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Discussion Starter #1
So when I go to slow down, my tachometer goes nuts, even when I let off the brakes and coast the engines rpm jumps up and down, from around 1k down to 400rpm and back and forth till I completely stop, what is the cause fellas? I can't find any bad vaccum lines or leaks anywhere?

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Discussion Starter #3
How is your mpg? Looks like it is almost bogging out. Could be drag on the serpentine by a bad idler pulley maybe?
I had an ultra gauge on it for a few months, till I fixed all the codes on it, and best I got from it was 23.4mpg, it runs and isles smooth all the time,except under slow braking, if I brake hard it will only jump 1 time, idk wth is up
 

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Just a thought have you battery checked. These trucks get all kinds of fucky when the battery starts to go. Probably not your issue but worth a try. You may also try removing the belt and spin the pulleys to check for drag. Have you cleaned maf, map sensors. May also be worth a can of throttle body cleaner to look for vac leaks (spray down vac lines and see if idle changes) again probably not your issue but easy to do none the less and it could help. How old are your spark plugs?
 

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You sure no vacuum leaks related to the brake booster? Are your vacuum lines still pliable or are they old and brittle?
Nice and pliable

Just a thought have you battery checked. These trucks get all kinds of fucky when the battery starts to go. Probably not your issue but worth a try. You may also try removing the belt and spin the pulleys to check for drag. Have you cleaned maf, map sensors. May also be worth a can of throttle body cleaner to look for vac leaks (spray down vac lines and see if idle changes) again probably not your issue but easy to do none the less and it could help. How old are your spark plugs?
I haven't checked the battery or any sensors, the plugs are about a year old.

When you cleaned the throttle body did you pull it and clean it or clean it bolted to the intake mani. That's exactly what mine was doing and while the throttle body didn't look bad it was really bad on the back side.
I pulled it, did a thorough cleaning


I'll check puppies, and test the battery next, alternator too, sometimes my dome light flickers, it may be a charging issue
 
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