Long post but basically an EVAP question. Just giving all the preliminary information first.

I freshened up an LQ4/4L80E in a 2003 1500HD with 799 PRC ported heads, TX Speed Stage 2 truck cam, TX speed long tube headers, 3 inch dual exhaust through high flow Magnaflow cats and Magnaflow xflow muffler, LS7 lifters, CHE trunnions, push rods, Melling oil pump, cam sensor, oil pressure sensor, knock sensors and harness, NGK plugs and 8mm ceramic plug wires, CircleD 2200-2400RPM torque converter and then had it tuned. Now the problems - After doing this the truck is having a hard start on the first try occasionally and is running lean. I'm pretty sure I could hear some pinging. It also still didn't have power under load, such as pulling a hill or trying to pass someone. (so, lots of money and still a turd wagon). Throwing p0327 knock sensor code and an O2 code. First thoughts was fuel delivery issue. Checked the pressure with key on engine off and it was a little low at 48-50 psi. I replaced the pressure regulator (Delphi), filter (Wix) and the fuel pump (Delphi). These changes bumped pressure to 55psi. Issues still existed. The next thought was exhaust leaks because the exhaust shop i had finish the exhaust did the absolute worst job i have ever witnessed. Leaking so bad the condensation was dripping through welds. Cut all that out last weekend and built a stainless exhaust system and replaced the MAF sensor. Fired right up and seemed to run a little better. after a few hundred miles the CEL was right back on. When i replaced the fuel pump I noticed that the original fuel tank pressure sensor was there but no wires connected to it. the new pump comes with a new pressure sensor so i just assumed the previous owners must have just unplugged the og pressure sensor when it failed and i would just plug the new one up. but i cant find the wires for it anywhere. i guess they cut them off or pulled them back somewhere. I'm assuming the EVAP system will not work at all without the sensor but would this cause a fuel delivery issue??

 

I'm no evaporative emissions expert but I would start asking your tuner some questions...You are running premium fuel of course?

 

89 to 93 octane only. It's remote tuning, i have HPtuners. i will send him logs for adjustments but just wanted to make sure its not any mechanical problem or some weird evap issue first.

 

An LQ4 with 799's with stock chambers should be about 10:1 and EASILY handle anything from 87 octane on up. Gen IV 5.3's are about that and run on regular 87 octane as a matter of course. Sounds like fueling issues.

 

^^^ yup. If its pinging on 87 you have tuning issues.

 

Ok, thanks. I'll send logs and get a retune. But after investigating the EVAP I have found the tank pressure sensor and the canister vent solenoid to not have any wires on them. The wires are no where to be found on the truck. Does anyone know if thats just because its an HD truck and not a 1500? did they have different systems? What commands the purge valve to open if there is no data from the pressure sensor and there is no way to close the vent valve?

 

EVAP stuff doesn't matter. i completely bypassed the canister and vent solenoid. i vented the tank to atmosphere and capped off the purge valve. Still a hard start and lean.

 

The Evap System is not causing your issue.
The issue is with the tune it self. Mail order tunes can sometimes be hard to nail down. Hopefully they have all the details on the engine combo.

You Need to log what's going on under the conditions where you have the most problems. If its pinging and pulling timing, they should be able to adjust the fueling/timing in those area's of the table.

You may need to work with a local tuner in your area so you can go on a drive and show them the issue's you are having first hand.

 

Post your tune.

 

and data log

 

Start logging before you start the engine. Do this hot and cold.

 

Here are my logs and tune. I've been busy in the shop and haven't gotten a chance to get back on here. i have some new FIC 42lb injectors coming.

 

Log of startup. Failed to start on first attempt as you can see in the log. Erratic spark and something seems off on the 02 sensors, B2S1 mV drops way down while B1S1 stays flatlined around 625mV. Then B2S1 starts switching before B1S1. The STFT data is showing to be very rich under load, correct? Any time I am commanding power it has KR.