Extended crank time when warm

[jmanous]

Hey all,

My 07 MT 72K miles 1nz-fe has trouble starting when it is warm for a week or so.
Usually when warm, it will crank for long, then even misfires (RPM ~250) and then
slowly come back alive to its normal 600 RPM idle. When this happens,
the crank speed is great, so I have ruled out battery and wiring issues
(which I have cleaned among with the ground to the body).

I have tried to leave the car in ON for the pump to get some time to build up
pressure but I am not sure it helps.

The car starts instantly when its cold.

So searching I came up with this list:
- faulty fuel pressure regulator
- faulty fuel pump
- leaky injector
- clogged fuel filter

- bad spark plugs
- bad ignition coils
- crank position sensor

I have noticed something weird today, oil is 2.5K miles old but smells like gasoline.

Also, I cannot hear the fuel pump buzzing when its at ON position.
On the other side, there is no hesitation whatsoever in the car. Normal torque, no misfires ever, no erratic behavior. How can a fuel pump gone bad when there is
absolutely no sign of power loss?

Any input would be greatly appreciated.

[ilikerice]

You can probably rule out spark plugs, coils and cps. If those are bad, those dont get better when its cold. You will also have a check engine light on and possibly a flashing check engine light if a coil is bad.

if you smell gas in your oil, which I don't think you really are, but to be sure, go ahead and change your oil to make sure that it isn't murky.

yaris fuel pump is very quiet. Doubt you will hear it turn on and if it isn't on, your car will not be running at all.

Fuel filter is possible, maybe some bad gas at your last fill up. The strainer (filter) is connected to the fuel pump inside the tank.

If there is an actual misfire, you should have a check engine light coming on. Will be either random misfire or a cylinder.

Check your vacuum lines and charcoal canister.

[B.B._07]

Sounds like a bad coolant temp sensor. If the sensor thinks the coolant is cold it will cause the engine to run rich which is required for a cold start, and this could also explain why you smell gas and why it runs poorly when it does start.

https://www.youtube.com/watch?v=umjDiWKHxjs

[jmanous]

Thanks ilikerice, B.B._07, will check filter and canister but I expect their effects to be more profound
when I was accelerating... I agree that none of these makes it better when its cold. Vacuum
lines can be an issue as I run an aftermarket CAI which kinda stretches the hose, although I
checked today and no sign of wear.

In any case I am waiting for a code scanner to see for any errors.

Coolant temperature sensor.. that makes sense. Does anybody has the voltage range of
the sensor? If it is stuck at minimum temperature, it should be able to tell.
* EDIT: Searching I found other folks measuring the resistance (not the voltage at operating conditions).

[jmanous]

So I got the ODBII reader today. No faults found.

The coolant temperature sensor is fine, got working temperatures of 80C.

Problem is still there, will pump some new gas and see if it persists.