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TimberJack

Rough idle while cold

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2003 427 has a rough idle until engine reaches normal running temp. It’s like it has a slight skip and while idling the truck shakes. Once you run it up to normal temp is smooths out. I’ve just recently installed new injectors and turbo, witch it had the problem before changing. 

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I’d check specs on fuel pressure, make sure it’s tuned and run it. There are still engines, like John Deere’s 13.5 liter that still run terrible cold.....in 2019. 

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I will put a gauge on it this evening an check it. What should the pressure be? 

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Google “Mack Service Bulletin SB-224-004” for instruction on testing. 

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Could be a crappy eup as well. 

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Is there anyway to test an eup? 

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Bro In my opinion,

  you can chase this for ever! If the truck is pulling well and not throwing codes just ignore the idle situation  ! It could be any number of things !  It may even be the ECM  tring to compensate for a minor compression issue! Just be happy your driving a RELIABLE  somewhat old school truck and not a new one!

Again Just my opinion !

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52 minutes ago, fjh said:

Bro In my opinion,

  you can chase this for ever! If the truck is pulling well and not throwing codes just ignore the idle situation  ! It could be any number of things !  It may even be the ECM  tring to compensate for a minor compression issue! Just be happy your driving a RELIABLE  somewhat old school truck and not a new one!

Again Just my opinion !

I agree. Run it.

As far as testing the eup, sometimes you can lay a couple fingers in the injection line and feel the pulse, some may feel stronger/weaker. If you have one that feels noticeably weaker, that could be your problem, but if you're not sure then I would live with it myself.

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Ten4, thanks for the info. Truck pulls fine believe I will leave it alone lol. 

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