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Discussion Starter #1
My truck runs perfectly fine then out of the blue it gets really loud and goes through revs really rough. Still shifts fine and doesn't jerk. But it kind of feels like it loses power when this starts happening. Then it goes away runs fine again and returns randomly. I just had the tranny serviced and there was no shaving's and everything looked clean. Just last week changed the cap/rotor/wires/plugs to see it made any difference and still nothing. Any ideas to what's causing this? It's the 5.7 tbi engine.
 

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Try running some sea-foam thru your vacuum line off your brake booster and see if that helps anything
 

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My truck runs perfectly fine then out of the blue it gets really loud and goes through revs really rough. Still shifts fine and doesn't jerk. But it kind of feels like it loses power when this starts happening. Then it goes away runs fine again and returns randomly. I just had the tranny serviced and there was no shaving's and everything looked clean. Just last week changed the cap/rotor/wires/plugs to see it made any difference and still nothing. Any ideas to what's causing this? It's the 5.7 tbi engine.
Any Check engine lights?
 

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Discussion Starter #4
No, none at all. Last time it had a check engine light it was the EGR and I already replaced that. Never came back.
 

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No, none at all. Last time it had a check engine light it was the EGR and I already replaced that. Never came back.
:-/ ...

Runs fine then randomly gets loud and revs slow..

Couple of questions:
When was the last tune-up done on the truck.
Miles on current plugs / wires / cap / rotor.


Maybe a Cat is backing up / failing? Could remove the y pipe and take a gander in the catylitic converters to see if they are comming apart internally...
 

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Discussion Starter #6
Last time I serviced the transmission was 2 days ago. Thought it would go away then returned. The last time I changed the cap/rotor/plugs/cables was about 8 days ago. So they have maybe like 200 miles on them. Mechanic friend thought it could be the tranny shift solenoids, but I really doubt that because it shifts like a champ even when this happens.
 

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Does your truck have a MAF senser, they can go bad and not throw codes. IAC as well will give all kinds of problems and may not show a code.
 
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