I have a 70 chevelle with a LQ4 with ported ls3 heads a cam and ls3 intake. If you give it throttle at all it will start to die unless you tap it and then it will start to go. Any ideas on what could be happening would be greatly appreciated. I just got this thing finished so I guess it could be anything. I got a basic tune for what I had from Race Proven Motorsports but I doubt its the tune since it was fine when i first fired it up. A couple of weeks ago.

 

Still don't have any idea why this is happening. Might I just need a tune?

 

It very well could be. I suggest bringing it down and we will figure it out... I dont see it being anything major.

 

My LS1 swap behaved just like that, idle fine but any throttle and it would die. I discovered I only had about 30psi fuel pressure. Got that fixed and it ran like it should. That would be the first thing I would check.

 

OK, thanks Fran, Need to get it inspected then Ill bring it down.
Weird thing is sometimes if I floor it and it starts to die it might fire back up.

 

Check vacuum line to fuel pump regulator, could be leaking or missing. The FPR must get vacuum from the intake manifold. When you open the throttle you let a lot of air in, but it also needs fuel to go with it and if the fuel comes with a "delayed reaction" it can die.

 

I had same issue only to find I had a fuel leak in a line I had not tightened. Double check your pressure at the rail via the Schrader valve.. I have a gauge on mine for permanent duty, and I only needed 2 fittings and a gauge. The fittings cost me about $13 and the gauge was $30 from summit.

I have 48PSI at idle and when I gas it, it jumps to 56-58 psi.

If you only have a basic tune to just get you going, then you definitely need the tune worked on. Best of luck.

 

Cable or wire throttle body?