Hard to restart after it warms up

no car told maker or model or engine size.
there are lots causes that, hard starts
if spark good and strong and even HV spark wire sets fresh.
the short list.

1. bad fuel
2. too much fuel cranked and floods
3. IAC bad, idle air valve stuck and wants to flood cold.
4. cold idle is the big clue, where too low. IAC failing
5. EGR sticking open at idle. possible.
6. if you press gas Pedal, at 5% (about) and starts easy and likes that until it worms up that means the IAC is dead.
7. I stop here lots more, no car told.

all cars modern EFI is it EFI> have IAC and ISC valves 1 or both.
and if stuck idle fails. hot or cold.
no car told why post like that 100 year of cars and 10,000 engines.
????

Should be on or near the fuel injector supply rail.

Low pressure from fuel pump, when the pump is cold the pressure increases, as it warms up the pressure drops (this happens in a pump that is going out) the normal pressure should be at 40 with the key on and engine not running, when started the pressure should stay around 36, any less it won't idle and may run as long as you hold the pedal down. The injectors are opened electronicaly, so as long as there is fuel flow the engine gets fuel to run.So check the fuel pump, soundslike you need a new one

Idle is normally set a bit higher anyway for a cold engine. If the warm idle is OK when the clutch is not engaged and gearbox in neutral, then it points to some kind of severe friction in the area of the clutch throw-out bearing, which may be seizing up, or the clutch pressure plate fingers, one of which may be broken off. If the idle is the same, then that simply needs adjusting.


Is there any odd noise when the clutch is depressed, like a low growl? That will be the bearing. You could have someone listen next to the clutch bell housing while you work the clutch pedal, to try to localise it.

88 ford ranger 2.9 surges buck down when take off in first gear

I would start with cleaning the throttle bore and plate. Then clean the Idle Air Control valve, IAC, as this is the device that controls idle speed. Use a can of spray carb cleaner and an old toothbrush. Trouble with the IAC would make sense if you can keep the engine going by holding down the gas pedal a bit.
Use the carb cleaner to check for vacuum leaks at hose connections and elbows. run engine and spray short bursts at hoses and listen for idle speed changes.
And lastly if problem is still there check MAP sensor.

it may be idle control sensor or a bad mas air flow sensor--maf sensor in otherwords. or could be engine misfire at cold temp. start. only time when cold? or does run better when warm? try warming engine to operating temperature before driving,if problem removes it's self after warm up,up grade gas to 93 octane for 1 tank full. then see if problem goes away. it's cold where you are right? if so the fuel needs to be at least midgrade 89 octane fuel because 87 octane fuel will not start your honda correctly at cold temps. in cold weather 93 or super gas octane will start ,no problem,low octane fuel sometimes gels, or freezes at low temps. if in warm climate, change the fuel filter, add fuel injector cleaner to your fuel tank[preferablly lucas fuel treatment] this will lube your fuel injectors and give better fuel mileage. thank you for choosing fixya.com

it seems that the auto choke setting is maybe wrong or there is a problem with engine management, or a worn part which is sticking.

when cold, the engine should be higher as the choke will be on but a warm up idle of 1200 seem a bit high i would expect around 800 and then on restart if the engine is warm then the choke should be off but the idle being too low indicates one of the above.

Check engine codes.
If it comes up as a Crankshaft sensor... Replace it.
These are the exact symptoms

try changing your egr valve first