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Q: Rich, high idle, odd shifts

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My truck is idling really high...it runs fine til it's warmed up...it no longer does the closed loop warm up and is running really rich so I'm starting to think it might be o2 related...I've changed tps, iac, ect, and cleaned egr. No hose leaks that I can see. But shifts weird. It almost drops first or second it's hard to tell...all I know is it's aggravating because I've changed and fixed almost everything I can and still have the same result. The only way I can get it to run somewhat right at idle is with iac unplugged...I've tried two new ones and the old and the same thing happpens. So it's something I'm missing.

My car has 253000 miles.
My car has an automatic transmission. It also won't go into overdrive. Just recently.

If the truck runs normal at idle with the iac unplugged this would suggest you have a bad O2 sensor especially if you’ve confirmed the same running condition with two different iac sensors. I would recommend having a mechanic from YourMechanic come to your home to hook the truck up to a scanner to confirm this is the case before replacing additional parts that may not be needed.

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