Help me out, LS3 Swap Project tips

[99socalfrc]

Finally got my 68 Camaro LS3 fired tonight. I'm hoping someone can give me a few tips on how to start with a tune that will at least get this thing to the exhaust shop. The combo is a Crate LS3 with a 229/236 cam and long tubes. Trans is a 4L70 but I'm not overly worried about that. I'm mainly asking for help with the initial steps to take on this E38 ECM to get the car up and running as far as idle quality. Right now it just has open headers on it and I need to get it to the exhaust shop to install wideband bung, mufflers etc.

Couple of things I noticed in the few minutes the car idled in the garage:

1. The O2 sensor on bank 1 started out reading about 475mv and went down to reading only 18mv in the course of 2-3 minutes. What could this mean?
2. Both 02 sensors seem to be reading unreliability due to the open headers, sensors are about 2 inches from free air
3. The car had really bad bucking in drive, not so bad in reverse but it will barely stay running in drive with any throttle to it. This is what concerns me.

Any help on what to do is appreciated.

[5FDP]

Is this vehicle running no MAF sensor?

Looks like the MAF is half way failed in the tune but needs to a few more settings to make it fully failed and run in speed density. If you aren't going to using a MAF set the MAF fail high and low to 2hz and 1hz. Then set your 3 MAF dtc's to fail on first error (P0101 - P0103).

Then you would want to disabled closed loop so it doesn't use the o2 sensors because the sensors being 2in from the open air in the exhaust is screwing them up. You can set the LTFT to have the MIN ECT match the max at 284 so it's not using LTFT to correct fueling, then the ECT vs Startup ECT is the main controller for closed loop, set that to 284 so it runs in open loop the whole time. Hopefully that should get it to run okay and let you drive it a short way. Or just trailer it.

[99socalfrc]

Is this vehicle running no MAF sensor?

Looks like the MAF is half way failed in the tune but needs to a few more settings to make it fully failed and run in speed density. If you aren't going to using a MAF set the MAF fail high and low to 2hz and 1hz. Then set your 3 MAF dtc's to fail on first error (P0101 - P0103).

Then you would want to disabled closed loop so it doesn't use the o2 sensors because the sensors being 2in from the open air in the exhaust is screwing them up. You can set the LTFT to have the MIN ECT match the max at 284 so it's not using LTFT to correct fueling, then the ECT vs Startup ECT is the main controller for closed loop, set that to 284 so it runs in open loop the whole time. Hopefully that should get it to run okay and let you drive it a short way. Or just trailer it.

Thanks so much for the input.

The car is indeed running an LS3 MAF, so I guess I start there. The ECM I have was used previously in a swap that was SD, but I intend on using the MAF. I thought I had everything changed back over to run the MAF, could you please let me know what I missed on that.

I'll setup the LTFT fail as you mention tonight and give it a shot, from the readings on the O2 sensor going to 18mv I just know that reading isn't helping me out.

Thanks again for the input, it is appreciated.

[5FDP]

Alright so it is running a MAF, then just set the MAF fail high and fail low HZ settings back to that of the LS3 MAF sensors you are using. You may have to find what those settings are from another tune. Then make sure the MAF curve is the same for the LS3 MAF to start with. You will have to make adjustments to the curve once you really start tuning it.

[99socalfrc]

Alright so it is running a MAF, then just set the MAF fail high and fail low HZ settings back to that of the LS3 MAF sensors you are using. You may have to find what those settings are from another tune. Then make sure the MAF curve is the same for the LS3 MAF to start with. You will have to make adjustments to the curve once you really start tuning it.

I have an 08 Corvette tune I'm using for reference, I had the curve copied but missed the MAF fail stuff. In fact I missed all the Airflow stuff under diagnostics. Thank you so much I'll load the updates tonight and see about pissing off the neighbors some more with the noise.

[99socalfrc]

5-6 attempts to move it out of the garage have failed. it won;t start very easy, and once I get it started it runs for 8-10 seconds, surging begins and it dies.

Can anyone help me on what I can do to at least get this thing to move?

[99socalfrc]

I'm getting P0068 and PO106 codes

[5FDP]

Post a log too.


Those codes are MAP related and can cause problems with the car running.


I noticed another things just quickly going over the tune, the VE tables don't match. One is some what smooth and the other is just a choppy zig zag and both aren't complete either as they drop off after 100kpa. I think the resolution has gone down because of the 2 bar os upgrade. That and the o2 sensors being in open air pretty much with the tune still having closed loop enable.

[99socalfrc]

I can't get much of a log as it won't stay running long enough.

Regarding VE I just want it to have the stock 08 Corvette values. I used that in all the coeffecient tables, so what have I done wrong to have a VE table other than stock? I did notice the VE tables stopped at 100 kpa, but I'm new to the E38 stuff so I figured I just didn;t know what I was looking at.

