Backfire through injection upon quick throttle off of idle

[Nobleone]

Ok guys, I am new to this forum and tuning. I have signed up for the tuning course but I need to try and get my car somewhat tuned for Power Tour in 2 weeks. I have been working on it and it is running pretty good. I have been referencing the training material supplied by The Tuning School to get the car running well. The car is a 68 Nova with a 355 LT4 from a 96 Corvette. I have installed a Torqhead conversion to eliminate the Opti spark and run the LS1 coils and computer. Torqhead sent me a base tune and I have adjusted timing and perimeters to get the car to idle well and throttle up very well. I haven't taken it out on the road yet as I have this backfire upon giving it a quick hit on the throttle. If its over 1200 RPM's, it doesn't do it and revs smoothly and quickly. It only does it when it is idling at 850 RPM's. Anyone have any ideas or can steer me in the right direction. The car ran well before I did the conversion with the OBD1 computer. I did the conversion as I have another motor on the stand I will be putting in but figured I could use this engine as my trial and error before doing any harm to the new engine. Any help is greatly appreciated.

[kingtal0n]

it sounds like it might not be getting a good signal at low rpms. Trigger signal could be weak. Just a random suggestion, if the "conversion" hardware (just a guess) has an amplitude adjustment maybe turn it up. Another thing is shielding, perhaps the trigger wire is UNSHIELDED or TOO CLOSE to the ignition signal. Just random ideas.

[Cheapjeepoffroad]

Ok guys, I am new to this forum and tuning. I have signed up for the tuning course but I need to try and get my car somewhat tuned for Power Tour in 2 weeks. I have been working on it and it is running pretty good. I have been referencing the training material supplied by The Tuning School to get the car running well. The car is a 68 Nova with a 355 LT4 from a 96 Corvette. I have installed a Torqhead conversion to eliminate the Opti spark and run the LS1 coils and computer. Torqhead sent me a base tune and I have adjusted timing and perimeters to get the car to idle well and throttle up very well. I haven't taken it out on the road yet as I have this backfire upon giving it a quick hit on the throttle. If its over 1200 RPM's, it doesn't do it and revs smoothly and quickly. It only does it when it is idling at 850 RPM's. Anyone have any ideas or can steer me in the right direction. The car ran well before I did the conversion with the OBD1 computer. I did the conversion as I have another motor on the stand I will be putting in but figured I could use this engine as my trial and error before doing any harm to the new engine. Any help is greatly appreciated.

Did you ever solve this? I'm having the same issue on a LQ4 LS

[edcmat-l1]

Did you ever solve this? I'm having the same issue on a LQ4 LS

The most common reason for a backfire in the intake is a lean condition. In carburetor speak, it needs more pump shot. In an EFI application like the GM OE controller platform, there is no real acceleration enrichment. The most common fix is dialing in the VE by forcing speed density. Once the VE is all dialed in, if it still does it, increasing the VE table in the 80 Kpa and up region, from your 400 rpm column up to about 1600 usually cures it. Also need to make sure it's not dropping all the timing out of it at the same time. You'll need to know where you end up in the timing table with a quick stab of the throttle. Most timing tables drop the timing out as your load increases at low RPM.