slight shake at idle, comes and goes?
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Elder User
Joined: Mar 2009
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From: eastern shore,MD
slight shake at idle, comes and goes?
i had started to notice that at idle my truck shakes a little, kind of like a miss, but the motor does not change , and the RPMs do not change. the truck runs and drives fine. just that little stumble at idle. it does not do it all the time. I have changed the fuel filter, run 3 tanks of DK gray bottle. with no help. where should i start looking?
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Joined: Aug 2009
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From: Missouri
i had started to notice that at idle my truck shakes a little, kind of like a miss, but the motor does not change , and the RPMs do not change. the truck runs and drives fine. just that little stumble at idle. it does not do it all the time. I have changed the fuel filter, run 3 tanks of DK gray bottle. with no help. where should i start looking?
Posting Guru
Joined: Sep 2006
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From: Montana
Check the connections to your valve covers. The external ones are easy to see, but the most common disconnect is under the valve cover. The connection goes through the gasket with a connector on either side. The UVCH (Under valve cover harness) likes to wiggle free. It will throw a code, but it can cause a rough idle (and eventually rough runing) as the connection gets looser. When you check it, check for a burnt pin as well.
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Joined: Dec 2012
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From: Oakdale, CA
Very likely. Sounds like a common "Ford gray CPS" issue.
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Postmaster
Joined: Apr 2012
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From: North Georgia
In the data grid... once the motor is at full operating temp... check off all 8 rotational velocity boxes... put it in drive... and just hold your foot on the break...
0.0-0.5 is what you want... higher numbers on any one cylinder CAN be related to injector problems... but say in TXtinct's case... the perdel readings were crazy bad on #3... changed out injector... absolutely zero change in readings... reason being... no compression on #3...
Just an example... but yes it can be a wonderful troubleshooting aid...
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I have the same issue the original poster is describing.
OP, try unplugging your ICP sensor, bet the shake at idle goes away.
Don't bother replacing your ICP sensor, because it will still happen with a new sensor (at least in my case).
I have tried the grey CPS, dark blue CPS, an the Borg Warner original black spec'd CPS. No change at all.
Truck is currently at a mechanic for diagnosis. Will let you know what they find.
OP, try unplugging your ICP sensor, bet the shake at idle goes away.
Don't bother replacing your ICP sensor, because it will still happen with a new sensor (at least in my case).
I have tried the grey CPS, dark blue CPS, an the Borg Warner original black spec'd CPS. No change at all.
Truck is currently at a mechanic for diagnosis. Will let you know what they find.
Hotshot
Joined: Jan 2011
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From: Puget Sound
I've chased this before. When the truck is cold, the ICP is higher and the SOI is earlier. As the oil warms up, every little nuance in the truck can have an effect on how smooth the idle is... right down to the brand of oil you use. When was your last oil change?
New User
Joined: Apr 2013
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I'm having the same problem and it's driving me nuts. Didn't notice a vibration until I changed the HPOP to T500. First day blew out ICP, pulled plug to ICP idle smoothed right out. After changing ICP only lasted one day. Vibration is back. could it be a problem with to much oit pressure. No gauge nor do I have a scan tool. Don't know why the ICP goes so fast. Can't keep changing that $$$$$.
Hotshot
Joined: May 2005
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From: Stevens Point, WI
What about the IPR?
Mine does it as well with gray CPS. I have changed all the injector o-rings as well as fuel bowl rebuild, IPR o-rings, 50 cent mod, the whole deal. I haven't tried unplugging the ICP. I believe like Tug mentions, unplugging the ICP raises the pressure some which will make a weak injector act "right" again.
Mine does it as well with gray CPS. I have changed all the injector o-rings as well as fuel bowl rebuild, IPR o-rings, 50 cent mod, the whole deal. I haven't tried unplugging the ICP. I believe like Tug mentions, unplugging the ICP raises the pressure some which will make a weak injector act "right" again.
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Elder User
Joined: Mar 2009
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From: eastern shore,MD
well here is some more info, it is not giving me any codes. the oil was changed 2 months ago. rotella 15-40w. fuel psi is 65psi. i have a scan gauge, is there anything else you think i should check?
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Unless I missed it, which CPS are you running?
