Sean Goodwin

edit: think this was posted in wrong section, meant for external, if it needs moving plz feel free.

Hey guys, really need your help figuring out this seriously annoying problem I am having with this new beauty of a car I purchased. So I will tell you all the story and hope to god you can all help me out somehow. I need this figured out!

Car was purchased 13,600 miles. I have since gotten it up to 18500. The car had all fluids replaced in engine and trans, had all new seals put on rear end. Car had synthetic oil change at 16k miles with filter, also changed out gas filter which I found to be the original (heh), changed out Tires and rims (which were original). Car was perfect, interior flawless, T-Tops - non leaking version hah Lastly, I had msd ignition wires and new bosch iridium plugs put in a week prior to LT install and tune.

Moving forward, recently installed SLP lid, K&N filter, and then went to a guy who works on tons of LS1's and even has his own track LS1, install BBK LT headers with the included Catless-Ypipe and then Tune it from his auto garage. Now, PRIOR to this install. I always record my MPG by doing full tank fill ups and running it to about 200 miles or 300 depending on city or highway and divide by number of gallons added next fill up. Install was done, and I had to drive from Joplin MO to Springfield for hospital work. So for 2 days straight I went to and from Joplin MO to Springfield MO, the drive is exactly 1 hr 15 min. start to stop. I went 70-75mph on cruise control, no gunning it (I am attempting to make sure the tune went ok and to gauge my new MPG). Prior to the install and tune, THIS CAR for 4000 miles. had a nearly consistent 17 mpg city, 23-24 highway (which was in TAMPA FL, in the SUMMER) After the install and tune, the car got, on 2 complete fill ups, I got 17 mpg all highway only miles in mild winter with virtually 0 traffic. So I was upset and confused, took it back and had him relook at the car, tweaked some minor stuff for me, retuned some things but mostly it was all good. the files actually posted in the tuning section of this forum if you would like to see them to help. So I kept it for another week after these trips and only did city driving. Posted a 13mpg avg the very next full tank.

To recap, thats 24 highway, 17 city. To 17 highway/13 city

Needless to say I brought it back to him did a few tweeks (mostly to shift points on the tranny) but A/F was all gravy and everything looked good (also looked good to people in the tuning section of this site). So, after getting it back, I have now taken the car only to and from work. This is a 5 mile drive with light to avg traffic for a small town of Joplin for the last week and a half (nothing like my city driving in Tampa FL). After I filled it up today it was 136 miles on 11.9 gallons!! Thats like 10-11 mpg city! This is NO a/c, no gunning it, no fun in it whatsoever I simply turn on and go to work and back. I drove this car like a madman when I first bought it, enjoying the car, gunning it every light, going 90 on the highway etc, still got 17/24. I haven't driven any car, let alone this camaro or my old one like I have been since the install. (normal/totally babying it/ no fun whatsoever) It literally goes to work and comes home.

With all that said, can someone, anyone, PLEASE help us figure out what might be up with my baby?! We are certain it is NOT the tune but we are just are stumped at this point. I will buy you beer if you get it back to 17/24....seriously, maybe even come give you a big hug for Christmas!!!

P.S. MPG is calc using Fuelly. Every time, it was 17+/23 or 24+ like clockwork. My driving habits haven't changed, well that isn't correct. I went from driving it like a Camaro, to driving like an old man with the joy literally stolen from my ride.

Mbysoon?

Try driving it hard again, should give you a moderate MPG increase... In all seriousness I hope you get it figured out I know how it feels to have your baby not acting right. Could it be the fuel filter is leaking or something along those lines? I see that it was recently replaced, maybe somebody oopsed it.

Sean Goodwin

Thanks man. Actually, it was replaced much closer to when I first got the car but a bit after the initial oil change. The newest piece to the puzzle aside from the LT and OR-+ tune is the plugs and wires. They were put in the week before. Haven't gotten them checked out yet, that is wed. Aside from a bad O2 sensor (which wasn't bad during tuning) or leak with the clamps or a plug/wire issue, I am just stuck. That is why I am putting it up on here for all to throw the ideas our way. I know Ben can figure any of it out if he has time in his shop and I find tons of money for diagnostic shop time, I mean after his build this should be cake

also I WOULD LOVE to drive her hard, except I make 18k a year cause I am in an internship right now and 10mpg city is already bad enough, I don't want to see it at 4, which at this point, driving it hard would probably do to her considering that 10mpg was with it driven like a prius

It could always be the fuel lines. I made a joke earlier, I think god is either siphoning the gas out of my car at night or maybe I just have leaking fuel lines. But considering the condition of the car in general, I doubt it. The car runs super strong, the tune feels great, just gas is magically evaporating from my tank.

gagliano7

Do you have a way to check your fuel trims? There could be some exhaust leaks that would tell the pcm you are running lean so it adds fuel. You could also have a problem with your 02 sensors acting lazy since they are farther down in the exhaust.

SlasherVRGR

iTrader: (1)

Do you have a way to see how the o2s are acting? It's quite possible they need replaced. I know every time I've done coated headers, quite soon after the o2s shat out..

Sean Goodwin

the guy who installed and did the tune has that capability. Wed he is getting the car back. We decided to try with new O2 sensors. In regards to fuel trim, when he had it last week he said they are on point and he had Widebanded it as well but we are going to check that again this week. The tuning file is under the tune section for called "poor mileage after longtubes and tune." We know that the tune is not the problem. Its been checked 3 times. We think there is a mechanical issue. Just not sure what might cause such a massive mpg drop

joecar

New *GM* O2 sensors.

Replace K&N filter with WIx paper filter (see next point).

Clean MAF using non-residue cleaner (CRC MAF cleaner).

Drive it like you almost stole it.

scout2000

Certainly, it could be a fuel line issue as was mentioned earlier, and that is something much easier do diagnose there with the car vs over the Internet.

That said, in addition to your new tune, you mention a small laundry list of mods and parts that have been added to your ride, all in a relatively short time.

Without any "smoking guns" here, or any other obvious leads, myself personally, I would go back and explore each one of those newly added/modified items one on one.

Good luck and keep us posted.

Deeohgie69

iTrader: (3)

Yeah I would try this^^^

The oils from the k&n, if over oiled at all can gunk up the maf could cause part of that. I believe the side of the cleaner says something like 7-10hp in a can and if dirty, it's true. Had that problem with my 89 trans am and after I cleaned it I felt the difference, no lie. Pulled the k&n out and threw a acdelco back in it.May not be the problem, but it's well worth the shot.

I also had both of my 02 sensors go out within one week of each other after my cam and header install. My car only had 15,9xx miles on it at the time, I put the ones in that I couldn't use on the install and fixed it. Also, have you checked the gap of your plugs? Does it smell rich when it's idling or just like normal exhaust?

jimmyblue

iTrader: (11)

O2 sensors are never happy with long tubes and your
idle / slow street driving will suffer. This is pretty much
universal. You can get some of it back but probably
this is going to take more time than the shop wants to
throw, or you want to pay for.

It's not that the sensors go bad, you ruined their
environment is all. The best thing may be an open
loop tune, if your weather / gas / state-of-tune is
consistent enough (or the modifiers are tweaked
to make adaptation to environment, better - but
again, see time / $).