Hard/weak start when warm?

BRANDONBLEVINS88

MEMBER
1999 TOYOTA 4RUNNER
3.4L
V6
4WD
AUTOMATIC
150,000 MILES

My vehicle starts up perfectly every morning after sitting all night. If I drive into town and run an errand for a short amount of time, when I come back out to start it up, it will start weak or long crank. Sometimes it’ll stumble for a second and then it’s back to running normal. I’ve replaced my idle air control valve, spark plugs, cleaned my MAF sensor, replaced engine temperature sensor and has new fuel injectors as I suspected it was maybe a leaking injector. If the truck sits for a long period of time, it will again start up just fine.

Wednesday, September 27th, 2023 AT 1:57 PM

3 Replies

JACOBANDNICKOLAS

MECHANIC
110,101 POSTS

Hi,

If you have a leaking injector, it would cause a hard start when cold as well. It would allow the fuel pressure to drop off. Also, it would cause raw fuel to enter the engine combustion chamber. As a result, you may see some dark gray smoke from the exhaust, or the exhaust may have a rich fuel-like odor to it.

You have done a lot of work already. Have you checked fuel pressure and pressure drop-off? Has the check engine light come on while the engine is running?

Let me know. Also, take a look at this link and let me know if it helps:

https://www.2carpros.com/articles/engine-cranks-excessively-before-starting

Take care,

Joe

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Wednesday, September 27th, 2023 AT 8:59 PM

BRANDONBLEVINS88

MEMBER
2 POSTS

Unfortunately, I haven’t had a single CEL. The only other thing I’ve noticed is my oil smells like gas. My original suspicion was a bad fuel pump. But no codes. I’ve checked for any pending codes as well and nothing. I haven’t done anything as far as measuring fuel pressure.

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Thursday, September 28th, 2023 AT 4:14 AM

JACOBANDNICKOLAS

MECHANIC
110,101 POSTS

Hi,

If you smell fuel in the oil, you could have a fuel pressure issue. That is where I would start. You have done a lot already, so if you are getting fuel mixing with the oil, suspect the pressure is too high.

Let me know what you find.

Joe

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Thursday, September 28th, 2023 AT 8:06 PM