

 
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post #1 of 3 Old 06-10-2019, 05:56 PM Thread Starter
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P0171 bank 1 lean

Truck in sig. So, I have had this code now for about a year. "P0171 bank 1 lean". I cleared it once and a few days later it came back (this was about 8 months ago).


Yesterday I took it upon myself to try and figure out if it was a MAF or O2 sensor problem. I pulled the MAF out, looked for leaks, check vacuum lines, checked for cracked filter box, etc. None found and airbox is only a couple years old, so I knew it was not that.



Anyway... So, after cleaning the MAF, getting everything back together and clearing the code again, the truck runs much better and the light has not come back on this time. However, now when the truck is cold (first start of the day) the RPM's stay at a high idle for a long time at around 1400 RPM. I don't remember it ever doing this before? Is this normal? Once I put in in gear and drive off after only a minute or so everything is normal and idle is down where it normally is at around 700 RPM if I stop and put it in Park again.


Any thoughts? Or normal operation? The check engine light has been on for so long I have forgotten these little things. I still can't believe how much better it runs...

2008 TCH Magnetic Grey on Black
280,000 miles

1999 Tacoma Prerunner SR5 V6/auto White on Oak
235,000 miles
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post #2 of 3 Old 06-10-2019, 06:23 PM
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I think that's unrelated. Do you have a 5VZ?

After a minute of warm-up from cold, try whacking the IAC with some pipe. If the idle drops, the IAC is sticking. 5VZ IAC have that problem, they wear and the shaft goes eccentric.

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post #3 of 3 Old 06-12-2019, 06:51 PM Thread Starter
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It's the 3.4 ltr. I'll give that try. Thanks for the info.


I have noticed over the past day or so, the RPM's settle into a 1200 RPM high idle and after about 1 minute the RPM's are dropping down to normal again.

2008 TCH Magnetic Grey on Black
280,000 miles

1999 Tacoma Prerunner SR5 V6/auto White on Oak
235,000 miles
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