So when I bought my 99 4runner it had a leaky fuel injector so I replaced the oring. Leak stopped but I’ve been having high idle issues since. The erratic idle stopped but I get a high idle 12-1300 until it’s warms up. It’s running rich, I can tell by smell, and now has the P0171 code. I’ve replaced fuel filter, checked for vacuum leaks, cleaned MAF. I’m about to tear it back down and check that injector and replace all vacuum hoses and gaskets. I bought a scanner and the results of the freeze frame when code triggered are

Load: 13.7%
Coolant temp: 187
Short term fuel: -1.6%
Long term fuel: 37.5%

The high idle at cold start up is normal. Usually when you have a system lean code combined with high fuel trims, rich smelling exhaust, chugging, bad fuel mileage, etc it is a false lean issue causing the ECM to compensate for a non-existent lean condition. Check your O2 sensors

Should I swap 02 sensors?

I battled a mystery check engine light on and off for 2 years then when it shined its ugly head again I got it scanned and turned out it was the downstream O2 sensor. I cleaned the MAF sensor 3 times over a 2 year period, took all the plumbing apart up to the throttle body and cleaned it all out. Now that I replaced it my high idle is gone during start up, and my check engine light hasn't come on since. (knock on wood!). It was also the p0171 code. If it does end up being a bad O2 sensor get the denso OEM number and order it from ebay/rockauto. I paid $50 shipped no tax, and parts stores wanted $100 for the same part.
denso is the OEM manufacturer for toyota sensors/some electronics. Hope you get it figured out.

So, just throwing this out there, I had the 171, and replaced a LOT of shit.

Turned out to be a partially clogged injector.

I bought an injector tester and ultrasonic cleaner off amazon, and haven’t had the code back in 2 years.

YMMV.


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