ZR-1 Net Registry Forums - View Single Post

8upZR1 · 11-15-2006

Its been a while, but I have excellent news, my LT5 fired and runs. In the end it was the lifters. I installed a new set and they seem to do the trick. I have never heard of compression varying like mine did but it is absolutely possible.

Now it seems that I have an even bigger problem. The motor will fire but it takes forever to crank and ussually you have to floor the throttle for it to fire. The mixture is crazy rich so I am guessing that the ecu goes into flood clearing mode when the throttle is floored. When it runs it will nit idle by itself, you have to give it gas. Performance is awful. It feels like a small displacement big turbo car in 5 th gear at 20 mph. It literally cannot keep up with traffic. But once the motor passes about 4K RPM it starts to run normal. But getting to 4K is a serious struggle. Full race engines have snappier low end torque. I refuse to believe I lost this much low end torque from porting the intake. Its just impossible. So what could it be? Fuel pressure looks great, the O2 sensors are new and they look like they are behaving normally, except that they show rich for the first 4K rpm. My secondary throttles are removed, but they always have been. No SES light or codes to be found. I was thinking maybe Idle air control but then why would everything be OK up top. I have tried 2 computers, one with haibeck chip, and the other with a GM piece. No difference. Engine key doesn't make a difference either. Why so much fuel? I just dunno. This Lt5 has been a mission to say the least.

But at least I can cruise aroubd town in my vette. I thank everybody who gave me input and helped my figure out this machine.

11-15-2006	#17
8upZR1 Join Date: Jun 2006 Location: Thunderbolt, Ga. Posts: 253	Re: LT5 technical problem Its been a while, but I have excellent news, my LT5 fired and runs. In the end it was the lifters. I installed a new set and they seem to do the trick. I have never heard of compression varying like mine did but it is absolutely possible. Now it seems that I have an even bigger problem. The motor will fire but it takes forever to crank and ussually you have to floor the throttle for it to fire. The mixture is crazy rich so I am guessing that the ecu goes into flood clearing mode when the throttle is floored. When it runs it will nit idle by itself, you have to give it gas. Performance is awful. It feels like a small displacement big turbo car in 5 th gear at 20 mph. It literally cannot keep up with traffic. But once the motor passes about 4K RPM it starts to run normal. But getting to 4K is a serious struggle. Full race engines have snappier low end torque. I refuse to believe I lost this much low end torque from porting the intake. Its just impossible. So what could it be? Fuel pressure looks great, the O2 sensors are new and they look like they are behaving normally, except that they show rich for the first 4K rpm. My secondary throttles are removed, but they always have been. No SES light or codes to be found. I was thinking maybe Idle air control but then why would everything be OK up top. I have tried 2 computers, one with haibeck chip, and the other with a GM piece. No difference. Engine key doesn't make a difference either. Why so much fuel? I just dunno. This Lt5 has been a mission to say the least. But at least I can cruise aroubd town in my vette. I thank everybody who gave me input and helped my figure out this machine.