surging motor
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New User
Joined: Jul 2004
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surging motor
This is my first post and I am looking for some help with my truck motor. I just put an rv cam into my 88 f 150 302 efi. It runs great and the bottom end pull is fantastic. But every once in a while the motor starts to surge. the revs would drop to about 4-500 and then surge to about 1500 and then drop again. It doesn't happen all the time and I am trying to determine if it is when the motor is hot or not but there doesnt seem to be any specific time that this surge will start. Any one have any ideas on what is happening or how I can cure this would be greatly appreciated.
Junior User
Joined: Nov 2004
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kaelor, this problem originated only after you installed the new cam? You say rv cam. Does this mean a ford cam that was the number listed for the same engine in an rv application or an aftermarket hi-po cam that supposedly has "rv" performance charachteristics? Either way, is it by chance some super high lift, high durration cam that is causing the lope? Could you have bought a mild cam that was either ground wrong or boxed wrong and is really the cam for a top fueler? 
If the cam is not the issue i would suspect you have an issue with the iac/isc. A vaccum leak could be causing the iac/isc to be not responsive because it is out of range. I hate to ask, but did someone adjust the non adjustable throttle plate stop screw that is ofter mistaken for an idle adjustment? This would cause the identical problem to what you described.
Hope it gives you a starting point and some questions to think though. Good luck.
If the cam is not the issue i would suspect you have an issue with the iac/isc. A vaccum leak could be causing the iac/isc to be not responsive because it is out of range. I hate to ask, but did someone adjust the non adjustable throttle plate stop screw that is ofter mistaken for an idle adjustment? This would cause the identical problem to what you described.
Hope it gives you a starting point and some questions to think though. Good luck.
Freshman User
Joined: Feb 2003
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goo...the screw that's behind that plate that's connected to the throttle linkage isn't the idle adjustment screw???...oops.
i believe i'm missing a vaccum line from my iac i dont' know where it starts tho so i can't find it. Could someone lead me to the other end of the vacuum line that's supposed to be there.
i believe i'm missing a vaccum line from my iac i dont' know where it starts tho so i can't find it. Could someone lead me to the other end of the vacuum line that's supposed to be there.
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