1999 Ae110 Corolla Hardstarting When Hot - Toyota Corolla, Chevy Prizm (1998-2008)

I have a 1999 AE110 Corolla with a 5A-FE engine. The engine starts good when cold and runs well. However when its hot, and I switch off for 15 mins, it would hard-start after and then run normally? I was suspecting that I have a dribbling injector, how how can I check for this? Also, I tested the Engine Temperature sensor with an Ohmeter and the readings were within specification. What else could be the culprit for this problem? I also get an idling problem at times when the engine is hot, the rpm drops but the car idles as if it wants to cut off but it doesn't cut off. I cleaned the idle air control valve and throttle body and the problem persists, I also tested the resistance of the IACV and its good. Any gurus on the forum, please provide some assistance! Thanks!

Dribbling fuel injector would have to checked off the car - as if it one is dribbling the other would probably benefit from flow testing and a good cleaning. Sounds like you went over the car pretty thoroughly, we don't have the 5AFE engine over here - but I assume it is pretty close to the 4AFE/7AFE in overall design.

I would suspect a possible vacuum leak somewhere. Vacuum leak would explain the hard starting and poor idle you are seeing. The very nature of some vacuum leaks being intermittent makes some harder to track down. Only happening when the engine is hot, could be a clearance / thermal expansion issue somewhere. Could also be something to do with EGR system, as quite a few vacuum connections are made to that system.

Yes I have exhausted my checks but I will have a closer looks at my vacuum connections. The 5AFE is very similar to the 4AFE with the exception of the displacement, they both carry the same parts/part numbers. I have obtained a second fuel line from the filter to the fuel rail, I was thinking about splicing that line and putting a gauge, running the fuel pump with the ignition on via the diagnostic port and see how the fuel pressure looks....if an injector is dribbling maybe the pressure would fluctuate?

A leaking injector will slowly drop the pressure when you have the car ON but not running - run an inline pressure gauge, start and run car, note the fuel pressures and see if they are within spec for a healthy fuel pump. Then turn off the car and verify if the fuel pressures are steady and holding. If it drops slowly, you have a leaking injector.

A weak fuel pump might also be another possibility for hard starting. Same with a bad igniter coil, the 4AFE engines here will exhibit a hard to start condition after the car has fully warmed up.