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Really new to the forum, found some great info already. Just bought a '12 Sierra 1500 4x4 Z71 extended cab. I believe it's lifted as well with 33" tires. It's my first truck in a really long time. Love the vehicle so far but I really want to get some grease on my hands and dive into the engine. I know basically nothing about performance upgrades (I've only done basic maintenance things) so I have a long road ahead of me. I'm planning on researching for several months at least through reading posts on this forum, articles online, watching YT videos, and reading the LS engine books I just bought. My plan is to install a cam in this truck to give it a bit more punch.
On to my stupid question. When you buy a used vehicle, how do you know what performance mods have been done to it? The previous owner may have already done the Diablo tune, installed a cam, etc. so if I do it too then I'll just waste my money. Can anyone give me some pointers on how to figure out the past mods? Thanks
Well, sound would be one way to tell if it has a cam, could also pull the valve covers and see if it has after-market pushrods which would be a good indicator of if it has a cam. For the tune, I guess the only way I would know is to get ahold of HPtuners and pull the tune that's on it and send it to someone that knows what they are looking at.
You basically can't know anything unless the PO can tell you exactly what they did. Pray that a diablo tune is not on there though because from what I remember that thing is locked on and unless you have the device to take it off you cannot.
You basically can't know anything unless the PO can tell you exactly what they did. Pray that a diablo tune is not on there though because from what I remember that thing is locked on and unless you have the device to take it off you cannot.
I guess it would be a good thing if the Diablo tune's already on right? I'll probably buy the Diablo tune anyway just in case. Or is it locked on forever unless somehow I get my hands on the original device? Crap I hope not.
Jealous of your LQ4 swap, read some great things about that motor. I probably should have bought an older truck lol. Would have opened up more engine swap possibilities. I'm pretty satisfied with the truck as is actually, just want a bit more power from it. It's also kind of loud so maybe a quieter muffler or something and I'll be set.
There are several cheapo tuners out there that lock on to the VIN, and you would need that exact tuner to remove them. If they used one of those, they screwed you by not including it, and its useless to them. The dealer can always flash it back to stock for probably $200-$300.
You could go get a dyno run done on it, and see if its right near stock.
You could put 87 octane in it, and go floor it on the highway. Should only take a few seconds to hear pinging if its tuned for higher octane.
If you post pictures of the underside suspension we can tell if its not stock.
If you bought it from a dealer, you can always contact them, and see if they will contact the previous owner to ask if they are willing to talk to you, or willing to tell you if anything has been done.
You could try and track down some locals at a meet or through here, and have some fun comparing.
You could get a GPS and check it against your speedo. You probably have to calculate in a different size tire, but if your gps and speedo are the same with bigger tires, then your speedo has been adjusted, and I would think you would have a "better than generic" tune (because it means they adjusted the gearing and tire size so your speedo is right). If its off more than it should be, they may have done the gears.
What reason do you have to think they have already done that?
There are several cheapo tuners out there that lock on to the VIN, and you would need that exact tuner to remove them. If they used one of those, they screwed you by not including it, and its useless to them. The dealer can always flash it back to stock for probably $200-$300.
You could go get a dyno run done on it, and see if its right near stock.
You could put 87 octane in it, and go floor it on the highway. Should only take a few seconds to hear pinging if its tuned for higher octane.
If you post pictures of the underside suspension we can tell if its not stock.
If you bought it from a dealer, you can always contact them, and see if they will contact the previous owner to ask if they are willing to talk to you, or willing to tell you if anything has been done.
You could try and track down some locals at a meet or through here, and have some fun comparing.
You could get a GPS and check it against your speedo. You probably have to calculate in a different size tire, but if your gps and speedo are the same with bigger tires, then your speedo has been adjusted, and I would think you would have a "better than generic" tune (because it means they adjusted the gearing and tire size so your speedo is right). If its off more than it should be, they may have done the gears.
What reason do you have to think they have already done that?
Yeah maybe I should take it to a GM dealership and see if they can flash it back to stock. Not sure I want to go back to the place I bought the truck. The salesman I bought it from was using the truck as his personal vehicle, guess he liked it. They didn't clean the truck or fill up the tank. Plus I found a box of condoms in the center seat compartment lol. That was pretty disgusting so I sanitized and cleaned the hell out of the interior.
Haven't really floored it yet but haven't heard pinging. I may try that this weekend. There's some rust on the undercarriage so I'm planning on removing it and painting it with Rust Oleum tomorrow so I'll take some pics of the suspension. Looks like some parts are brand new, maybe the dealership installed them.
Done what, the Diablo tune and cam? I'm just guessing because from what I read the stock transmission shifted slow. Seems like the transmission shifts pretty fast. Also the RPM idle fluctuates just a tiny bit. I've noticed it while stopped waiting for lights to change. Nothing serious or anything, just a few fluctuations. There's also a tiny amount of body shake (not sure what to call it lol) at idle on occasion so I was thinking maybe that's from an aftermarket cam.
I just emailed Texas Speed for advice/recommendations on what kind of cam package I should buy even though I just bought the truck two days ago lol. I think if I could just get a bit more power out of it I would be totally satisfied. Regarding a tune, couldn't I get a custom tune or off the shelf one and use whatever I have (stock or aftermarket tune) as the base and go from there? Or maybe it's better to get a completely stock tune then customize it.
04-16-2021, 12:25 AM
Stupid Question
