3.9 LZ9

[swathdiver]

Hello,

Does anyone have any information on this engine? Maintenance issues, things to look out for and such?

Just purchased a 2006 Pontiac SV6 that has this throaty motor in it, moves pretty good considering its weight.

Thanks!

James

[Joseph Upson]

Welcome to the forum, you're suppose to ask that question before you buy it, one of the best ways to find anything out of the ordinary is do a generalized search over the internet by entering the vehicle and then the engine, you may find a website specifically for the vehicle or any complaints noted so far. There may not be much if anything, although it's a fairly new engine it is from a long line and is probably put together very well.

This site will have some specifics from GM, click just above the picture of the engine and then to the left on the next page choose car engines;

http://www.gm.com/automotive/gmpowertrain/engines/other/index.htm

[swathdiver]

I looked, didn't find anything. I have another Montana with the 3400 motor and am aware of its strengths and weaknesses. Thought I'd get a post about the new motor rolling and see what turns up.

[CNCguy]

I looked, didn't find anything. I have another Montana with the 3400 motor and am aware of its strengths and weaknesses. Thought I'd get a post about the new motor rolling and see what turns up.

I see several positive things with the new engines.

Since you have a 3400, I'm sure you know that one of the biggest problem with them is the LIM gasket failure. They eliminated the passages on the LX9s and the problems that go with it.

The older motors tended to run hotter at the cylinders furthest from the water pump. Hopefully, that issue is improved with the U-flow cooling system.

GM also added oil squirters to each cylinder which should reduce piston wear and help to get rid of piston slap.

LX9s also use powdered metal rockers that are 16 grams lighter than previous models.

Seems like good things to me.

[swathdiver]

Motor crapped out on me tonight while merging onto highway. Was turning around 5500rpms felt a jerking motion then the motor quit and I pulled it over. Just turned 1000 miles today. Tried to restart and heard clicking sound and it shut off, check engine light was on. Towed to the dealer after closing, will post info after repairs and get the car back. 2006 Montana SV6.

[Joseph Upson]

Motor crapped out on me tonight while merging onto highway. Was turning around 5500rpms felt a jerking motion then the motor quit and I pulled it over. Just turned 1000 miles today. Tried to restart and heard clicking sound and it shut off, check engine light was on. Towed to the dealer after closing, will post info after repairs and get the car back. 2006 Montana SV6.

That's my biggest fear about ever trying to do a new generation PCM swap along with a new generation engine, I would have to learn a new system just to keep it running if a problem like what you are having now occured so it's easier for me to apply an older system to a new engine. Sorry to hear you are experiencing that kind of madness with a new vehicle. Do keep us posted.

[Joseph Upson]

So what did the problem turn out to be?

[swathdiver]

Not sure exactly. The service manager told my wife that the wiring harness and the body control module were faulty. The harness causing the motor to cut out and the BCM causing the lights not to respond to the light sensor. They ordered new ones, got them in and discovered that the main computer would not recognize the part number of the new BCM. He told he was waiting for an e-mail from GM to update the software to accept the new BCM. For a rental they gave us a '07 Uplander with the same motor, much more spunky then mine btw, I asked my wife if she tried to get them to take the parts off of the rental and pop them in the SV6 so we could get our ride back!

I'll plan to talk with the mechanic in person tomorrow morning sometime.

[Joseph Upson]

Sounds scary to me as well as like the GM dealership does not have the necessary goods to take care of it right away. Make sure you stay on top of it.

[swathdiver]

Yeah, I thought it kind of odd, however the motor is new and they're not making the van anymore. However, the motor used in other cars like the G6, that's why I'm going tomorrow.

[swathdiver]

Update

Finally got it back. First mechanic didn't know what he was doing, he replaced the BCM then screwed all the other computers up, looked like a deer in the headlights when I quizzed him as to the problem. I sought out the most experienced mechanic at the dealership and he took on the task first figuring out what the gut did, reprogrammed all the different computers (called a burn) then went to work looking for the source of the stalling problem. This turned out to be bent pins on the coil pack module connector. So far so good, motor feels like it has more power then before.

[CNCguy]

Good to hear that you got it back and it was only an electrical problem. But it's ridiculous that it took them so long to fix it. I guess there is going to be a learning curve for the mechanics on all the new electronics.

[Joseph Upson]

Good to hear that you got it back and it was only an electrical problem. But it's ridiculous that it took them so long to fix it. I guess there is going to be a learning curve for the mechanics on all the new electronics.

No learning curve issue at all, some of those guys don't have a clue even after they've learned the system, they don't follow the diagnostic flow chart, or can't because as I stated earlier, some of them don't have a clue. I had a guy working in the shop I use to work for that came to me saying that he needed more fuel hose for the replacement mechanical fuel pump (exact match of the one he removed) I had just given him to install. When asked he said he hadn't cut the hoses and that's when I decided to go take a look.
I am not lying about this, he took the old pump off and couldn't figure out with adequate lighting that he was attempting to put the new one on UPSIDE DOWN and I asked him to take a good look at it before explaining what the problem was. The reason this story is significant is because he left us for a job with the Ford dealership.

And that's why I know so much about car repair today, it costs the same amount to have an idiot work on your car as it does a real pro, trouble is you have to pay first to find out the difference. So now I take the cost of a repair and buy the tools to do it myself.


Now CNCGuy I need you to update the 3900 thread specifically with some confirmation that I will not have a serious problem with running the engine with the VVT disabled so I can get the ball rolling on purchasing one to install in place of my 3500 which is almost ready to be swapped in. Ryan said running with VVT disconnected in the Northstar = bent valves, however it has separate intake and exhaust cams so that would be feasible where the 3900 does not so where ever the int lobes go the exh lobes follow. I believe this engine has the potential for astronomical output given the resent numbers posted by less efficient 34 and 3100s at just 10 psi on tiny intake valves and half a litre or more less displacement.

[CNCguy]

Joseph.... Nice story. I know exactly what you are saying about the competency of mechanics since I have worked in auto repair, machine repair and machine shops for over 30 years. Every industry has it's share of idiots. I was just trying to not be critical or make assumptions.

Still haven't found out who borrowed my spring compressor but will try to round one up so I can get you some measurements. The N* must operate completely different than the 3900. The actuator on a 3900 has a lock pin in it that physically locks the actuator when it isnt operating. It also has a spring that returns it to the locked position. I assume it locks in a position comparable to a non VVT application in the event of VVT failure. I am planning to use that position as my starting point to degree in the cam when I make the VVT eliminator.

[farmerz24]

guys, i dont understand why you would want to eliminate the VVT. I mean, it will boost power if used properly. Recent discussion indicates a controller box can and had be made, so why eliminate this system altogether???