408 LQ4 problems
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Teching In
Joined: Oct 2008
Posts: 5
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From: WA
408 LQ4 problems Hi guys, my dad built a mild 408 for his 99 Silverado 1500 (use to have a 5.3 in it). Anyway I will explain the problems were having and at the bottom I will list the mods on the engine and specs. I am not so sure this is a tuning issue, right now Vince at Trifecta is working with us and e-mailing us tunes to try to make things right but I think it might be something else, hard to say.
When you start the truck up a lot of times it will sit there and idle fine around 800rpms, then when you put it in reverse or drive it immediately dies, then there are other times it will be fine and go right into drive or reverse, it seems to do it worse after the truck is warmed up all the way. Also when you stab the throttle it hesitates for a second then it wants to take off. So far no pinging that we can hear at all so we know the timing is probably retarded quite a bit (running on 87 octane). Let me know what you guys think, here are the mods.
Eagle 408 Stroker with stock LQ4 aluminum heads (mild porting)
10:1 compression ratio
224/220 Comp Cam
Fast 102 Intake Manifold (ported)
Fast 102 Throttle Body
Precision 42lb injectors
Fast Billet Fuel Rails
Fuel pressure set at 61psi
AEM Intake with stock MAF (Will we need to upgrade the MAF?)
Stock fuel pump (for now, have a walbro 255 waiting to go in)
13 inches of vacuum at idle
I believe that is it, if I can remember anything else I will add on to the list, thanks for the help in advance and thanks again to Vince for working his tail off trying to help us get this thing right.
When you start the truck up a lot of times it will sit there and idle fine around 800rpms, then when you put it in reverse or drive it immediately dies, then there are other times it will be fine and go right into drive or reverse, it seems to do it worse after the truck is warmed up all the way. Also when you stab the throttle it hesitates for a second then it wants to take off. So far no pinging that we can hear at all so we know the timing is probably retarded quite a bit (running on 87 octane). Let me know what you guys think, here are the mods.
Eagle 408 Stroker with stock LQ4 aluminum heads (mild porting)
10:1 compression ratio
224/220 Comp Cam
Fast 102 Intake Manifold (ported)
Fast 102 Throttle Body
Precision 42lb injectors
Fast Billet Fuel Rails
Fuel pressure set at 61psi
AEM Intake with stock MAF (Will we need to upgrade the MAF?)
Stock fuel pump (for now, have a walbro 255 waiting to go in)
13 inches of vacuum at idle
I believe that is it, if I can remember anything else I will add on to the list, thanks for the help in advance and thanks again to Vince for working his tail off trying to help us get this thing right.