How can you tell it is 2bar? Tat is not my intention. I was under the impression I had a stock OS ECM here.

[99socalfrc]

I reset the codes and used the Electronic throttle settings from a 08 Trailblazer SS. It idled for a bit longer and died the instant I put it in reverse.

[5FDP]

Edit > calibration details > controllers. It says it's a 2 bar OS.

So somehow you changed it from a regular 1 bar setup to a 2 BAR OS.

If you still have the stock tune, just reflash the vehicle with that. Then you can redo any tables you you already had done, like the VVE, MAF curve, MAF settings etc etc.

[99socalfrc]

All I have is the 2008 Corvette tune from the repository. The ECM cam with some of the junk you noticed (like the VE table.

Can I change back to a 1bar OS that easy?

I basically wanted to put a stock 08 Corvette tune in this ecm and use it. I did not know this was a 2bar ecm.

The corvette tune does not have the VVE tables, just the coeffecient ones. What do I do to correct the VVE tables?

[99socalfrc]

Should I just load the 08 Corvette tune into the ECM. I have been manually copy and pasting the tables but perhaps just writing the enitre ECM is the way to go? Then I could read entire and change me tables? Would this get me back to stock like 1 bar tuning?

[99socalfrc]

Looks like the 2 bar OS is what I am stuck with unless I get a different ECM? Damn this sucks.

Moral of the story, never buy used parts.

[5FDP]

The VVE tables on that corvette computer would be under the EDIT tab too, most GEN 4 computers would have the VVE under the edit tab. Make sure it's in advanced view under the EDIT tab too.

Because the OS has been upgraded the VVE under the edit tab on this silverado computer is gone, and now it just has regular VE tables for normal IMRC open and closed.


You can still run this car with a 2 bar tune, I was just pointing out that it is different and the VE resolution has changed. I'm not sure what will happen if you tried to write a corvette tune on this computer, it could work or it might brick the computer and you are out 2 more credits (because you have to license the corvette tune) and a PCM.

There is no way to revert back to stock with HPT unless you had the stock file for it as far as I know. Maybe others will have idea's on what you could do. Other options are to buy a computer from a dealership that is for a corvette and tune that. This way everything will be like a corvette to start with, then fueling, MAF/VVE/timing and all that jazz would be to be tuned because of the camshaft upgrade and headers.

[99socalfrc]

The VVE tables on that corvette computer would be under the EDIT tab too, most GEN 4 computers would have the VVE under the edit tab. Make sure it's in advanced view under the EDIT tab too.

Because the OS has been upgraded the VVE under the edit tab on this silverado computer is gone, and now it just has regular VE tables for normal IMRC open and closed.


You can still run this car with a 2 bar tune, I was just pointing out that it is different and the VE resolution has changed. I'm not sure what will happen if you tried to write a corvette tune on this computer, it could work or it might brick the computer and you are out 2 more credits (because you have to license the corvette tune) and a PCM.

There is no way to revert back to stock with HPT unless you had the stock file for it as far as I know. Maybe others will have idea's on what you could do. Other options are to buy a computer from a dealership that is for a corvette and tune that. This way everything will be like a corvette to start with, then fueling, MAF/VVE/timing and all that jazz would be to be tuned because of the camshaft upgrade and headers.

Do I need a different MAP sensor other than the stock LS3 one to run this ECM?

[99socalfrc]

OK just so I understand the 2bar upgrade does not in any way mean I cannot use this ECM. It means my VE tuning will be done thru the IMRC Open/Close tables instead of the way a typical 1bar E38 would. Beyond that I get access to lower temp fan settings and some of my tables are scaled different than a typical E38.

I need to make the 2 VE tables copies of each other and not use the shitty looking one. I'm going to try and get the VE table looking better and see what I can do about avoiding those MAP codes and try again tomorrow.

[99socalfrc]

Made it off the ramps and out of the garage!!!

It died in the driveway basically at the very hint of throttle, but it's better than yesteday.

I have attached the current tune and log. I think it may be way overfueled in the VE tables but have no way to verify because I have the LTFT disabled and for some reason my STFT do not show up in the scanner???

[99socalfrc]

I took a shot in the dark that the tune was too rich and after some adjustments to the VE and MAF it runs! I made three trips yesterday just around the block and such.

Today though, on my way to the exhaust shop I had problems. I got code PO606, the big problem here is the ECM basically shut down the electronic throttle. So the car will now only idle around it won't accept any input from the pedal.

My question is, I'm running an E38 from a 08 Silverado, will that work with an LS3 TB? I suspect a couple of the problems I've had are coming from the computer going into limp mode because of numbers from the TB and pedal not jiving. I've tried adjusting the Electronic throttle settings but I've noticed the scaling on the E38 I have is different than the LS3 tunes I'm studying.

Does anyone have input on whether or not a new LS3 crate motor throttle body can be made to work with the 2008 Silverado ECM? Would I need to source an LS2 TB?