Yoyo

Hey guys my truck say system to lean I have changed maf I'm hearing bad cat or bad 02 sensor but it dont miss and idle funny constantly does it mainly when cool it warms up and does pretty good it just has got to where it will do it while warm but doesnt do it much if sensor was bad wouldn't it do it constantly

 

^Could be vacuum leak, from a cracked hose or bad intake manifold gasket. If visual inspection doesn't show anything obvious, you'll need to hook up a scan tool with live data showing ST and LT fuel trim, MAF reading, and O2 sensor readings at idle and with throttle, and go from there. Is the engine running in open-loop or closed-loop mode when the fault happens?

Do you know how to make a smoke jar for checking vacuum leaks?

 

I haven't found any hoses leaking how can I tell if its manifold gasket

 

^You pipe in smoke through one of the hoses (like the brake booster) and see where it leaks from. Do you know how to make a smoke jar?



Pro mechanics have machines that generate smoke, like this:

$70 AutoLine Pro Automotive Smoke Machine Leak Detector EVAP Vacuum Diagnostics Tester | Economy Series

https://www.amazon.com/AutoLine-Pro-Automotive-Diagnostic-SMK-1/dp/B06XHRBKTM/