Newbie Needing Help- Idles but surges with throttle blip - SS2 Cam, DBW, Engine Stand

[gcattani]

Morning,
Here's the engine build for reference:
- 2004 GEN 3 5.3L.
- Drive by wire throttle body (DBW).
- Elgin 1840P (SS2) Cam with 0.585/0.585 valve lift. See attached for cam card information. Cam installed straight up.
- Exhaust dumps roughly 18" from manifold, and have some minor baffles within them to muffle noise.
- Only using front O2 sensors, which are installed in the stock location.
- Using Innovate LM-1 Wideband O2 sensor, which is installed 6" from Bank 1 O2. It is not being recorded, only viewed on the Innovate display.
- All engine parts are stock, such as intake, sensors, throttle body, heads, etc.
- Plugs and wires have been replaced.
- Injectors were originally stock #628 and have been replaced with ones flow tested 80lb/hr at 58 lbs.
- Fuel rail system is stock returnless with an inline fuel pressure regulator setup for return to the fuel cell.
- Fuel pump system is an external Walbro 255 with deadhead pressure at the rail set to 58lbs.
- Stock wiring harness was modified for standalone operation.
- The ECU is stock.
- The DBW controller is not original, but one pulled from another vehicle (issue?).
- Stock five wire MAF is installed in order to obtain IAT signal.
- Air intake is a short section of intake tube with MAF mounted

- ECU tune is as follows:
* SD tune with MAF set to fail (using HPT guide to SD tuning)
* Was with stock and 80lb/hr injectors
* Ran the Russ K Idle config, and idle remained relatively

With the engine running on a test stand, the engine's status and issues are as follows:
- Either running the stock and new injectors, starting cold or hot, the engine idles well down to 800-850 RPM.
- Increasing the RPM must be done slowly and gradually or else the engine will jump up in RPM.
- Any minor blip in RPM will cause the engine to surge, hunt for 5-7 seconds, and die.
- While in Idle, I have noticed that the STFT's increase to +30%, so using the Wideband as a reference I use RTT to trim up the fuel in the Idle cells. The fuel trims go quite high and the STFT's do not come down enough.
- I have attempted to trim/add fuel during throttle increases, but the engine's RPM cycles too quickly to adjust properly.

The attached tune is as I left it last night with minor additions from the HPT SD tuning how to.
The scanner log:
- SD-RTT-SS2-80_RussK SD_00
* Slight throttle increase at 2m50s mark
* Throttle blip and dies at 5m45s, 9m25s, 11m55s, 15m38s marks
* Hot start at 6m45s, 10m56s, 13m35s
- SD-RTT-SS2-80_RussK_00
* Ran the Russ K Idle Config

That's about it.
I hope that someone can take a look at the info and guide me in the correct direction. It would be greatly appreciated.

Thanks!

[5FDP]

Too short of exhaust could cause the sensor to act funny, I'd try adding a few extensions to your exhaust to make sure that isn't a problem. I assume your test stand is running 58 psi too right? If you're running in open loop with no fuel trims like the tune says, then you shouldn't be seeing STFT and LTFT in the logs.

Did those injectors come with data? Like min injector pulse, short pulse adder and offset vs volts data?? You need that data if you didn't get it.


Is the drive by wire TAC module and pedal assembly from a similar vehicle? They need to kind of go together to make it happy. They changed them up every few years. Like a 2003-2004 is likely a different part number than a 2006-2007 part type of thing.

[gcattani]

Thank you for the quick reply, 5FDP. Much appreciated.

Regarding the exhaust:
- Stock manifolds.
- The Front O2's are in the stock location, so, a few inches after the manifold collector flange.
- The Wideband is 7" from the Narrow band on bank 1.
- The Wideband is 10" from the exhaust outlet.
- Overall, the complete exhaust from the manifold flange is 20-ish inches.

Fuel System
- Yes, the test stand fuel system is running at 58 PSIG when deadheaded. So, when the pump is running, and the engine is off.
- I have a gauge on the fuel pressure regulator and one on the rail for comparison.
- At Idle, the fuel pressure at both gauges reads 54-56 PSIG.
- The regulator vacuum reference port is connected to the back at the manifold when the engine is running (Idle and otherwise).

Injectors
- No, there is no additional data to the injectors. They are truck-style decapped that have been flow tested, and I was told to leave the stock fuel injector settings as is, and modify the flow rate only.
- The Stock 25 lb/hr injectors have the same surging issue after throttle blip.
- I can always re-install the stock ones for further testing.

TAC Module
- I need to verify the part numbers of the pedal and the TAC module as I don't recall the vehicle.
- The current pedal does activate the throttle body from closed to open, but I notice that with the engine Off the throttle position is not at or near zero. It's around the 15-19% open.

Is there a way to modify the Pedal % to TB position open % ?

Thanks again.