# New Owner of a 5.7 GTO need advice



## RKLamb (Jan 27, 2011)

Hello guys well after years of driving imports I decided to get one of the hottest american muslce cars to come out in ages the GTO. Well I got it on a pretty good deal at 70k miles, new tires, new clutch, and it looked and ran great. I drove it for 8 straight hours home with no issues. In fact I actually drove almost 400 miles on a single tank of gas and was averaging 28-31 mpg. Well that is the good. Now since getting it home I have discovered some issues I need to address
1. The drivers side window comes down when it wants too
2. My horn does not work
3. It has an aftermarket radio that I hate
4. It came with a diablo tuner K&N cone filter and a seeemingly loud flow master exhaust. Everyone else loves it but I just gave up a Lexus IS so Im not use to hearing so much while Im riding. Lol
5. How much quieter would the car be if I switch back to stock exhaust and what would I lose by doing so?
6. I get excellent gas mileage on the highway but Im only getting like 10.5 mpg in the city. I thought these cars especially the 5.7 do 18 in the city. Maybe its the way the guy has it tune.
7. Finally if you wanted to spend 3000 in upgrades would you turbo it or go another route.
8. I also hear a tap or knock from the rear anytime I am about to pull off it could be brakes seeing that it needs pads all around and rotors on the back.


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## Ls1young_goat (Feb 3, 2011)

do u have big rims in the back? or big tires ? because they might be hitting
also if ur horn isnt working check the horns see if there connected because mine were not connected n as soon as i plugged them in it worked again also my gto does around 14 or better in the city n i dont drive it to be efficient so check your tuning


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## RKLamb (Jan 27, 2011)

Ls1young_goat said:


> do u have big rims in the back? or big tires ? because they might be hitting
> also if ur horn isnt working check the horns see if there connected because mine were not connected n as soon as i plugged them in it worked again also my gto does around 14 or better in the city n i dont drive it to be efficient so check your tuning


Yeah the tires are 18s I believe 235/40/18 thats not big compare to those 265s I wanted to stick on it. Lol

I will check out the horn and the fuses for them over the weekend. Now as far as the gas go. I filled the tank up on sunday and I am at a half a tank now and Im just riding around town. Open road no problems it barely moves. When I check my mpg gallon tab its saying 10.5. Now on that long drive I had it said 26 average. Now I do live in a small town with a lot of lights but 10.5 is lower than those gas gussling Nissan Titans.


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## Ls1young_goat (Feb 3, 2011)

i have 18s as well but mine are 275/35 so im sure the 265's will fit on urs only thing is i have to get my wheel wells rolled because the tires hit when i have a full tank of gas n passengers lol and 10mpg isnt right =\ even with stopping n going


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## FastFrank (Jun 12, 2009)

RKLamb said:


> Hello guys well after years of driving imports I decided to get one of the hottest american muslce cars to come out in ages the GTO. Well I got it on a pretty good deal at 70k miles, new tires, new clutch, and it looked and ran great. I drove it for 8 straight hours home with no issues. In fact I actually drove almost 400 miles on a single tank of gas and was averaging 28-31 mpg. Well that is the good. Now since getting it home I have discovered some issues I need to address
> 1. The drivers side window comes down when it wants too
> 2. My horn does not work
> 3. It has an aftermarket radio that I hate
> ...


Welcome to the 04 goat club.:cheers

There are a few things you need to know about your car. First of all, there is a known potential problem with the BCM wiring harness rubbing against something behind the glove box. This would possibly be your window problem as it might be shorting out wiring going to the BCM. If you find that your horns are unplugged (they are mounted in the front bumper cover, near the fog lights), the previous owner may have unplugged them because they can sometimes honk on their own. This may also be caused by the wire harness behind the glove box.

The aftermarket stereo you'll have to decide what to do with, sorry.

As far as the exhaust goes, does it have aftermarket headers or stock exhaust manifolds? If it's stock manifolds with aftermarket exhaust, you won't lose much performance going with the stock exhaust. If it has long tube headers you will lose some performance, especially if it's tuned. 

You can definitely hear the stock exhaust while you are driving, but it's pretty quiet for a muscle car. I thought it sounded pretty good when I had mine stock.

$3000 would be a good start for going turbo or supercharged, but it will cost quite a bit more to get it done from what I've read on here. Save up more money if you want to go with forced induction.

It's normal to occasionally hear a clunk in the rear end, but if you are hearing it a lot you may have rear end problems, which has also been reported with these cars. You might want to search on it if you really want to find out.

City mileage is not sounding very good for you. I would expect it to be closer to 15 or better to be honest. But it really depends a lot on how you drive it. Try driving it like grandma and see if it is any better.


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## RKLamb (Jan 27, 2011)

Yeah it has stock manifolds but when you hear it you would swear they were'nt. I have had guys in Camaros come up to me and ask what motor do you have and when I say LS1 they say, mine sounds nothing like that. Lol. 

Electrical problems so far have been the drivers side window, the horn, and I hitting the T/C button but I dont see where it is saying it is off.


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## Lukemo2 (Apr 13, 2010)

*Hello!*

When you turn off the T/C, it will say "TRAC OFF" on the digital display below the speedo and it stays there the whole time you have it off. My car has had some strange electrical hiccups, but nothing permanent. Just wierd stuff randomly; like the gauges going all crazy on start up and randomly not working. Twice I've had the car tell me it was overheating right after I started it up. For me, both of these situations were corrected by turning off the car and restarting it. 

