strange high rpm miss
01-08-2015, 07:11 AM
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Staging Lane
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Join Date: Jan 2006
Location: Lexington, KY
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strange high rpm miss Been a while since I've been here.
I have a 5.3 T56 conversion in a 92 full size. The truck has had the engine transmission in its current state for a few years and has been 100% trouble free.
Recently if I pull hard up to 5000 or so rpm then shift the truck feels like it hits a wall and has what seems to be a miss for a second or so then pulls out of it. When it revs back to 4500-5000 rpm then shift to third same thing.
If I free rev the truck to 4000 or so then catch it at 2500-3000 rpm and hold the throttle there it will miss for a couple seconds then clean out.
No weird sounds. It idles fine, pulls hard off idle all the way through the rpm range , just seems to hit a wall at the gear change.
I can lug the motor down pretty hard with no misfire.
No codes.
I scanned with hp tuner and didn't see anything that jumped out, but with my inexperience with evaluating the information it would have had to slap me for me to see it.
some truck/engine specs are below
any help would be greatly appreciated.
thanks
Patrick
'92 Fullsize, swb rc
5.3L/T56 conversion, comp XR275 HR cam .566/.568 lift 222/224 duration 112 lsa, crane dual springs, trick flow push rods, K&N Filter, Nelson Performance tune, Keisler shifter relocation kit, Boyd Coddington Smoothie II 18x8 235/55 up front, 18x10 295/45 out back, 2/4 drop, eaton lsd w/4.56 gears
I have a 5.3 T56 conversion in a 92 full size. The truck has had the engine transmission in its current state for a few years and has been 100% trouble free.
Recently if I pull hard up to 5000 or so rpm then shift the truck feels like it hits a wall and has what seems to be a miss for a second or so then pulls out of it. When it revs back to 4500-5000 rpm then shift to third same thing.
If I free rev the truck to 4000 or so then catch it at 2500-3000 rpm and hold the throttle there it will miss for a couple seconds then clean out.
No weird sounds. It idles fine, pulls hard off idle all the way through the rpm range , just seems to hit a wall at the gear change.
I can lug the motor down pretty hard with no misfire.
No codes.
I scanned with hp tuner and didn't see anything that jumped out, but with my inexperience with evaluating the information it would have had to slap me for me to see it.
some truck/engine specs are below
any help would be greatly appreciated.
thanks
Patrick
'92 Fullsize, swb rc
5.3L/T56 conversion, comp XR275 HR cam .566/.568 lift 222/224 duration 112 lsa, crane dual springs, trick flow push rods, K&N Filter, Nelson Performance tune, Keisler shifter relocation kit, Boyd Coddington Smoothie II 18x8 235/55 up front, 18x10 295/45 out back, 2/4 drop, eaton lsd w/4.56 gears
