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Discussion Starter #1 (Edited)
So as title says. i put a cam in my 4.3l ever since i havent goten it too run right.. it idles fine. all new Delco ignition parts. once i hit 3k rpm the tac goes crazy and i believe its retarding timing maybe the computer thinks its at redline? backfires like crazy until i let off. also when cruising under 3k rpm every couple seconds it kinda stops firing it feels like. just small hickups if that makes sense.. i got a CPS relearn done today at a local shop and it did not change anything...still on stock tune. normally after driving for 20 min it will let me rev it out but the other day it was doing it all the way home (45 min drive) it was also like 1F outside. it drives fine when its HOT no missfires revs too 5k+ no issues atall. very weird problem im having.. Check out the video of it sounds like 2-step going 55mph lmao. Thanks!
Edit- 2001 truck. 2005 4.3l 5 speed manual. 4x4.

 

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time to get cereal
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2,448 Posts
I would guess the stock tune is your problem. It's tuned for the original cam...
 

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Discussion Starter #3 (Edited by Moderator)
I would guess the stock tune is your problem. It's tuned for the original cam...
i think this is more than a tune issue. yes the cam might make the fueling off a bit and not make the power it should. but a cam on stock tune will not make the tachometer go crazy. also people run 270ahr on stock tune and have never heard of this issue.
 

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I finally got blown
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844 Posts
Check your timing. Possibly you have a valve issue maybe do a leak down check b4 tearing the water pump and ft cover off again. If you dont have a leak down tester get a compression tester and fill the cylinders w air and listen for air escaping through the intake or exhaust or valve cover if you have a screwed piston/rings/cylinder wall. Intake or exhaust indicates a valve/seat issue. Valve cover indicates ring/piston/cylinder issue.
 

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94 4x4,01 Blazer
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855 Posts
your cps could be on the way out - hense the randomness above 3k
 
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