comatose at 5500 RPM... please help
04-14-2010, 07:34 PM
#1
comatose at 5500 RPM... please help
So I just wend out driving to try & nail down some specifics about the problem I've been having. The basic gist is that my engine craps a brick or something anytime it sees 5500 RPM.
here's the truck:
'99NBS Sierra 1500 RCSB 4x4
stock 5 speed with an '01 5.3 LM7
AirAid CAI, 3" in / dual 2.25" out chambered muffler
BB 93 tune
this problem happened twice - both times under the same conditions, so i decided to go out on a test drive & bravely try to replicate the problem again so i could get some specifics. here's what happened this time:
I pulled hard in 1st to 5000 with no problem; chirped 2nd & pulled to 5500, and then (with it still in gear) the truck took a literal nose dive as the engine tried to back itself back down. I immediately hit the clutch & the RPMs hovered at 1000. Then whenever I gave it any throttle, the engine speed would go up to 2000 RPM & back down to 1000 continually once a second or so for as long as the gas pedal was depressed. I then turned the engine off & restarted it and kept driving with no problems. As I was approaching a red light, I decided to give it a rev in neutral. A quick rev to 6000 RPM seemed to be alright - it went right back to idle without a hiccup. Then the light turned green, and as I started to pull through the intersection, it got to what sounded like about 2000 (I was making a left turn and didn't expect anything, so I wasn't paying attention) & then tried to fall off again. Once again, I quickly hit the clutch & it sounded like it was gonna do the up-down again when I gave it some gas, so I quickly restarted the truck & continued through the intersection.
I hope this helps find a solution because I ain't got any clue how people can talk about shifting above 6000 all day & I can't get above 5500 without the engine going into a coma. Please help me fix this.
here's the truck:
'99NBS Sierra 1500 RCSB 4x4
stock 5 speed with an '01 5.3 LM7
AirAid CAI, 3" in / dual 2.25" out chambered muffler
BB 93 tune
this problem happened twice - both times under the same conditions, so i decided to go out on a test drive & bravely try to replicate the problem again so i could get some specifics. here's what happened this time:
I pulled hard in 1st to 5000 with no problem; chirped 2nd & pulled to 5500, and then (with it still in gear) the truck took a literal nose dive as the engine tried to back itself back down. I immediately hit the clutch & the RPMs hovered at 1000. Then whenever I gave it any throttle, the engine speed would go up to 2000 RPM & back down to 1000 continually once a second or so for as long as the gas pedal was depressed. I then turned the engine off & restarted it and kept driving with no problems. As I was approaching a red light, I decided to give it a rev in neutral. A quick rev to 6000 RPM seemed to be alright - it went right back to idle without a hiccup. Then the light turned green, and as I started to pull through the intersection, it got to what sounded like about 2000 (I was making a left turn and didn't expect anything, so I wasn't paying attention) & then tried to fall off again. Once again, I quickly hit the clutch & it sounded like it was gonna do the up-down again when I gave it some gas, so I quickly restarted the truck & continued through the intersection.
I hope this helps find a solution because I ain't got any clue how people can talk about shifting above 6000 all day & I can't get above 5500 without the engine going into a coma. Please help me fix this.
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04-14-2010, 08:29 PM
#8
It could be a simple mistrake on Justin's part. It's ok, it's not the first time I've seen those values missed. There's not a lot of manual transmission trucks running around so it just may be simple oversight on Justins part. Doug Rippie Motorsports could never get my truck to go past 5600RPM's after I left it there 2 days. It was doing the same thing your truck is. I got so damn frusterated and mad at DRM that I bought HPT myself and learned to tune myself. That was 5 years ago 
04-14-2010, 09:06 PM
#9
could be... i noticed he also forgot to make sure the 4x4 indicator worked.
thanks for the help.
after looking at my dyno sheet again, i don't think it's quite worth sending it back yet... i could shift around 5000~ish & be alright. that'll put me at 2900 & 3000 on the 1/2 & 2/3 shifts. if i actually end up needing 4th, it'll be right under 3600.
they're gonna have a dyno at the track this weekend, so i'm gonna pull again & see what comes up. sad thing, though, is it's south GA in mid april - it's gonna be in the low 80s with, i'd imagine, normal southern humidity.
i know i'm definitely getting a retune when i finally get my headers & cam. i reckon i can just bring this up then
**edit**
so apparently the 4x4 light issue is due to the 2002 OS just not liking it
thanks for the help.
after looking at my dyno sheet again, i don't think it's quite worth sending it back yet... i could shift around 5000~ish & be alright. that'll put me at 2900 & 3000 on the 1/2 & 2/3 shifts. if i actually end up needing 4th, it'll be right under 3600.
they're gonna have a dyno at the track this weekend, so i'm gonna pull again & see what comes up. sad thing, though, is it's south GA in mid april - it's gonna be in the low 80s with, i'd imagine, normal southern humidity.
i know i'm definitely getting a retune when i finally get my headers & cam. i reckon i can just bring this up then
**edit**
so apparently the 4x4 light issue is due to the 2002 OS just not liking it
Last edited by _zebra; 02-24-2011 at 03:22 PM. Reason: so it wasn't Justin's fault the 4x4 don't work
04-14-2010, 09:13 PM
#10
That part is completely up to you. Why not buy EFI Live from Justin and then do email tunes back and forth? That way he can give you professional advice and at the same time you're not at the mercy of the USPS for sending PCM's back and forth. That way you can make changes instantly and optimize your tune to a "T"