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Grand Prix GXP preventive maintenance tips

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Grand Prix GXP preventive maintenance tips

Old 02-20-2018, 03:02 PM
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Default Grand Prix GXP preventive maintenance tips

I wrote this long reply to someone on Facebook, and since I spent so long on it, I thought I'd share it with the community. If anyone else has tips, be sure to let me know.

My post:

I have a 2006 GXP I've had since January 2009 and have a ton of tips. I bought it at 26,000 miles and it currently has just under 70,000 miles.

The fuel filter isn't an inline one, it's in the fuel tank on the fuel pump, so it isn't something you can really swap out all that easily if at all w/o changing the fuel pump.

There's a little tiny Displacement on Demand filter somewhere on top of the engine you can replace for about $3 if I remember right (yeah, you can buy it from a GM dealership for about $3). I did this several years ago, and so I don't remember where exactly it is, but mine wasn't even dirty in the slightest. I went ahead and changed it though.

If it still has 4 cylinder mode (DoD or AFM) enabled, I would recommend disabling it via a tuner. I use Diablosport InTune which I bought new several years ago for about $300. If you get that one, it makes you select a transmission tune, but after installing the engine tune (91 octane no DoD) you can click the X on the transmission tune. I drive exclusively in manual/tapshift mode so I definitely don't benefit from their transmission tune.

Learn to drive in manual mode. Maybe it's just luck, but at nearly 70,000 miles I don't have any transmission issues. I did a poll one time in a different GXP group (that only got around 15 votes though...) and everybody who voted who has had to replace their transmission drives exclusively in Drive. I like manual mode because I can downshift to slow down and I don't have to suffer through the awkward, sloppy shifts that Drive gives. Since we only have 4 gears it's a real pleasure to use... it's not a chore like some of the modern 7 speed and 6 speed automatics.

Always carry a quart of 5w30 oil in your trunk in that little cargo net area. You'll want to keep an eye on your oil level when your DIC says it is below 70% oil life remaining. Even with DoD disabled, I still keep an eye on it. With it enabled, some people go through several quarts of oil between oil and filter changes. Our cars consume oil.

I use Lucas Synthetic Oil Stabilizer in my oil. When I get an oil change, I wait until about 80% oil life remaining, I check the dipstick, and if the level is low enough, I add half a quart of that to my oil. It keeps the rockers quiet, which can chatter a bit, particularly in cold weather. It's around $17 a bottle.

Occasionally I use Lucas Complete Engine Treatment in my oil and gas, usually only if I find it on sale, and only in my oil if I haven't already used Lucas Synthetic Oil Stabilizer. It's around $10 a bottle. You can only add a few ounces to your oil, and only a little under a full bottle to your gas tank. It's supposed to clean and lubricate things. I only drive a few thousand miles a year and DoD was enabled until around 2014, so I like to try to make and keep everything clean inside.

Tell oil change (and other places) not to check your air filter if you have the factory OEM air box. It's basically impossible to correctly close it without removing it from the car. So you'll end up spending 30 minutes removing the entire thing from the car if someone decides to open it and try to look at the filter. I have a sticker on the black bar over it that says not to check it, that I maintain the air filter myself.

For transmission fluid changes, don't ever let anyone flush your fluids. The transmission pan needs to be removed, the filter needs to be changed, and I always pay the extra ~$60 for a new pan gasket. Never let anyone flush your transmission fluid! Change the fluid and filter every 15k to 20k miles if you regularly hit 200+ degrees.

Get a transmission fluid cooler that you zip tie to the front of the radiator if you regularly go on road trips or long commutes in your car. You need to prevent 210+ transmission fluid temperatures for prolonged time periods. I only have a 3 mile commute to work, so I don't have one. When I was working 16 miles from home though, I was heavily considering it, because the 45 minute drive was enough to get me to 190+ every time. 180 is considered operating temperature if I remember right, but 200+ is bad.

