Hello Everyone! I new to the whole Corvette world. Always wanted one, finally was able to buy one. Made the mistake of buying it before looking at it, I know....... I had it shipped and have had problems since. Im hoping you can help me out a little bit and give me some advice on what to look for or check and where they are at such as grounds etc. So the car itself, 2009 C6 with 80k miles, Drives smooth and only mods it has are longtube headers with no cats and 64 pound injectors. Initally the service traction light and the check engine light came on and the maf sensor went bad, replaced it. it idles a lil rough but after reading other members posts assumed it was normal. at about 60-65 there is a small vibration that pulses in the steering every 2-3 seconds. Had the tires replaced, no clips on the rotors, no movement up and down on the rotors, road balanced, 4 wheel alignment done, its still there. I then got a P0300 code random misfire and I think its running rich. I hooked up my scanner and it showed it was missing on all cylinders mainly 7 & 8. I took of the valve covers, no broken springs, I replaced plugs, wires, coil packs, removed and cleaned injectors, swapped them around to see if the problem followed the injector and problem still persistent along with the other cylinders misfiring more at times than others. could it be running rich because of the injectors or headers or does it need to be tuned? Next step, im going to do a compression test go from there. Any other suggestions? I appreciate the help..

 

Bump for ya...

 

First of all the injectors are way too big. The Z06 has like 39 pound injectors stock and you have a L3 with headers with everything else stock you should at most have what the Z06 has which is 39 pound injectors. Now that 39 pounds is at 58 psi fuel pressure so if yours are 64 pound at the same pressure or at 43 psi then you got way to much injector. You may need a retune since you are making a big change to the injectors. I would go back to a stock injector and see what happens. The problem is like you said you do not know the history on this car and as these get older things / owners change with time.

 

Yeah seems very odd anyone would put that big of an injector on the car. I wonder if it was supercharged at some point and someone just took the blower off before selling it and never retuned it.

 

I agree, this sounds like the car was demodded. You should go through the car and make sure all the ground wires are tight on the engine block, as that can cause misfire issues, and check that it's not running a colder plug from previous forced induction. Also, make sure the battery isn't weak.

It would definitely be a good idea to go to a tuner and get it tuned, because at this point you really have no idea how it was modified or what it was tuned for.

 

Get some stock ls3 injectors and take them to the tuners

 

Thanks for all the replies, sorry it took so long for me to get back. So originally the plugs were ngk tr55 gapped at .35.....I replaced them with the factory iridium gapped at. 40...no difference. I did a compression test, I know leak down is better, jus haven't had a chance. I definitely think the injectors are not needed The brand is FAST. I can't find any thing that suggests it had nitrous or a a supercharger etc. The engine is relatively clean. Where are the major ground points at more of less?

Compression test
​​​​​1- 185
2- 200
3- 175
4- 200
5- 190
6- 200
7- 190
8- 190
I'm suppose to take it tomorrow to a corvette shop hopefully its something simple..

 

https://www.camaro5.com/forums/showthread.php?t=221700

Hopefully those helps. Make sure they're tight.

 

thank u! i went and checked and there are no ground wires on any of those points. Where do those wire run from? I'm going to try and see if I can find them.

 

thank u! i went and checked and there are no ground wires on any of those points. Does the c6 ls3 come factory with ground wires there? Where do those wire run from? I'm going to try and see if I can find them.

 

It's not easy finding a grounding location diagram for the LS3, so I wasn't 100% sure of those. I'll go look outside when I get a second at mine.

 

This was my first thought. I would bet that the previous owner had a blower or NOS on this car. May have also had a cam at one point. Probably also ran it hard or on the track. This is probably the same reason you had a failed MAF. OP -- go back to stock injectors as mentioned above. If you do the work yourself, be sure you dont lose the O rings. For the 7 & 8 cyls, are you dropping pressure?

 

Fixed! I took it to the shop and they hooked up the computer and he said all it needed was a tune. Runs perfect now! Yeah I wish I knew the history of it, would of made things way easier.

 

I'd be interested to see what the tune was before they tuned it.

 

how many misfires were you getting per cylinder? I have a similar issue but no code comes up ever. If i run the scanner, i get 2-4 misfires per cylinder at random and not all the time.

 

What is your car doing? Mine would misfire between 2-30 times within 20 minutes. Sometimes one cylinder would misfire 20 times then only 2 other times.

 

Now battery jus died. Crazy part was it was a acdelco from 2011! Never seen a battery last that long. I'm still trying to pin point this vibration that starts at 60. Pulsate every 2-3 seconds and stays the same as speed increases and goes away about at around 75. New tires force road balanced with the hunter machine along with a 4 wheel alignment

 

Misfires at idle mainly for a couple of times. Doesn't throw a code at all. I think I might need a tune update. I have changed spark plugs, wires, and move the coils around. Still misfiring.

 

Any injector can be made to work within reason... looks like they cleaned it up! Charged those are small injectors, but I don't know. I don't agree with the dude that assumed if someone had parts on the car it was beaten and treated inappropriate. I have my car charged and race ready and hit the drag strip once in 2 years... I street drive it, but 90% of the time to a kids school or grocery store... I wouldn't assume the car was beaten... clearly the guy wanted to save on tune money, and it's kinda a dick way to do that.

 

Stock or aftermarket wheels?