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Thread: 4.8 swap, runs rich and is virtually undriveable. O2 sensors? Bad tune?

  1. #1
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    4.8 swap, runs rich and is virtually undriveable. O2 sensors? Bad tune?

    Hey guys, I'm new to the forum and hpt in general, but I was hoping someone could take a look at this run file and see if theres something I'm missing. I swapped a Gen 3 4.8 into my '58 Ford. I plan on running a single turbo down the line, but for now I'm running everything bone stock just to work out the kinks that I expect to run into off the bat. Needless to say, things got pretty kinky. I didn't expect to smoke tires off a stock tune, but I'd just like to get this sucker driving reliably so I can give my wife her car back haha.

    When I say stock I mean completely stock, with the exception of fresh lifters and vette valve springs. I reworked the harness (I'm an electrician) and made it standalone, welded up some motor mounts, a trans mount and some exhaust. I flipped stock truck manifolds and welded v clamps onto them, made a crossover and currently have the exhaust dumping out where I plan to land my turbo (passenger side, front corner of engine bay) with an o2 sensor bungs placed right after the manifolds on both sides.

    I am using a 2002 6.0 Escalade PCM (0411) with a Blue/Red connector harness. Starting off, I deleted the VATS, removed ECT from GM800 (DBC throttle body), set up my fan, and removed emissions and rear o2s from the DTC tab. Engine fired up, but it was clear that it was running stupid rich. The vehicle is almost completely undriveable at this point, despite being able to rev while in park and all that. I could get it to go around the block, but the RPM would drop real low whenever I would let off the gas/come to a stop, even completely stalling out a few times. Actual driving is pretty choppy, definitely like its bogging out or whatnot. Okay, so what did I expect? I'm running a 6.0 tune on a 4.8. I hit up the tune repository and downloaded a stock 4.8 tune, cleaned up all of the stuff that I had already done (VATS, etc) and then segment swapped the Engine and Engine Diagnostics tabs from the Factory 4.8 tune onto my current tune. Now we're cooking. Right? Wrong. Don't get me wrong, its "better" but its still not anything I could laughably take on the road. Still runs rich, still bogs, still stalls out when I stop, etc. But I was able to dog leg myself to the nearest gas station for a fill up and a slurpee, so I at least feel good about that.

    So rather than waste more of your time, I'm just going to post a log file and see what you guys think. Like I said, I'm new to HPtuners, but I'm dying to learn. My main goal isn't balls to the wall power at this point, I'm just trying to get my ride back on the road reliably and safely so I can flex on all of my coworkers who said I'd never get this swap done. I definitely don't want to break or melt anything while I'm at it, so any help or advice is super appreciated. I've also included the tune file as well in case anyone wants to take a crack at it from that end. Thanks in advance dudes!

    A few things to point out:
    -O2 sensors. I'm using black tipped 4 Pin Square Bosch ones, part number 13474 to be exact. These are listed as downstream sensors, I'm only running upstream sensors. Also, apparently the black square plugs meant they were case ground. I have the tan wire that goes to Blue Pin 63 (o2 sensor low reference ground) so does that mean I would need isolated ground sensors (white square 4 pin plug) or am I just chasing my tail on this? Reason I bring this up is because my O2 Voltages in the VCM scanner only seem to read 0-4, maybe 0-9mV regardless of engine speed, load, etc. while mostly fluttering around 0mV. If there's any weight to that reading, it would mean that I'm reading super lean, right? not exactly the case since I can visually tell (and smell) that I'm running pretty rich.
    -Fuel Trim. LTFT is looking at about 25% throughout the entire run file, while STFT is looking pretty much all over the place. Not too sure what this means, so I guess peep that file and tell me how much of a noob I am.

    wtfisgoingon.hplex58segswap.hpt

  2. #2
    Tuning Addict 5FDP's Avatar
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    If the exhaust is dumped and you are still running o2 sensors, that may cause an issue. You need at least 18-20in of exhaust past the sensor so it can't skew the readings.

    Without cats in these engines, it's pretty much always going to smell rich as well. If your fuel trims are going nuts and adding in fuel to fix an issue it thinks is there, that will make it even worse.

    Get the correct upstream o2 sensors is what I'd do. Don't bother will the sensors you have if they are indeed downstream sensor part numbers. That is a for sure issue and will cause the horrible running problem if the computer tried to go into closed loop fueling. I bet it would run 5x better if you used the scanner to disabled fuel trims and closed loop. It would run on just the stock calibrations for fueling and not take any corrections from the o2 sensors.

    That is also assuming you are running the proper 58psi of fuel pressure that is required.

    You need to disable cat over temp as well, with no cats or rear o2 sensor you want that disabled.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
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    Ordered some different sensors (13193) and that made all the difference. Thanks for confirming my suspicions on that. I suppose I should have just paid attention to the color of the plugs on my harness; male white 4 wire square plugs, which would indicate isolated ground. I don't know how I missed COT, but that has been disabled as well. Thanks for catching that.

    All in all, the truck drives much better. I still have a few things to tighten up so I haven't been able to take it to freeway speeds yet, but I'm going to work on getting some logs of that soon. This scanner is pretty sick. I don't even have a functioning speedometer on this truck, so I'm feeling pretty spoiled. There is a slight bog if I catch it out of gear, but I'm assuming these are small quirks that the PCM will correct as I drive?

  4. #4
    Tuner in Training
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    do you have your MAF running/connected in tune file? I am in the middle of a street tune and disabling the MAF makes a big difference on tuning and I will probably leave it disconnected in hp tuner if you have a iat in Maf you cant unplug it just disable maf in editor/hp tuner if you have a big cam good luck on idle tuning its been a nightmare