Help with LS3 Engine Problems
Thread Starter
Staging Lane
Joined: Sep 2006
Posts: 64
Likes: 2
I'm slow getting back, life is in the way.
I drove the car briefly, maybe a 1/2 mile. No miss at idle and no miss at part throttle. The engine still emits a fine black smoke and a smell that could choke you. While the power seems good, the performance is off compared the 2006 GTO I used to own. This is with new injectors and a new FPR. I can't drive any more until I resolve brake issues. Brakes are worse and car is very unsafe, will barely stop, soft pedal and full travel of pedal.
The 10 PSI drop in half an hour is with new injectors and FPR.
I think it may be a tune issue at this point. As far as electrical, I have 2 gauge wire grounding the engine and to the frame of the car, connected to shinny sanded metal. No separate grounds to the heads. I have separate 8 gauge wiring (+12 and ground) powering the PCM. There is a 6 gauge wire from battery to alternator. There is almost no measurable voltage drop across any of the wires. However adding a wire to the heads would be easy, the PCM is grounded about 18" from back of one of the heads.
I haven't talked to them about the engine tune, just the transmission, I wanted to make sure my tune/hardware would support the GM Supermatic 4L70E. Because of the length of time that has passed from purchase, they can't even look up what they sold me.
I have a stock GM crate LS3 engine 430HP, the MAF in the tune was to support a 2006 GTO MAF and not the LS3 type. I am an electrical engineer and write process control software, but I don't know much about HP tuners or the parameters needed to make the engine run well. The learning curve is very steep and of course a screw up could destroy the engine. To me the biggest thing that stands out is the MAF table. I would have though it should be the same as a Trailblazer. The trailblazer and GTO use the same MAF sensor. The MAF table doesn't look like it was taken from any stock table that I could find in the HPT listing of tunes. The tune I posted is the original Speartech program, the only changes I have made was to correct parameters for tach and gear/tires.
I will have to take a look at the MAP values when I can get a chance.
Problems with flooding at work and no heat at my house is getting in the way right now. When I can get to it, brake work is probably first on the list.
I drove the car briefly, maybe a 1/2 mile. No miss at idle and no miss at part throttle. The engine still emits a fine black smoke and a smell that could choke you. While the power seems good, the performance is off compared the 2006 GTO I used to own. This is with new injectors and a new FPR. I can't drive any more until I resolve brake issues. Brakes are worse and car is very unsafe, will barely stop, soft pedal and full travel of pedal.
Could be leaking back through the pump, but if it's only losing 10psi in half an hour, I wouldn't think that would be any problem at all. Most of this sounds like you have an injector gummed up from sitting. If it ran fine and didn't miss when you first started it, I don't see how it could be much else, lines and tunes don't go bad in 4 years. LOL! I agree with Pop N Wood, I wouldn't be surprised it a lot of it went away after you've driven it some more.
This is a long shot, but do you have the large ground loops bolted to the back of the heads? There should be one on each side. Those are coil grounds and are critical. Is the engine grounded well? Big cable directly from the battery to the engine?
I suspect this is a tune or an electrical issue, not fuel related.
Andrew
I suspect this is a tune or an electrical issue, not fuel related.
Andrew
Just curious, but have you talked to Speartech about this? And if so, what did he say?
I think that is pretty good. I agree, I'm still thinking injectors are a potential problem.
After that bit is sorted, I would dive into the calibration and make sure things are good for a stock LS3. A tune can not fix a hardware issue, but an improper tune can make it look like you have a hardware issue.
I admit I am NOT a tuning expert, so this is only advice from personal experience and not a guarantee to resolve your problem.
I looked at your tune. If you are using an LS3 intake manifold with the stock LS3 MAP sensor, the calibration is incorrect.
There are a pair of fields that control what the PCM expects from the MAP sensor under Engine, Airflow, General. On that tab there will be two fields under MAP called: MAP Sensor Linear and MAP Sensor Offset. Yours is setup for a typical GEN III MAP sensor with 94.43 kPa and 10.34 kPa. An LS3 MAP sensor will read 128.13 kPa and -0.31 kPa respectively.
The injector data isn't quite right for a stock LS3 and the VE table is different but I really haven't gone much farther.
One problem is you can't straight compare the two because the TBSS PCM is built on an E67 controller while an LS3 is on an E38 controller. This means having two HP Tuners windows open at the same time and going field by field. Some fields don't exist in the TBSS file while others aren't in the Camaro file I was comparing.
Just the few things I mentioned could make your car drive like crap - if it runs at all.
Before you make any tune changes, save your original file and NEVER edit it. Then save the previous running (even if it was poorly) file and make changes to the copy. I use a date system and always copy off my original and save it in a different folder called "xyz original" so I know that is the very first read. This way if you really muck things up you have the previous version or worst case, the original to fall back on.
After that bit is sorted, I would dive into the calibration and make sure things are good for a stock LS3. A tune can not fix a hardware issue, but an improper tune can make it look like you have a hardware issue.
I admit I am NOT a tuning expert, so this is only advice from personal experience and not a guarantee to resolve your problem.
I looked at your tune. If you are using an LS3 intake manifold with the stock LS3 MAP sensor, the calibration is incorrect.
There are a pair of fields that control what the PCM expects from the MAP sensor under Engine, Airflow, General. On that tab there will be two fields under MAP called: MAP Sensor Linear and MAP Sensor Offset. Yours is setup for a typical GEN III MAP sensor with 94.43 kPa and 10.34 kPa. An LS3 MAP sensor will read 128.13 kPa and -0.31 kPa respectively.
The injector data isn't quite right for a stock LS3 and the VE table is different but I really haven't gone much farther.
One problem is you can't straight compare the two because the TBSS PCM is built on an E67 controller while an LS3 is on an E38 controller. This means having two HP Tuners windows open at the same time and going field by field. Some fields don't exist in the TBSS file while others aren't in the Camaro file I was comparing.
Just the few things I mentioned could make your car drive like crap - if it runs at all.
Before you make any tune changes, save your original file and NEVER edit it. Then save the previous running (even if it was poorly) file and make changes to the copy. I use a date system and always copy off my original and save it in a different folder called "xyz original" so I know that is the very first read. This way if you really muck things up you have the previous version or worst case, the original to fall back on.
I will have to take a look at the MAP values when I can get a chance.
Problems with flooding at work and no heat at my house is getting in the way right now. When I can get to it, brake work is probably first on the list.
