LS3 lost power at high elevation

[blznnp]

Hello all, I just picked up a 68 camaro with a LS3 installed in it a couple weeks ago. When driving from Bend, Or to Seattle, Wa I went over a mountain pass that topped out at 5700 ft I believe. The car was running great up till around 5500 ft, at that point it started acting like it had no fuel in it. It had only used about 5 gallons so I know it had gas but it sure seemed like it was out. It would idle fine and rev find when in neutral but once I put it in gear and started to drive it would go a little ways then start cutting out on power. when it first started I was in 6th gear, I down shifted and it started running better for a few seconds then started acting up again. Got it back down to Salem, Or which is a good amount lower and it ran fine. I have been running it for two weeks in Seattle, so at sea level, and it has been running fine. One GM tech told me I need a Baro sensor, but I was under the impression that the MAP should take care of everything and I shouldn't have any problems with a fuel injection system. Anyone heard of this or have any ideas to help me out?

[rickpaw]

Starving for fuel? Did it have a full tank of gas?

What's your fuel tank set up?

A friend in our club had similar issue while driving in Co mountains. Granted he has a throttle body EFI set up. He had a stock fuel tank with an out side pump. The stock tank does not have internal baffles so during cornering and under half tank, the fuel pick up will get uncovered and starve the engine of fuel. Switched to a tank designed for EFI/in tank pump, and solved his issue.

[blznnp]

It has a aftermarket EFI tank with baffles. It still had around 13 gallons if gas in it.

[EFI69Cam]

I drive ls powered vehicles between 5300 and 6500 feet every day here in Denver. I do not experience any problems as you described. What engine control system are you using? Does it have a OEM calibration?

[68birdls1]

Do you run a MAF or speed density? I've heard. If the car had a speed density tune and it's tuned at a low altitude that it will greatly affect how the car drives at a higher altitude.

[andrewb70]

I've drive my GTO over the continental divide, through Rocky Mountain National Park. I think it gets over 11K feet. I have the GMPP harness and ECU kit and it ran well. It was down on power as you might expect at high altitude, but there were no issues like you described.

What ECU are you running? With an OEM set-up that uses both a MAF and MAP, there should be zero issues at altitude.


Andrew

[blznnp]

I am running the stock ecu that came with the engine from GMPP, Stock tune and all. Getting it tuned tomorrow, and going to see what the tuner says about the current tune. I agree with you guys that I shouldn't have this problem. Only 1000 miles on the setup when this happened.

[andrewb70]

I am running the stock ecu that came with the engine from GMPP, Stock tune and all. Getting it tuned tomorrow, and going to see what the tuner says about the current tune. I agree with you guys that I shouldn't have this problem. Only 1000 miles on the setup when this happened.

I seriously doubt that it is the tune.

What does your fuel system look like? What are you using for a regulator? details...details...

Also, how is your MAF sensor installed? Did you follow the instructions that it needs to be in a 4" tube and must have a certain length of straight pipe in front of the sensor to work properly?

Andrew

[blznnp]

I bought the car how it sits. I assume it has the right size intake pipe and the location is correct. I will measure it tonight. The only thing I know about the fuel system is that it's all new, EFI tank, walbro lph400 fuel pump.

[blznnp]

Got the car dyno tuned yesterday, running awesome. Now time to hook up my scanner and take it to the mountains and see if I can get it to duplicate what it did before