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Discussion Starter #1
Hello All, I have a 97 f350 auto 4x4, the idle fluctuates from around 500 to 700 rpm. When I come up to a light or put it in gear from a stop or the ac is on it goes from 700 or so rpm down to around 500 rpm and stays down around there, or comes up slightly. The truck seems not to be compensating for being under minimal load in gear, ac on etc... My buddy has the same truck and his stays at 700 rpm regardless. So what is going on with mine????


Thanks
 

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Have you replaced the cam sensor lately ?
 
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Discussion Starter #3
It was replaced this year from the dealer, or so they said they did.
 

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How many miles? Mine got a lot better after injector o-rings...
 
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Discussion Starter #5
I have a little over 140K.
 
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Discussion Starter #6
Anything else to consider???????
 

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Check the icp sensor, front drivers head by hpop, if you unplug it and the engine smooths out, your sensor is bad, goes into limp mode and throws engine light. Did this on my truck, replaced icp and now nice smooth idle and faster startups. Get the part from the dealer, better quality
 
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Discussion Starter #8
I have replaced the ICP as well as rebuilt the fuel bowl and new IPR. Still same problem. It will do it in park or while pushing on the brake coming to a stop, When in park I hold the rpm up to 1k then take my foot off the pedal then it falls down to 500 or less and stumbles. It will come up to the normal idle mark of around 700 after a few seconds. New fuel pump, fuel pressure is where it should be. I am at a loss, any other suggestions?????
 

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the cam sensors are not that reliable, i have gone through half a dozen, the gray ones from the dealer does fail, i just replaced one that was only a month old from the dealer, the speed sensor(abs sensor) may cause the symptoms also, could be a ground problem,you may just have to start ruling out things, hows it shift? i think you can rule out a fuel issue, i would check and clean your grounds first then test and replace the abs sensor and get a new cam sensor since they are affordable now, speed and cam sensor should cost 75 or 80 for both.
 
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Discussion Starter #10
It shifts good once in a while.Most of the time it shifts into gears too early, alot of the time it does a double shift, kinda hard to explain but basically not a firm shift into a gear more like a sloppy roll into a gear. Definately not a consistant steady firm shift into the gears. I have replaced the cam sensor twice.
 

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I would try the abs sensor in the rear diff, easy to install and only costs $30, and a reflash of the computer, does your overdrive light ever flash while this is happening? the abs sensor goes out and will cause all kinds of issues with shifting and driveability, good chance thats the problem, also check the diff fluid when you pull out the old sensor, i think it can get a bad signal if the fluid is low or very dirty, good luck and let us know what happens.
 

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It definitely can screw up the signal...I had constant PO500 codes and changed the sensor twice along with the harness..I was going to run wires directly to the PCM..Then I changed the rear end oil which was quite dirty and there was a chunk stuck to the magnet ..the codes stopped appearing
 
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Discussion Starter #13
BUMP

Still having the same problem with low stumble idle. When in park it will also do it. If I hold the rpm at 1K while in park or neutral for a few seconds then let off the pedal it will stumble down to 450 - 500 ( as it appears on needle) for a second or two then return to normal. I have friends that have the same trucks 3 ea and their trucks do not do this. I have a federal truck with no fuel pulse dampener maybe that has something to do with it?? I do not know anyone else who has a federal truck to compare to. Maybe it is an injector related problem. I have no cel or od light does not flash. Anyone have any idea???
 
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Discussion Starter #14
BUMP it up
 
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