Engine Failure

'''With vehicles in the GTA 4 & GTA 5, engines that take a high amount of damage can cause the vehicle to misoperate and decrease it's performance. '''

GTA IV
In Grand Theft Auto IV, if a car was to, for example, take numerous hits at the front-end where the engine is, the car will eventually begin to produce black smoke. From this point, there's a chance of taking light hits, such as even a small bump into another car that will cause the engine to breakdown. If you wanted to repair it, your only option was get out the car, and kick the front of it, like some sort of joke. However, in its delicate state, it had a chance of just going on fire and eventually exploding. Engine failure with helicopters in GTA 4 happened very rarily.

GTA V
In GTA V, engine damage is seen wide-spread from helicopters, cars, planes & jets.

Cars in GTA V
Engine failure remains the same from GTA IV, if a car sustains a high amount of damage for whatever reason, it will begin to smoke black eventually and die. No way seems to be able to be repaired as of so far.

Flying Vehicles in GTA V
Jets, Planes, Helicopters all have engine failure. As similar to cars, if they take damage to their engine's, then they will smoke and black up. However, with flying vehicles, they will take some time to eventually die. With Jets & Planes, a constant beeping sound may occur to alert you of trouble with the vehicle. Jets & Planes are more susceptible to getting their engines damaged, due to their jets being exposed. As seen, for example, on the P-996 Lazer, the engines are exposed in the back, completely susceptible to gunfire and other impact. A common way to experience engine failure, in fact, with the P-996 Lazer, is in an attempt to avoid an oncoming lock-on missle, and it hitting the engine instead of the body of the jet, causing it to blow it up completely.