4.0 freaking out
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New User
Joined: Feb 2004
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From: Rose Hill kansas
4.0 freaking out
I have a 91 Ranger xlt 4x4 with a 4.0 in it that is driving me nuts.You can be driving down the road and it will just start to surge hard to the piont that if you shift down to 1st going around a corner on sand it will spine the 35's that I have on back and if you stop and ideal in N it ideals a little fast but will rape up like you taped the pedal.
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New User
Joined: Feb 2004
Posts: 5
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From: Rose Hill kansas
Vin 95 I tested the IAC,TPS and they all are in the specs that my book gives.I thought about the O2 senser's but the specs that are in my book are for a required temp while testing the resistence of the O2 and I have no idea how to decide what the temp is so can't do them, I did find a bad plug wire so I replaced them. Anyone have any ideas on what to try next????? 
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Joined: Feb 2004
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From: Rosebud
Check that you have 12 v going to the 02 sensor,check with key on,engine off.Warn the engine up to normal temp then check the other wire coming back out of the sensor for voltage,it should have be between 0.35 and 0.55(very low).A quick test can be done by getting the engine hot then immediatly disconnecting the sensor connector and probing the sensor wire (sensor side) for millivolts.about .036 or so. When the sensor is hot ,it should produce a small amount of voltage by itself. By the way , are you getting a check engine light? Even if you are'nt you could still have pending codes in the PCM,auto-zone will read them for you for free.
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New User
Joined: Feb 2004
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From: Rose Hill kansas
I cleaned the IAC and checked the O2 and it checked ok. So I just closed every thing up and went for a ride and it is running good! No idea what it was maybe a lose contact and when I pulled it to check and put it back, it made a good contact who knowes but it is running again. 
