2008 Tahoe LTZ 5.3L
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Sorry to say I think it'* a vacuum leak between the intake and the heads somewhere.
I don't know how you have confirmed that there are absolutely no vacuum leaks and I'm not attacking this, however, these engines will do exactly what you are describing when there is a vacuum leak on an intake port gasket.
I bet if you take it for a drive in this condition it responds fairly normally at speed, then has the issue at idle.
I don't know how you have confirmed that there are absolutely no vacuum leaks and I'm not attacking this, however, these engines will do exactly what you are describing when there is a vacuum leak on an intake port gasket.
I bet if you take it for a drive in this condition it responds fairly normally at speed, then has the issue at idle.
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With long term fuel trims at -11 and -13.looks as if the computer is trying to lean the fuel out. did you try unplugging the MAF while running and see what the fuel trims do. Have seen many skewed MAF sensors do this. Does this vehicle show alcohol Content? If it does, look at the pid for it. Some times you get a skewed reading showing high alcohol content will make the car want to go lean when it has regular fuel at 10% or less. If it does just reset it. I don't remember off hand if that year had it or not.
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It only seems to act like this when there’* a load on the motor example AC, PS, all 4 window motors at same time and only In IDLE parked everything seems to be fine while driving or even in gear but not moving.
TOday I had the throttle body relearn done again and had the fuel trims reset, maf cleaned again. I guess I’ll see how it’* acting shortly. Still seemed to hunt a little bit. And LFT were -20% at one point
TOday I had the throttle body relearn done again and had the fuel trims reset, maf cleaned again. I guess I’ll see how it’* acting shortly. Still seemed to hunt a little bit. And LFT were -20% at one point
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I’m going to put in a new delco alternator tomorrow. This one is starting to make noises. As far as eliminating vacuum leaks I’ve sprayed a can of starter fluid around the ports where the manifold and gasket meet. I understand this method can not always be 100% I’ll have it hooked up to a smoke machine tomorrow.
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Well had it hooked up again today issues seemed to go away after the second relearn and resetting fuel trims. Wasn’t able to recreating the surging under any loads. Alternator output was dipping low with loads and wouldn’t rise with rpms so just replaced with a new 160amp delco. Everything seems fine but will keep an eye. Thanks for all the ideas.
