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  #13  
Old 10-19-2010, 11:44 AM
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Re: 4.7 HO Engine Rough Idle Problem

Of course that didn't work, seemed to at first until I went and drove it, then it was right back to doing it next time i stopped at a stop sign, idled down to about 350-400 rpms.
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  #14  
Old 10-19-2010, 03:27 PM
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Re: 4.7 HO Engine Rough Idle Problem

Just took it to a guy I know he was thinking it might be a mass air flow sensor, the shop is going to look at it more in depth tomorrow and see if they can solve the problem, I'll let everyone know what it is when they find it.
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Old 10-20-2010, 11:09 PM
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Re: 4.7 HO Engine Rough Idle Problem

Got an update from my mechanic today. He pulled the valve covers off and discovered that one of the valve lifters on #6 cylinder had failed. That apparently caused that cylinder to have no compression, hence the very rough idle condition (engine was only running on 7 cylinders). Will keep you all updated on what happens next.
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  #16  
Old 10-21-2010, 10:20 AM
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Re: 4.7 HO Engine Rough Idle Problem

Strange that you didn't get any fault code set, misfire for example, for the #6 cylinder. When one of the valves doesn't open, there will be no combustion and the PCM should have noticed this and set a DTC. Or was the failure one of the hydraulic valve lash adjusters?
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  #17  
Old 10-21-2010, 10:58 PM
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Re: 4.7 HO Engine Rough Idle Problem

Might've been the lash adjusters now that you mention it. I'll know for sure once they complete the repair.

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Originally Posted by Frango100 View Post
Strange that you didn't get any fault code set, misfire for example, for the #6 cylinder. When one of the valves doesn't open, there will be no combustion and the PCM should have noticed this and set a DTC. Or was the failure one of the hydraulic valve lash adjusters?
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  #18  
Old 10-22-2010, 05:32 AM
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I just told someone else to pull the valve cover to check for loss of compression by making sure a cam follower didn't pop out, lifter not fail, ETC...
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  #19  
Old 10-26-2010, 10:36 PM
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Re: 4.7 HO Engine Rough Idle Problem

An update - turns out that in addition to the bad lifter, the intake valve in #6 cylinder wasn't seating properly. They had to pull the head off again and replace the valve. Seems to be running fine now. Just glad I've got it back before winter sets in.
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Old 03-08-2012, 06:51 PM
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Re: 4.7 HO Engine Rough Idle Problem

were the valves burnt or damaged in any way,that would explain the loss of compression issue you were having,which cylinder or cylinders had low compression?more than likely static timing of the timing chains is your rough idle,if it ran well before the heads were off i suspect the cam timing is off
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Old 03-15-2012, 08:28 PM
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Re: 4.7 HO Engine Rough Idle Problem

I did have the same problem and when check the codes I got P0325 #1 knock sensor. I read a lot about the TPS & IAC been just plain dirty together with the throtle body, so I bought carburetor cleaner remove the resonator I got an Overland 2004 with the 4.7 V8 HO to show the TB the TPS & IAC cleaned all very throughly, replaced air filter and bingo idles like new!!Just need now new plugs they are on the way, since I just bought my toy with 79000 miles on the clock!!
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