Fast start when engine is warm

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SC_4RunnerSC

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Before I go any further I have searched for answers on the forum. Some threads were close to my symptoms, but not exact. New battery, alternator, starters, battery cables

So when my engine is cold, it starts normal. Whenever I am running errands or traveling and the engine is at operating temp-it will start extremely faster than a normal cold start. Any thoughts? The mechanic I take it to is stumped and can’t figure it out. He said maybe an electrical issue
 
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The fuel pump will not tun o until it gets a signal from the crank position sensor so that's mostly a 1.5 to 2 second after engaging the starter at cold.

When hot the fuel pressure is probably already there and it starts faster taking less time to fire up.

Most vehicles turn the fuel pump on when the key is in the on position. The 3rd gen 4 runner waits for the signal before enabling as a safety feature.



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If you just replaced the battery it may need to relearn it’s hot idle IAC position. It’s an adaptive parameter that goes to factory default when the ECU looses power.

Could be a dirty IAC also. What does the hot idle settle to after a hot restart?


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brillo_76 said:
The fuel pump will not tun o until it gets a signal from the crank position sensor so that's mostly a 1.5 to 2 second after engaging the starter at cold.

When hot the fuel pressure is probably already there and it starts faster taking less time to fire up.

Most vehicles turn the fuel pump on when the key is in the on position. The 3rd gen 4 runner waits for the signal before enabling as a safety feature.



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So I should look into the crank position sensor? Thanks for the info, I’ll do some research
 
19963.4lsr5 said:
If you just replaced the battery it may need to relearn it’s hot idle IAC position. It’s an adaptive parameter that goes to factory default when the ECU looses power.

Could be a dirty IAC also. What does the hot idle settle to after a hot restart?


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This happened before I changed the battery as well. It’s been happening since I bought it 2 years ago. It’ll start every time no matter what, just super fast when warm. And when it’s warm, it’ll settle around 700rpm or so? I don’t drive it daily or actually much at all. Have a company car that I use every day
 
This is normal for these 3rd gens. What you are stating is normal behavior. :-)

Idle settling around 600 700 rpm is normal when all warmed up too.. :-)
 
I don't see the problem. It's normal for the engine to start easier when warmed up.

My 4runner will start almost immediately when I twist the key and the engine is warm. Takes longer when it's cold, but no more than a second even then. The RPM will be above 1000 at idle on a cold start and go down to 700 rpm. Everything your describing is normal engine behavior.

Do modern cars not behave this way anymore? Every car I've been in with a twist key has always started easier on a warm engine.
 
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Interesting…my 2005 4Runner and wife’s 2019 Highlander does not have the same starting when engine is warm. Both start the same as a cold engine.

But anyways, thank you everyone for letting me know it’s just the way these engines are. It’s a big relief for me, but I will however clean the IAC when I get a chance. Thanks everyone!
 
SC_4RunnerSC said:
By faster I mean this. When engine is cold, it’ll take say 2 seconds to start or so. Whe engine is warm and operating temp it’ll start in like 1/4 of a second
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My truck does this, too and always has. I don't believe it's an issue or a problem however.

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I am kinda surprised a newer 4 runner doesn't do it. As it's very common in Toyotas to do this. Not sure about the cars etc. But the trucks and 4 runners all still should. I check and see if my 09 tocuma does it...:)

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brillo_76 said:
I am kinda surprised a newer 4 runner doesn't do it. As it's very common in Toyotas to do this. Not sure about the cars etc. But the trucks and 4 runners all still should. I check and see if my 09 tocuma does it...:)

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Click to expand...


In American cars each manufacturer takes a different approach. Like Toyota not starting the fuel pump until key is in the start position.

One approach is how many degrees of crank rotation (pickup pulses) they decide to use before arming the fuel and ignition systems.


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