427 LSX Turbo - Compound Problems - U0107
 

So it's been nearly three years since I last drove my truck. Which ended with shooting a rod through the oil pan on my LQ4. Since then, I've been stockpiling parts to get it back on the road. The only "new" variables in this equation are the engine, wiring harness, and fuel system. The truck will start but is extremely rich and will die off. You can manually cycle the fuel pump to keep the truck running for an extended amount of time which leads to indicate too much fuel is going through the injectors. My old setup was tuned with ID1000cc injectors and a Walbro 255. Could the Injector Flow Rate (IFR) have been increased to help compensate for the smaller Walbro 255 to the point that now with a Magnafuel 750 its getting WAYY too much fuel? I'm aware that ID offers downloadable Characterization Tables to input directly into EFI Live. And that will likely be my next step in order to get the fuel issue resolved. From what I understand, most tunes should be built upon the IFR. My next problem is a constant "Reduced Engine Power" throwing code U0107 which is a Loss Communication with TAC (throttle actuator control) module. Could it be doing this because the truck is extremely rich or does that usually indicate a completely separate issue? With the suspicion of multiple issues, I've test the throttle body and X-link which both passed inspections. The only other related items to test would be the TAC module, Peddle Assembly, and Wiring Harness. Would you say I'm getting "Reduced Engine Power" because of the U0107 or getting U0107 because of "Reduced Engine Power"? It's very tempting to yank out factory items and stuff a Holley Dominator in with DBC throttle body but I don't want this to whip me. Also, I've done the obvious things like check all grounds, fresh battery, fuses, etc. Any help or advice would be greatly appreciated!

What's fuel pressure like?

Is it still at 58psi or is the new fuel pump pumping out like 65-70psi and making the injectors push more fuel?

Was the tune updated for the new engine size like with cylinder volume and such so it knows how big it is?

We've tried fuel pressure from 35lbs to 62lbs. The lower fuel pressure seems to help but I know it won't be happy there once we get it running.

The computer currently in truck is tuned on a LQ4/ID1000CC/Walbro255 setup. I took the truck to a tuner and we spent over a day with no success. He couldn't get it to stay out of "Reduced Engine Power" long enough to have any success. Either the truck would be running too rich or it would completely die off, there was no happy medium. But then again, maybe this comes back to injector characterization tables? I'm definitely not a tuner, but have been learning basic principles lately.

The 2 most common Issue causing REP are a wiring issue, or a bad TB. This is why people are converting to cable driven and running a Van Operating system.

How are you checking the TB???

The throttle body fully cycles when the ignition is keyed on but I also swapped to the factory 3 bolt 78mm throttle body (removing X-link) and no difference. This should indicate that the throttle body and X-link are not the culprit. We also performed an ohm test on the X-link and it match the required specifications.

Could the throttle blade still cycle and there truly be a communication error?

UPDATE: We backed fuel pressure down to 18 lbs and the truck will idle without shutting off with an 11.5 AFR. Clearly there has been too much fuel getting pass the injectors but this still doesn't solve the U0107 code and REP.

Sounds like one or more things are connected. What do you mean throttle cycles? I gather it moves when you key on, but does the throttle move with key on engine off while you work the pedal? If so, is the throttle position on the CAN accurate?

Meaning that the blade moves when I press the peddle. It works perfectly fine with key on, engine off. It even seems to work with the engine on.

Not sure if I'm familiar with the term CAN?

What is the throttle position read by a scan tool or the laptop and tuning interface when you're moving the throttle?

Are you scanning commanded and actual TPS? What year is the OS?

For fueling, you really need to get the correct data loaded into the tune for the ID injectors, without doing so you are wasting your time on any other fuel tuning.

Just because It cycles With Key On Engine Off does not mean it's good. Under Boost condition it's putting More force on that blade Vs Naturally aspirated . If the Motor is weak or the internal gears are worn It can error out.

I have seen this 2x in person. :sunot:

Even swaped the parts to an NA truck were it never went into REP. As soon as you apply Boost to it, It goes into REP. Got a Brand New TB an issue went away.

Also The Newest Version of the X link has 2 versions.
1 for Silver Blade TB
1 for Gold Blade TB