Engine seems to always be in load/surging throttle
Jan 20, 2025 | 06:29 AM
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Engine seems to always be in load/surging throttle
Hoping I can get some helpful insight,
I’ve got a 2004 suburban running 35x15.5x20 wheels and a 6.0 bored out to a 6.2 with a 78/85 turbo and about 15k miles on the new motor and turbo and 20ish or so on the whole turbo kit and right now my issue is that it seems that my engine doesn’t want to stay “out of load”. Basically when I’m driving at any speed above 40-50 when I set my cruise and I shift into overdrive my boost guage will read -7 to -6 right after the shift and then basically instantly creep up to 0 psi. It’ll do that at 40 50 60 70 and basically up to 85 and the engine will also stay running rich, prior to this issue when I would be doing 70 I’d be at about -7 to -6 and getting about 14 mpg compared to like 6 mpg, but the rpm’s are the same.
I’ll also when I’m doing below 30-40 if I’m holding a steady throttle the rpm’s will almost like surge at only 2k rpm’s or 3k rpm’s, and occasionally I’ll be at pretty heavy acceleration and if I hold it around 3-35k it is like a 200-300 rpm jumping it’ll do which I’m not sure if it’s because of the road I was on or what. The only thing I’ve really noticed is that my blow off valve is slightly open at idle which from what I’ve read that should be the case (I thought prior to reading that it shouldn’t be) and sometimes when I floor it my boost guage will basically max out at 7.7lbs and will rarely show on my digital guage “overflow” or something for when it goes above 8lbs which is what my wastegate is set at and I can definitely notice that it’s down on power. I also just started noticing a very loud “WHOOSH” from the BOV when I’m let off aggressively which it wasn’t doing before, but would still have this issue. The sound I’m hearing is not a “oh that’s just how the blowoff valve should sound” it’s is significantly different sound then what it’s been for the last year or two.
Fuel pressure is good and have checked and had injectors cleaned. It is a speed density tune and was dyno tuned by a reputable shop and has been running fine for these last 15k-20k miles. Also have not noticed or heard any noticeable air or vacuum leaks, but haven’t had time yet to whip up a vacuum/boost leak tester. Any input is appreciated.
I’ve got a 2004 suburban running 35x15.5x20 wheels and a 6.0 bored out to a 6.2 with a 78/85 turbo and about 15k miles on the new motor and turbo and 20ish or so on the whole turbo kit and right now my issue is that it seems that my engine doesn’t want to stay “out of load”. Basically when I’m driving at any speed above 40-50 when I set my cruise and I shift into overdrive my boost guage will read -7 to -6 right after the shift and then basically instantly creep up to 0 psi. It’ll do that at 40 50 60 70 and basically up to 85 and the engine will also stay running rich, prior to this issue when I would be doing 70 I’d be at about -7 to -6 and getting about 14 mpg compared to like 6 mpg, but the rpm’s are the same.
I’ll also when I’m doing below 30-40 if I’m holding a steady throttle the rpm’s will almost like surge at only 2k rpm’s or 3k rpm’s, and occasionally I’ll be at pretty heavy acceleration and if I hold it around 3-35k it is like a 200-300 rpm jumping it’ll do which I’m not sure if it’s because of the road I was on or what. The only thing I’ve really noticed is that my blow off valve is slightly open at idle which from what I’ve read that should be the case (I thought prior to reading that it shouldn’t be) and sometimes when I floor it my boost guage will basically max out at 7.7lbs and will rarely show on my digital guage “overflow” or something for when it goes above 8lbs which is what my wastegate is set at and I can definitely notice that it’s down on power. I also just started noticing a very loud “WHOOSH” from the BOV when I’m let off aggressively which it wasn’t doing before, but would still have this issue. The sound I’m hearing is not a “oh that’s just how the blowoff valve should sound” it’s is significantly different sound then what it’s been for the last year or two.
Fuel pressure is good and have checked and had injectors cleaned. It is a speed density tune and was dyno tuned by a reputable shop and has been running fine for these last 15k-20k miles. Also have not noticed or heard any noticeable air or vacuum leaks, but haven’t had time yet to whip up a vacuum/boost leak tester. Any input is appreciated.
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