Coolant has to be changed every few years. DEXCOOL (orange coolant) lasts 5 years so get it changed every 4 or 5 years. If you or someone has converted to green coolant, you are going to have to monitor it more heavily. It has to be changed every 2 or 3 years. Green and orange do not mix. A little orange added to green coolant will produce what looks like peanut butter (after an unknown amount of time). I had to have the radiator in our '95 Z28 removed and replaced and all the hoses flushed with water because an oil change place (or dealership or other shop) must have topped up my green antifreeze with DEXCOOL, because it fowled and became peanut butter. It wouldn't go away and kept coming back. Personally, I recommend sticking with DEXCOOL forever and just make sure you get it changed every few years. It is easy to monitor on our GXPs since the overflow reservoir is so easy to open the cap on and look at.

I have some other good preventive tips as well.

The spring in the Head Up Display can break, so don't play with moving it up and down a lot. Find a setting you like and stay with it.

The front speaker in the dash has a habit of going bad. Someone told me about that in 2009, and so it's really easy to keep safe. You just slightly put your stereo's balance to the rear of the car. I don't remember the setting, but it's just barely off the center, balanced setting. It'll still sound good too.

I don't know about other owners, but when my wheels are dirty, my car drives crappy. I'm sensitive to differences, and everything just seems wrong about the way it drives when the wheels and struts are dirty. Ironically, I was complaining about my GXP feeling unstable and unsettling when cornering a month or so ago, and washing the car got rid of that. I'd love to be able to tell you what the problem is or how cleaning helps it, but I actually don't know.
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Old 10-15-2018, 02:40 PM
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Thanks for the tips... Just picked up a one owner 06 GXP and after I get rid of a couple codes and throw on an external tranny cooler I will have her out..

Retired -
1970 Orbit Orange GTO Judge
07 Antique Beige Grand Prix 3.8
06 Stealth Gray Grand Prix GXP
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Old 10-16-2018, 02:16 PM
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I forgot I made this thread. Glad to finally see a reply to it

Here's an update:

Head Up Display spring fix - this isn't preventive maintenance and can't be prevented. But it can be fixed pretty easily with a LOT of time and minimal tools.

The spring in my always garaged, 72,000 mile 2006 GXP's HUD finally broke off the plastic it was attached to. Diagnosing this is super easy. If you know your HUD was working the last time you drove, pretend you're as tall as an 8 year old and try to look at the windshield through the steering wheel--in other words: get low and look straight up. You'll see that your HUD didn't burn out, it is just displaying straight up. Your spring broke off. I used these directions, even though they weren't perfect:

