10-08-2022, 04:30 PM
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#1
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Fuel Smell at Cold Starts
Hey everyone, I tried searching the 3rd Gen section but wasn't finding my problem.
Lately I've been getting a strong fuel smell that comes into the cabin only on cold starts regardless of outside temp. Strong enough to where I need to open a window. Then of course once the temp goes up (about 5+ minutes) the smell is gone.
I did just replace the EVAP Canister with a brand new OEM from Toyota because I had this issue for a few weeks and once I replaced the canister it stopped happening for about a month, but now it's back to smelling and I can't see any visible leaks.
Hoping you kind folks could help prioritize what I need to be looking out for.
Thanks in advance
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10-08-2022, 06:52 PM
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#2
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Until the CAT warms up you will smell it. Colder temps make it worse.
Cold starts cause it it go into fuel enrichment mode. (Old school Choke). It will start out at a cold loop rich as all get out, and when it senses a valid Primary O2 sensor signal it will go closed loop and slowly ramp up the Air Fuel mixture from 8:1 to 14.7:1. By the time the engine hits 180f it should be at 14.7:1 AF and it will update its fuel trim map for the current operating parameters.
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10-08-2022, 09:17 PM
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#3
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Quote:
Originally Posted by 19963.4lsr5
Until the CAT warms up you will smell it. Colder temps make it worse.
Cold starts cause it it go into fuel enrichment mode. (Old school Choke). It will start out at a cold loop rich as all get out, and when it senses a valid Primary O2 sensor signal it will go closed loop and slowly ramp up the Air Fuel mixture from 8:1 to 14.7:1. By the time the engine hits 180f it should be at 14.7:1 AF and it will update its fuel trim map for the current operating parameters.
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So you trying to say this is normal? Because that definitely makes zero sense to me. I had a 97 4Runner for a few years and I never once smelled fuel, then same with this 96. First like year n a half never smelled fuel, and now it happens for a couple weeks, then magically goes away for months.
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10-09-2022, 07:54 AM
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#4
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When was the last time your primary o2 sensor was replaced? I’d start there if it hasn’t been done recently even if there’s no code
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10-09-2022, 11:16 AM
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#5
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Quote:
Originally Posted by McLoven1t562
So you trying to say this is normal? Because that definitely makes zero sense to me. I had a 97 4Runner for a few years and I never once smelled fuel, then same with this 96. First like year n a half never smelled fuel, and now it happens for a couple weeks, then magically goes away for months.
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when the EVAP system has a leak I it will code for a slow leak or rapid leak. In some cases you will smell gas as the tank vents.
Are all your readiness monitors set? EVAP, CAT, and O2?
Valid point about your pre-cat O2 sensor.
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10-12-2022, 06:34 PM
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#6
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I had a fuel smell that i recently resolved by replacing all the hoses coming in and out of the evap system and throttle body. They were seriously dry rotted from the previous owner negligently using E85 and had cracked in unobvious areas. The PO had replaced a fuel line under the intake manifold due to it leaking. If the smell comes back, the next line item will be Injector seals. If you have replaced all the vacuum and evap hoses, you could add a uv dye to the fuel and check around with a light after a few drive cycles. Consider full coverage insurance until resolved, best of luck!
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10-12-2022, 06:35 PM
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#7
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Quote:
Originally Posted by 19963.4lsr5
when the EVAP system has a leak I it will code for a slow leak or rapid leak. In some cases you will smell gas as the tank vents.
Are all your readiness monitors set? EVAP, CAT, and O2?
Valid point about your pre-cat O2 sensor.
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I had LARGE evap leaks with no codes present.
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10-12-2022, 06:58 PM
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#8
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Quote:
Originally Posted by RandyBobandy
When was the last time your primary o2 sensor was replaced? I’d start there if it hasn’t been done recently even if there’s no code
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Only owned it for less then 2 years so definitely that old lol. I went ahead and just bought two new Denso ones that I'll replace this weekend....if anything, can't hurt to swap them out regardless.
I'll likely take another commenters advice too and start swapping out old hoses around the engine bay. I replaced a couple so far just because the previous ones were rock hard, so I'll likely check the condition of more and keep replacing them. Small price to swap hoses and if anything, good preventive maintenance thing to knock out
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10-12-2022, 10:39 PM
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#9
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How is the gas mileage? If the injectors are original, one or more may be leaking when cold.
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10-12-2022, 10:48 PM
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#10
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Quote:
Originally Posted by GRIPGRAIN
They were seriously dry rotted from the previous owner negligently using E85 and had cracked in unobvious areas.
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Some people, you seriously wonder how they ever drive
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10-13-2022, 04:02 AM
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#11
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Fuel Smell at Cold Starts
Quote:
Originally Posted by LittleCaesar
How is the gas mileage? If the injectors are original, one or more may be leaking when cold.
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He should be able to pressurize the fuel system with a jumper wire to look for leaks with the engine off.
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10-13-2022, 01:34 PM
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#12
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i would also suspects leaking injector(s)
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10-13-2022, 05:49 PM
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#13
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Quote:
Originally Posted by LittleCaesar
How is the gas mileage? If the injectors are original, one or more may be leaking when cold.
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Roughly like 14-15 mpg? I get around 200 miles on a tank of gas and takes 13 or 14 gallons at the station. Apparently I have a "low fuel" light but it's super unreliable lol, I'd love to swap the fuel pump assembly at some point but I just don't have the space or tools to do it. In an apartment so I have no jack and no stands, nor a legal spot to drop it :P
Quote:
Originally Posted by 19963.4lsr5
He should be able to pressurize the fuel system with a jumper wire to look for leaks with the engine off.
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really? I'll have to browse youtube to check out how I do that one.
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10-13-2022, 09:13 PM
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#14
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If you’re injectors are leaking through the pintle you won’t see it without a borescope or pulling the injector out of the o-rings and looking for them dripping.
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10-14-2022, 03:50 PM
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#15
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If your injectors are getting clogged there could be some backpressure buildup. RCFuelInjection.com does a good job testing and cleaning them out.
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1999 4Runner(3rd Gen) Base, Engine: 2.7L (3RZ-FE), Trans: 5sp manual (W59)
Miles as of 10-2022: 107k
VIN: JT3GM84R2X0047863
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