I have the stock exhaust on mine and I think it sounds great. Its throaty but low key during normal driving and sounds awesome at wide open throttle (in my opinion). I love it. 

I get 15 - 18 MPG in town and about 23 on the highway. I've had my GTO for a year and a half and the mileage has been consistent the whole time.


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## RKLamb (Jan 27, 2011)

Well I guess it must be the tune that the guy used with that diablo. Right now if you check the actual screen that gives you your overall mph mine says 10.5. Also I been hitting that t/C button and I have yet to see it say it was off. Maybe something is up with my wiring in the center counsel.


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## jpalamar (Jul 22, 2008)

Take it back.


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## RKLamb (Jan 27, 2011)

jpalamar said:


> Take it back.


LOL I thought about that but I have had 300zxs in way worst shape and hey it runs like a champ other than that.


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## RKLamb (Jan 27, 2011)

My rule has always been on any car if I can drive it home Im good. LOL. I had a VW corrado that would make this GTO seem like a Lambo. I ended up buying new rims, new tires, brakes, abs cylinder, supercharger, replacing all hoses and belts, radiator, and all the wiring under the dash in the first three months.

I had a 300zx for 5 years and drove it for about a month's worth of time total. The first engine threw a rod, the second one was sabotage by a mechanic who started working on it then stop then asked me to sell it to him since it was not running. The third engine has bad rings and had to be rebuilt. After that I just said screw it. And that is why I am riding american muscle today.


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## jpalamar (Jul 22, 2008)

$3000 in mods: $650 for Hot Jet coated Pacesetters and mids, $350 for a new shifter, $500 tune, and $1500 suspension(you have 70k miles already so its probally already blow if it hasn't been upgraded yet).


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## RKLamb (Jan 27, 2011)

jpalamar said:


> $3000 in mods: $650 for Hot Jet coated Pacesetters and mids, $350 for a new shifter, $500 tune, and $1500 suspension(you have 70k miles already so its probally already blow if it hasn't been upgraded yet).


Yeah I was going to get a subaru but we all know how they dog those. Yeah that looks like a good list. I am not really worry about going faster or HP as much as prolonging the life of the car. So suspension was at the top of my list. 

Update. Alright maybe this is why my gas mileage sucks. In my town I can barely get up to 4th gear. Its that small and that congested. Most of the time I am riding in 3rd barely making into 4th almost never getting to 5th. 6th is basically impossible riding around here. Now if I look at the display on the right that gives instant MPG it is ranging from 18-23 in the city, but when I look at the one on the left that just says MPG it like 9-10.5.


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## AEgto (Dec 6, 2010)

i can ride around in my small congested town in 4th i have taken my car down to 18mph in 4th i get 14 and my cars supercharged


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## RKLamb (Jan 27, 2011)

AEgto said:


> i can ride around in my small congested town in 4th i have taken my car down to 18mph in 4th i get 14 and my cars supercharged


Wow that is good on any level. Well I reset the ecu to the original tune with the Diablo and the traction control now works. So I think I will ride around with a stock tune for a while to see whats what. Now as I say I get good mileage on the screen on the right that says instant mpg, normal numbers, But the one on the left with the overall average has not shown anything higher than 10.5 since I got home. On the highway it showed a overall rating of 26 the other day.


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## dustyminpin (Jun 19, 2006)

I have the 4 speed auto. When my car was new/stock, it averaged 18 mpg, that's highway and city driving averaged in to one tank of gas. When I got my headers, catback, and cai along with a custom header tune for my Diablosport Predator, I shot up to 20 mpg, with 21.5 mpg on the interstate with the cruise set to 80. 

After my heads, cam, intake manifold, torque converter, etc. swap, I dive bombed to 12-13 city, but am still around 17-18 highway. With city/highway driving averaged together on a tank of gas (according to the computer) I'm averaging 14.5 on 93 octane. Can't run lower due to the tune. I know that sounds horrible. 

But the car... it doesn't SOUND horrible, clackity-clackity-clack he he he. I wouldn't change anything. Got the all motor bug now. Putting on my 102mm throttle body, maf, and cai next Wednesday, then setting sites on Texas-Speed's forged/balanced 402 stroker kit and a bigger cam .


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## AEgto (Dec 6, 2010)

see mine says 14 but i dont know how to keep my foot out the gas :rofl: the supercharger sounds so nice so i like to here it arty:


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## dustyminpin (Jun 19, 2006)

Supercharger whine is badass. My buddy at work has a Lingenfelter C5 with a Maggy, sends shivers down my spine...


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## 2006KJ (Jan 3, 2011)

check the horn relay or fuse for the horn not working. Stock exhaust will quiet it down. maybe the window switch is bad and shorting out?


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## RKLamb (Jan 27, 2011)

Yeah I would love to have a supercharger. lol. Yeah it is funny I am riding around and I have folks with camaros and Trans am asking me what engine I have and I say just a ls1. Then they say hell I got the same engine and its sounds nothing like that. Some think I got more than a flowmaster exhaust. I dont know because the guy i bought it from dont know since it was all done before he bought it.


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## Indecision (Oct 24, 2010)

dustyminpin said:


> I'm averaging 14.5 on 93 octane. Can't run lower due to the tune.


Stock cars need premium, I would hope a tuned one would still need it.


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