I literally fixed this last weekend, so it's very fresh in my mind. I ended up printing the website after modifying the code of it so the images would print big. I've attached a PDF of that to this post. Here's the list of my comments about what was wrong or what I experienced:
  • Overall, the biggest problem is it says it takes like 3 hours. Including fixing the HUD and putting everything back together, I spent 12 hours or more over a Saturday and Sunday.
  • Step 4 mentions you need to disconnect 1 wire. You have to disconnect 2 wires. 1 goes to your passenger airbag light, the other goes to your DIC.
  • There's no reason whatsoever to do Step 6, just unscrew the screw in front of it.
  • I don't understand why step 7 was listed, I don't think it was necessary but I did it anyway.
  • Step 11 is horribly difficult. I used a Lowe's plastic card and Autozone plastic reward card to help lift the dash. Those clips are no joke. They are the same type as on the side dash panel in step 5. I've seen the official GM service manual for removing the HUD and it says not to pry with a screwdriver or anything else metal. It says to undo the 2 clips on the right and left of the HUD portion of the dash first and then the one in the middle of the HUD (closest to your face) which is total BS. I think you're going to want to go left to right a little at a time. Pertaining to the HUD portion, start on the left, move to the middle, and then the right. Or vice-versa. I cracked my dash popping the clips out, so that sucked. But to complete step 12, I had to get my fiance to come over and help me. I struggled with it by myself for almost 2 hours. You need someone with very small hands to turn the security light and light sensor a 1/4 turn. And you need someone with very small hands to push down on the plastic that is under the dash while they pull the dash upward and out. In my case, the foam rubber was stuck underneath the windshield and a part of it had to be torn off to get the dash out. It took over an hour, maybe 2 hours to try to get this out together. I ended up with 1 large crack in my dash, 2 small cracks, and 2 broken pegs. The dash is made of ABS plastic, so you can repair it with a chemical weld. This product isn't made anymore, but it's called Ambroid ProWeld. I used it to nearly flawlessly repair the cracks. You cannot glue ABS unless your glue is specifically made for ABS and you shouldn't try to Fiberglass it or anything like that. Ambroid ProWeld isn't made for using as a glue, it's made for causing ABS cracks to chemically seal themselves, so the pegs didn't get glued on well. I should have gotten some ABS glue for plumbing or something... but I didn't want to go to Lowe's to see if they had ABS plumbing glue. Also, FYI, Ambroid ProWeld is a liquid that you brush on like nailpolish, except it is as thin as brushing water and very toxic. You have to be well ventilated outside to use it.
  • Step 12 is simple. So are steps 13 through 16.
  • Step 17 is tricky only because of how tiny this plastic piece is. Your margin for error is very small. This piece is made of POM, which is a type of high tech plastic that (based on what I read) is basically very difficult to repair. It reminds me of Lego plastic. So anyway, repairing the plastic in a reliable way is impossible. You can't super glue it or necessarily have faith in epoxy. It may not stick, because this plastic is meant to be hard to stick to. So you're going to have to drill a tiny 1/16" hole next to the broken part, but there's a bar behind it, so you have to get it placed exactly so or you're going to drill through a structural part of the piece. I put the piece in my vice with rubber grips on it and drilled it after etching a tiny dent in the piece with a sharp nail so the drill bit wouldn't slip. And because the worn/broken area was so large and it made me so nervous, I went ahead and repaired the original area with epoxy just to put my nerves at ease and maybe provide some structural strength. It was too small for me to epoxy a small metal washer (which I didn't have) around the hole, and I didn't have faith epoxy would hold it, so this ended up being a repair that I hope I get another 12 years out of before the spring eats through the hole I just made too.
  • Steps 18 through 20 are super easy.
  • Putting everything back together took 4 hours for my fiance and me to do. About an hour was spent trying to get the light sensor back in the dash though. The red security light was bad enough, but my God, what a horrible experience. I'd recommend a long pair of needle-nose vice-grips for holding the sensor and trying to turn it. I didn't have a pair that was long enough, so it was difficult. I can't tell you how hard this was to do. We finally resorted to what I hoped to avoid and I pushed up on the dash toward the windshield while my fiance used her small hands to get the sensor into the hole and turn it. We ended up breaking the 2 pegs off I attempted to glue on and recracked the big crack I fixed earlier. And after that was done, the act of snapping the dash back down into place reopened that large crack a lot more. And the gap is large enough that it can't be pushed back together for another dose of Ambroid. But at this point, I don't care. I'm glad my HUD works again. The rest of the reassembly is pretty simple.

Last edited by Brangeta; 10-16-2018 at 02:36 PM.
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Old 11-06-2018, 12:25 PM
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I wonder if the oil consumption was an issue depending no how the engine was used/abused from day one? I have an '07 with 68k on it and uses no oil whatsoever. Even with DoD enabled. Car came from Victoria, British Columbia, which has a lot of retired folks, so car didn't seem to have been abused at all. I know a lot of people on this forum have oil issues, and some were recalled depending on usage, so who knows. Luckily, mine seems far.

I also have a Diablo InTune3 Platinum to disable the DoD, and I'm currently running the 94 tune with hard shift transmission programming. I seem to think the shift change also changes the shift when using TapShift, but I could be wrong in that...I've only tried it a couple times, and never really used it much before.

Thanks for the 'heads-up' on the HUD!

Last edited by BlackApex; 11-06-2018 at 12:49 PM.
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Old 11-07-2018, 05:46 PM
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Writing this quickly before I leave work... Is it possible that your GXP had the TSB (technical service bulletin) taken care of for the oil consumption? There wasn't technically a "recall" I don't think. GM just created a new part... like an oil pan... (or something), but if you wanted it, you had to pay to have it done. I never paid to have it done, so I don't have it. My GXP has gotten bad gas mileage the entire time I've owned it since January 2009. Both with DoD enabled and without. Without I average 12.8 mpg. With it, I don't remember, as it has been many years since I have used it. I'm currently at 72,000 miles. I've consumed oil the entire time, but back in the day, I didn't know it, until I got my first "low oil" light on a road trip.

