2004 O2 Stuck lean code

C
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Joined
Oct 4, 2023
Thunderbird Year
2004
My 2004 has been getting "o2 sensor 1 stuck lean" codes on both banks, and cannot figure out why. It happened when the car idles. If i dont idle it for a long time and just drive it, goes away (engine light goes back off).

I have no other codes. Im thinking vacuum leak. So I was playing around with my cheapo code reader, and when I ran the evap diagnostic, it says "Evaporative System Leak test failed". I have no evap codes at all.

Im wondering is something like the purge valve or anything else in the evap system could be leaking enough vacuum at idle to make it run lean and give the O2 sensor "stuck lean" codes?
 
I was playing around with my cheapo code reader, and when I ran the evap diagnostic, it says "Evaporative System Leak test failed". I have no evap codes at all.
Buy something like a BlueDriver OBDII reader. The cheap readers don't pull all the information from the car. You can use it for years on various cars, so makes no sense not to have one if you work on your own car.

You can do that or pay 125+ to a shop to diagnose.
 
My 2004 has been getting "o2 sensor 1 stuck lean" codes on both banks, and cannot figure out why. It happened when the car idles. If i dont idle it for a long time and just drive it, goes away (engine light goes back off).

I have no other codes. Im thinking vacuum leak. So I was playing around with my cheapo code reader, and when I ran the evap diagnostic, it says "Evaporative System Leak test failed". I have no evap codes at all.

Im wondering is something like the purge valve or anything else in the evap system could be leaking enough vacuum at idle to make it run lean and give the O2 sensor "stuck lean" codes?
What are the actual code/s? If the gas cap is good do the scan record the codes then do a hard reset and drive the car for 50-75 miles with a few stops. Rescan and record any codes if any. Rescan the car after you drive it and return home a few times . if you think the evap system is leaking a simple smoke test will revile it.
 
What are the actual code/s? If the gas cap is good do the scan record the codes then do a hard reset and drive the car for 50-75 miles with a few stops. Rescan and record any codes if any. Rescan the car after you drive it and return home a few times . if you think the evap system is leaking a simple smoke test will revile it.

yeah Im suspecting evap. in fact, even though the lean codes go away and come back, and seem to happen when I let it idle, I got another clue...

on my cheap scanner there's an evap test function and it says FAIL, even tho no evap codes. my friends shop has a smoke test machine, but he has never used it and doesnt know much about it. Im going to borrow it and try to get it working.
 
yeah Im suspecting evap. in fact, even though the lean codes go away and come back, and seem to happen when I let it idle, I got another clue...

on my cheap scanner there's an evap test function and it says FAIL, even tho no evap codes. my friends shop has a smoke test machine, but he has never used it and doesnt know much about it. Im going to borrow it and try to get it working.
under the hood take off the bottom evap line off the purge valve start the car cold on put your thumb/finger over where the line was removed if you fell any vacuum your valve is bad. also can be a vacuum leak you can make a cheap smoke tester with a cigar and one of those liquid hand transfer pumps (look on you tube)
 
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