1998 chevrolet silverado 5.7 feels like a engine miss with no engine code

1998 CHEVROLET SILVERADO
7,000 MILES
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JAYDHEAT
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i have a 1998 k1500 with a reman. 5.7 with about 7000 miles on motor. before i replaced the motor had a engine miss with p0300 code. after engine was replaced still had code so put new wire, cap and rotor, miss and code went away. now i have miss back but no code. also replaced intake temp sensor, throttle pos. sensor, map sensor, cat. convertor, engine coolant temp sensor. tried plugs and wires again, went away for 1 day then come back. the intake gasket is new, i think i have rule that typical problem out, (issue doesnt go away when warmed up). please give me any ideas, i love my truck but am starting to get frustrated. btw engine was replaced with 210,000 miles and had developed a knock in the bottom end
Dec 31, 2011 at 7:03 PM
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SATURNTECH9
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Did you reuse your old intake manifold?Did you also reuse you injectors?Also did you ever straight edge the upper and lower intake manifolds to make sure they wernt warped before putting them on?
Dec 31, 2011 at 7:19 PM
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JAYDHEAT
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Yes old intake and spider injection were reused, with new gaskets for lower intake. I have never strait edged intake, but i have tried the starter fluid trick and noticed no change in idle
Dec 31, 2011 at 7:33 PM
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SATURNTECH9
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Using starting fluid to look for a leak i would never do i like to use carb spray.Just because you couldnt find a leak by spraying doesnt mean there isnt a leak and the manifold isnt warped.Its so common for those to warped you must always check them for warpage upper and lower.That has been a issue with those for a while.I would rule that out since you seem to have replaced a lot of the most common reasons for your issues.Also because the problem followed from the old engine.Also how are the spark plugs?Non of them are cracked miss gapped etc?
Dec 31, 2011 at 7:50 PM
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JAYDHEAT
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Plugs are new, gap set not required...bosch platinum 3 i think, may be wrong, cant remember
Dec 31, 2011 at 7:57 PM
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SATURNTECH9
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The most over looked causes for strange missfires are those intake manifolds there junk and warp often.
Dec 31, 2011 at 8:05 PM
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JAYDHEAT
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Shouldnt i be getting some kind of p... Code
Dec 31, 2011 at 8:07 PM
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SATURNTECH9
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If its a slight enough missfire the computer doesnt always set a code for it.So your sure you have a missfire?
Dec 31, 2011 at 8:13 PM
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JAYDHEAT
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Just going by feel, and what it felt like before i changed the plugs rotor cap and wires. I forgot to mention that it happens when im barely on the throttle, say just to maintain cruising speed, or if the cruise is set. If im driving 65 on a flat road in overdrive and just barely have accelerator pressed to maintain speed is when i notice it
Dec 31, 2011 at 8:25 PM
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SATURNTECH9
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So how did it run before you changed the plugs wires cap and rotor driving under those conditions?
Dec 31, 2011 at 8:40 PM
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JAYDHEAT
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Drove the same, but i was getting a p0300. Right after i replaced everything it drove great, didnt miss a beat. The a couple weeks later it was back, with p0300 code, i found that i had a bad rotor (again), replaced with a better rotor and went away. Now its back but this time with no code
Dec 31, 2011 at 8:51 PM
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SATURNTECH9
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Did you check the rotor again?Maybe you have a worn disributor?Thr p0300 code didnt come back after the second rotor replacement did it?
Dec 31, 2011 at 9:21 PM
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JAYDHEAT
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Noand i still have no code, i check it regularly with my own scanner
Dec 31, 2011 at 9:24 PM
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SATURNTECH9
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So no you never checked the rotor and cap again after the problem returned?Also you dont have a worn distribtor?
Dec 31, 2011 at 10:31 PM
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JAYDHEAT
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It very well could be a worn distributor, i am going to start with that and another new rotor, and ill get back with you, thank you for your advice, and have a happy new year
Dec 31, 2011 at 10:41 PM
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SATURNTECH9
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Your welcome keep me posted you have a safe and happy new year as well.
Dec 31, 2011 at 10:46 PM