I love Tap Shift. It's one of my favorite things about the car. And unlike all of the GM cars from the last 10 years, our steering wheel buttons actually make sense. I hate all the GM steering wheels from the last 10 years with their horrible "seek" up/down switch on the right-hand side of the steering wheel. Garbage.
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Old 11-08-2018, 07:32 AM
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It's possible the bulletin was done, but I wasn't told about it, so I assume not. I'm about to change the oil before storing the car for winter. In 5000 miles, the oil hasn't dropped at all on the dipstick.
I'm also averaging 20.9MPG right now with city and highway driving, and tuned to 94 octane. And with the tune, I tend to accelerate faster now just for the fun of it. I don't floor it, but driver it quicker than before I tuned it for sure. Odd you're getting such bad mileage...unless you're all city driving.
And...I'm actually running 255/35ZR20 Continental ExtremeContact Sport tires all-round, so that would probably not help my mileage any being a sticky tire...obviously I'm not hard enough on the throttle...

Last edited by BlackApex; 11-08-2018 at 02:39 PM.
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Old 11-25-2018, 12:26 PM
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Nice to see people taking meticulous care of there car. I'm an original 06 owner and don't ever see getting rid of the only at about 70000k and only drive in the summer.
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Old 11-26-2018, 06:50 PM
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Originally Posted by BlackApex View Post
Odd you're getting such bad mileage...unless you're all city driving.
I'm pretty heavy on the throttle and almost exclusively city driving in Dallas, so my gas mileage is partially my fault. Most people in Dallas drive aggressively. Moreover, in manual mode (tapshift), in order to get a smooth upshift from 1st to 2nd, you need to be over half throttle, or you'll get that forward motion (with your body) that driving in drive will give you on that upshift. You know... where your head nods forward as the acceleration briefly turns to deceleration. I don't really pay attention anymore; shifting into 2nd is like second nature, but I suppose it's a little over halfway to the floor to get a nice shift. I've been driving my GXP since I got it in January 2009, nearly the entire time in only manual mode. The 2nd to 3rd and 3rd to 4th upshifts don't care as much about how hard you're pushing the gas, they are pretty smooth no matter what. If I remember correctly, the gear ratios for 3rd and 4th are barely any different from each other. But 4th is only for shifting into over 50 mph unless you're just throwing it into 4th and coasting to a far off red light or stop sign. If that's the case, I'll do that anywhere over I guess 40 mph and just let off the gas completely as long as I'm not going uphill. And, of course, 2nd gear doesn't come close to redlining until around 90 mph, so if I'm getting on the highway from a red light, I just stay in 2nd until after I've hit 60 or 70 mph. By no means do I downshift to 2nd from a speed of like 70 to accelerate. I'll go down to 3rd if I really need to pass someone or drive defensively, but it would be unsafe to drop to 2nd gear from that speed in my opinion.

The owners manual is surprisingly helpful in teaching a person how to shift in manual mode, but it really comes down to practice and experience. It's not difficult by any means, but shifting smoothly will take at least a few months of experimentation.

Gee... I got off on a tangent. Oh well, I had fun typing it.

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Old 12-06-2018, 12:33 AM
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From a dead stop in tap shift, you can start in 2nd gear.

And once the 5.3 receives a tune, a better transmission cooler, a deeper transmission pan, an electric exhaust cutout, a turbo, an intercooler and preferably also more or less a meth injection, you find you gain access to a much safer and broader range of available power and control when compared to the stock car. 2nd gear becomes more or less home, if you want it to be.

Ultimately you end up with a decent street car. One that can use just one gear, second gear, to consistently run 5 second 0-60 times and reach 90 MPH top speeds.

These transmissions suck? So why shift? Turbos solve the worlds problems.
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