Hello everyone. My name is Jeff. New to this site, but have been on other forums as I used to own a Grand Prix for 6 years. Looking at buying a 2005 Bonne GXP fully loaded with 55K for 13,900. Good deal? Is there any known issues that I should check for before buying? How is the N* engine in these things? Pretty reliable? Any info here will be greatly appericated. Thanks!

GXPVenom would be the one to chat it up with. If he doesn't step into the thread you can PM him.

A little pricey. KBB for private party is
Excellent
$11,765
Dealer prices always a bit more. Seen some go for lees, but cant comment on condition of them. I guess it depends on how you feel about the car, is it cherry? Northstars are pretty reliable. But when they go, they go. Not alot can be rebuilt on them. Our in particular has some motor mount issues and oil line leaks. You prolly wont see the 200-300k endurance of a 3800 or 305. They seem to cripple up after 150k give or take. Although we do have a member I havnt heard from in awhile that was at 155K and still purring the last I heard.

The car is actually black, and its in pretty good shape from what I can see. I've been looking around and there'* not too many after market parts for these cars. Is that right or am I just looking in the wrong spots?

The biggest problem that I know with the N* is the head-gasket issue.

So unless you are willing to either pay for that fix, or rip apart the engine once you get it to fix the head gasket and the bolts that attach it, I would stay weary of at Northstar for reliability.

FWIW, a dealer / mechanic will charge ~18 hours labor for a head gasket change in that car, usually you have to pull the motor just to do it!

Maybe look around for some Grand Prix GXPs, and have the LS4? Unless your budget really doesn't allow that.

Also keep in mind that if your looking to mod the engine, your really limited on the N*, the PCM is locked so you can't even change the tune.

The only aftermarket parts you can really get for our cars are for the motor and thats only for the 3800. The Northstar in the GXP isn't a modifiable engine other than NOS. If you're looking for aftermarket body and interior stuff let me save ya the time and tell ya that they don't exist. Nobody made custom hoods, body kits, etc for the Bonne.

And how big of a problem would you say that is? I mean if I'm buying a car and have to worry about my headgaskets going out everyday, not something I'm looking forward to. This will become my daily driver and I drive about 350 miles a week. Not going to be cool if the headgaskets go out and I'm going to need to pull the motor to change them.
Might be holding off on it and looking for a grand prix gxp then. I know those motors a lot better then I know the N* ones anyways.

Ok, just to clarify, the head gaskets are not the MAJOR issue. The head gaskets are the result of a major issue. The real problem with the Northstar is that the material used in the blocks is overly porous, so what happens to a lot of them is that the studs holding the heads on start pulling out of the block, and then that takes out the head gasket.
The problem was very common in the pre-2000 models (mainly Cadillac). In 2000 they made some revisions and again in 2004. They SHOULD be a lot better in the GXP'* (2004-2005), but there are some indications that it is still happening.

Yep, Caddy went to "squeezecast" technology after head gasket/headbolt troubles of the "90'*" And that has seen several improvements since 2000. A couple of things that seem to have been resolved is the mysterious oil shortage(block seepage) and head bolt zerks giving(head gasket failure and head warpage) There will always be exceptions to this because of driving habits/mods and the fact you cant stop galvanic corrosion totally. Any time you put iron against aluminum, in time, it will happen. Regardless of how hard you anodize the aluminum, or bolt sealent you come up with. But in all the newer N*'* reliability is very good haunted by the horror stories of the past still lingering with all the misinformation spread. But when they go, they go. Or your paying more than its worth to fix.

Nitrous isnt the only mod.

Your could gain some by using Jet Chips controller (its piggybacks the PCM) and use a unrestricted "tuned" MAF (altered Maf reading) Jet Chip and Granatelli both seel them. But they only change parameters a bit. Not going to get butt dyno results.

A second option is a Holley Commander PCM $1000 (CHRFab'* Fav) or a Marelli Magneti PCM $2000 (MalletCars Fav) But with both of these have sensors that have to be "fabbed" to fit the engine and takes an experienced professional tuner with a dyno. They dont come with "canned tunes" and the fabbing/tuning could go over the PCM cost easily. And again, tuning isn't everything, your just tweaking parameters.

Several people have mentioned writing around the PCM programming including a recent one who is up in the God'* Country portion of Canada, so you never know. The engine is so limited in recent years (GXP and the Lucerne Super)