Tim.S
Member Since: 30 Mar 2024
Location: Bristol
Posts: 10
  
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| V8 Petrol engine possible vacuum issue. |
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Any thoughts greatly appreciated!
Ive developed what feels like but isnt a misfire at idle. Starts a few seconds after starting then becomes less obvious as the engine gets up to temperature. Otherwise runs and sounds ok, no engine lights no lack of power.
First thought was the pressure control valve which ive changed and after breaking the old one apart there didnt seem to be anything wrong with that either. All pipes look good and it pulls a good vacuum when felt at the inlet or oil cap.
If I bypass the whole vacuum system by pulling the PCV off and blocking it then it idles fine but if I block off the inlet its still lumpy.
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 9th May 2024 9:28 pm |
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Tim.S
Member Since: 30 Mar 2024
Location: Bristol
Posts: 10
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If anyone is interested it turned out to be the EGR valve where it bolts to the aluminium elbow after the throttle valve. Seems that a previous owner had stripped the thread from both bolts then just glued them back in.
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| 27th May 2024 9:40 am |
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Captain Crosscheck
Member Since: 03 Sep 2021
Location: Oslo
Posts: 324
 
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Glad you got it sorted! Did you have any error codes? And oh! how I hate stumbling upon previous owner/mechanics cock-ups 
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| 27th May 2024 9:13 pm |
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Tim.S
Member Since: 30 Mar 2024
Location: Bristol
Posts: 10
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No lights on the dash and annoyingly these things seem to run quite happily on 7 cylinders! so trying the process of unplugging the coil packs one at a time was only partly useful.
I used a Bosch diagnostic system which whilst not the best for this engine it did have a misfire counter so I was able to see that cylinder 5 was considerably worse than the others and took a chance on it being the coil pack.
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| 27th May 2024 9:24 pm |
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