might be bad motor mount / or electrical short
A car might stall when shifting from park to reverse if the idle is set too low. It is also possible that the engine stalls because it is not fully warmed up before shifting from park to reverse.
Bad clutching? Idle adjustment
your fuel pump can be broken or your fuel injectors...
Probably needs a new Idle speed sensor
Engine idle too high.
The increased idle when started is normal, all properly working cars that aren't ancient will do it. As far as the hard shift goes, your tranny.
No! it only controls the air/fuel mixture at idle - it is by-passed when the engine revs-up. Generally, when there is a problem with the air control valve it causes the idle to become erratic and 'hunt' and maybe the engine keeps stalling.
An erratic idle with air conditioning (AC) engaged can occur due to several reasons. The additional load from the AC compressor can strain the engine, causing fluctuations in RPM if the idle speed is not properly adjusted. Other potential causes include vacuum leaks, a dirty or malfunctioning idle air control valve, or issues with the engine management system affecting fuel delivery and air intake. Regular maintenance and diagnostic checks can help identify and resolve these issues.
Bad powertrain mount or worn CV joint or high idle speed or torque converter problem.
Unlikely. A faulty IAC will give you poor, erratic idle speed.
If your idle speed is adjusted properly (not too high), yet you can visibly see fuel entering the venturi, it may be because of check balls sticking within the circuits that aren't supposed to be working at idle, or internal gaskets leaking, or more often, a problem with the float level, which causes fuel to "spill" over the top, in an uncontrolled fashion. This causes CO levels at idle to skyrocket, which in turn will tax the catalytic converter (if equipped). This spilling is usually accompanied by an erratic "spitting" sound, and may cause erratic idle speeds as well. The cure for such a condition is inevitably a carb overhaul for best results.
Air Leak or hose has come off from MAP sensor