I think that when the sensor detects it being hot, the IAC increases the amount of air delivered, and the inverse is true when it is cold (giving a richer mix). So if the IAC is closing when hot , essentially starving the chamber of oxygen, the engine wouldn't fire. The other cause of course, could be a lack of fuel.....

I'm guessing that the latter would point towards the fuel pump?

Either way, that would explain why the engine fired and then instantly spluttered until it cut out.

 

Nah - Idle air control does just that, the ECU richens the mixture when required via the fuel injectors, not by altering air volume. The IAC valve operates as a fine-tune on the main throttle valve to account for minor variations and load changes from the alt, a/c and whether the trans is in gear or neutral/park on an auto.

Lack of fuel could be the fuel pressure sensor or the pump, although a pump usually dies and stays dead it can go slightly erratic/intermittent if it has a dead spot as it rotates. Fuel pressure sensor can cause the ECU to kill the fuel pump after a second or so as it acts as a safety precaution in case there is a leak, if it detects not enough pressure it will shut down the pump, a failed sensor can cause that condition - but it should log a code for it.

 

Ok, so after receiving my OBD scanner tool, I have run a scan on the car and there were no faults logged which I found quite interesting. I thought that if it was an electrical sensor that was shutting off air/fuel, there would be some sort of code logged by the ECU.

Now I really am at a loss at to what could be the cause. If the battery has been disconnected and some point, and the idle setup procedure has been ignore, could this cause a rough idle and my problem of it not hot starting?

I'm really clutching at straws tho. Any suggestions are welcome!

 

Just a thought - if the fuel pump relay was faulty, would this throw up a code in the ECU?

After reading the Haynes manual - the section on relieving the fuel line pressure, it says to run the engine then pull the fuel pump relay out. "This will cause the engine to stall as the fuel line will become depressurized". This sounds identical to my problem before I couldn't get the car to restart.

 

I would have thought it would have thrown either a discrete fuel pressure error or at least a "mixture too lean" error as even when the engine stalls the ECU is still powered.

Given the relay is reasonably easy to change though you may as well try it (see if it can be swapped with another non-engine critical one).

 

remove replace the idle air control. worked for me

 

Which obd2 scan tool you used to diagnosis car? I need to know which scanner give accurate results and can read the fault code. I am thinking to buy the Autel al619 scanner https://bestobd2scanners.com/autel/al619-review/. But, I am not sure how good is it! It's price almost 120 bucks and I don't want to spend money on a low-quality scanner.