Slow start up 3.4
08-22-2012, 09:48 AM
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Slow start up 3.4
Guys, my 4runner seems to take a while to fire up, battery is good and starter turns over fast enough, just seems like it takes several seconds for it to fire.It runs perfect when its started... Rode in coworkers 4runner yesterday with a little more miles on it than mine and his does the same thing....Is this common with these or what could i look for? I have a check engine light thats the rear O2 sensor would this be throwing off the mixture of fuel air at startup ? My 3.4 tacoma never had any problems like this it fired right up .
08-22-2012, 04:42 PM
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I have noticed that mine doesn't cold start very quickly either. I also noticed that I can't hear the fuel pump prime when I turn the key to ON like I can with my '94. That makes suspect that the fuel pump check valve may be getting weak and letting the pressure bleed off after a long shutdown, meaning it takes more time for the pressure to come back up during cranking. That's my educated guess, anyway. Tomorrow I'll have had my Taco for all of three weeks and I'm still learning about it at a rapid pace. 
And no, the rear O2 sensor doesn't affect fuel mixture. It's only there to verify that the cat converter is working. What's ironic is that a lot of those sensors fail before the factory cat does.
And no, the rear O2 sensor doesn't affect fuel mixture. It's only there to verify that the cat converter is working. What's ironic is that a lot of those sensors fail before the factory cat does.
Last edited by Dirt Driver; 08-22-2012 at 04:43 PM.
08-22-2012, 04:46 PM
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Or, the fuel pressure regulator is getting weak letting the pressure bleed down. Does it take longer on the first start of the day and less time for the others? All about the same?
08-23-2012, 10:02 AM
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Honestly, its about the same all day, seems like a little worse after a short trip though.
08-23-2012, 03:33 PM
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It's the fuel pump. Very common problem in these. The reason you don't here it prime is because it does NOT. The pump only gets power during craning cycle and after it's started.
Toss in a new fuel pump man.
Toss in a new fuel pump man.
08-23-2012, 07:46 PM
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04-08-2016, 09:12 AM
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Reviving an old thread here, but my 2010 Tacoma (new to me as of this past Dec) is doing this. Mine is much more likely on first morning start, or after truck has been sitting. Suspect fuel pressure regulator in this case versus the pump?
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