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2013 Chevrolet Suburban
Platform: GMT 400, 800, 900

2004 sub 8.1l volt/idle drop

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Old Oct 18, 2016 | 11:58 PM
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Default 2004 sub 8.1l volt/idle drop

Hi all, new to the forum so I hope I'm posting in the right place.

Here's my issue, when in any gear, under any load at idle my voltage will drop from 14 to 13 and my RPM's from 700 to 500 and sometimes a little lower. No CEL or codes stored or pending.

Things I've tried:

-Cleaned MAF and intake
-Plugs and wires
-Had the auto parts store test the battery and alternator, both tested good

Soon to try:

-Clean all ground points (if anyone knows where they are located that would be great). It's from the the far north so it has some underbody rust issues.
- intake manifold gasket (does this line up with my issues?)
-smoke test for vacuum leaks

Please let me know if you know what the problem is or any direction I haven't already thought of would be greatly appreciated!

Kind Regards,
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Old Oct 20, 2016 | 5:03 PM
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From: kevinkpk
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Does this have a fuel pressure regulator? Sounds like lack of fuel causing low rpms, which in turns lowers the ability of the alternator output
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Old Oct 20, 2016 | 5:18 PM
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Originally Posted by kevinkpk
Does this have a fuel pressure regulator? Sounds like lack of fuel causing low rpms, which in turns lowers the ability of the alternator output
I sure appreciate your feedback, but this year (2004) they went to a returnless system so it's all in the tank now. Any other ideas?
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Old Oct 20, 2016 | 9:10 PM
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Not chasing the issue of the alternator, this is an engine rpm issue in my opinion. Do you have any 400 dtc codes? I'd suspect an egr valve or such i.e.
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Old Oct 20, 2016 | 9:20 PM
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Originally Posted by kevinkpk
Not chasing the issue of the alternator, this is an engine rpm issue in my opinion. Do you have any 400 dtc codes? I'd suspect an egr valve or such i.e.
No codes. Ever! It's just I like a perfectly running vehicle and this really bothers me.

EGR valve is a thought but without a code not sure I'm willing to just spend the money to replace it. I may just clean it and see what happens. Thanks again
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