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High Rev's at startup? 4.0 OHV


Old 09-30-2007
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High Rev's at startup? 4.0 OHV

Ok I give up, when I start he Xploder it rev's up to 3K rpm's and holds it and slowly lets it back down to Idle. I have done fuel injector treatment, I have cleaned the Throttle body and cleaned the IAC. I can't think of what else might cause this. It is more of an annoyance than anything else. It runs awesome otherwise. Anyone got some new ideas?

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Old 09-30-2007
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I guess 3k is a lil high but....most trucks always start up at a high rev and then calm down.

When your vehicle starts, the ten seconds it runs "closed loop"(i believe its closed as compared to open) which means it is running on preprogrammed startup data. This is because your sensors don't immediatelly start working so it just runs in a safe manner.

Other than that explanation which didn't offer any real helpful advice, I blame corn.
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Old 09-30-2007
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I have this problem to with my 2002 ranger except it doesn't go up to 3k it sit's at about 1,500 which normally would make me think its fine but it only does it every once in awhile like this morning when i first started my truck up it did it then tonight when i got off work it didn't do it. so i dont know
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Old 09-30-2007
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open loop is when cold cause the loop is not complete (think of an on/off symbol I 0 )
and you may have a vacuume leak and once the computer goes into closed loope it figures it out and ajusted the idle..

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Old 10-01-2007
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My 06 FX4 revs to about 2000rpms then settles down pretty quick.

3000 is too high. I'd look for a vacuum leak first.

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