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93 4runner rough idle/vapor locking

Old 03-21-2016, 08:24 AM
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93 4runner rough idle/vapor locking

I've got a 93 4runner that is running rough and vapor locks if left off for more than ten minutes or so. I've done quite a bit of searching and can't find a definetive answer anywhere. It just had the head gaskets replaced as well as new valves. Any help would be greatly appreciated.
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Old 03-21-2016, 08:56 AM
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Not likely to be vapor lock on an engine that has relatively high pressure fuel injection.

Check the fuel pressure under different conditions.

I'd guess you more likely have a flooding issue than a weak fueling problem.

Maybe the cold start injector, or regular fuel injector is leaking down after shutdown.
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Old 03-21-2016, 10:38 AM
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Normally I would agree, except in order to get it to start after sitting for a few is to crack loose the fuel line at the rail and nothing but vapor comes out, and then it will start right up. But still runs like crap no matter what.
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Old 03-21-2016, 11:21 AM
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The Fuel Pressure Control system http://web.archive.org/web/201503060...ne/99fuelp.pdf is there to deal with vapor lock. You might as well check that.

Don't forget that EVERY time you "crack loose" a fuel line you must replace the two crush washers. They are one-time-use. Not a place to tolerate a leak.
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Old 03-22-2016, 02:40 AM
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Checked that, nothing obvious wrong, which vsv is it though? Seeing that there are several under the hood. The only sensor that hasn't been replaced is the maf.
However driving home yesterday it kept shutting off as I came to a stop.
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Old 03-22-2016, 06:34 AM
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Originally Posted by deltazlt View Post
...
However driving home yesterday it kept shutting off as I came to a stop.
That doesn't sound like vapor lock. Have you checked basic igntion timing? Are the plugs still firing right up to when it dies?
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Old 03-22-2016, 07:53 AM
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It only vapor locks after being shut off for a period of time, and yes when it would cut off it start right back up and be fine until I push clutch in again to stop.
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Old 03-22-2016, 05:17 PM
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I installed a intake on the truck this evening in doing so had to mess with maf, and when it was all said and done the truck is idling fine now so I'm suspecting a bad maf as at least part of my issue. From what I research about the vapor lock is that no one has truly found a solution to the issue
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