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2008 TCH
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694 Posts
Discussion Starter #1
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...
 

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short-throw dipstick
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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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2008 TCH
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694 Posts
Discussion Starter #3
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.
 

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Sounds normal to me. High idle for about a minute or two, then going down to normal after about 4-5 minutes. That's if I start the engine cold and don't touch the gas pedal, just let it idle. If I get in and drive it, the idle settles to about 700-800 rpm after a minute or so.
 
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