LS14Winter

I recently picked up an 04 GTO 73k miles with cai, long tubes, true duals, custom ground comp cam, msd wires, 241 heads.

The previous owner didnt know much about the car, he had it 3 years and only put 3000 miles on it. The car runs really good, sounds amazing, but i think its missing 60-80whp based on my highly attuned butt dyno. To me it feels like a stock LS1 without the low end torque.

I just put new plugs in it, looks like it had AC delco iridiums, stock part number. I put in NGK TR5 and it certainly runs smoother. All the original plugs look a bit white to me -- im not sure if there is normal wear and tear or a lean condition.

Also on some wide open throttle pulls through say 2nd (after 5000 rpms) gear a service engine light comes on briefly. I think the car runs too good to be untuned, but at the same time i think its maybe running really rich down low and lean up high ? The power band is strange. Doesnt make much torque down low (doesnt spin the tires) but power starts to trail off after 5500...

Im going to setup an appointment for a dyno to see what it makes and more importantly the AFR... any other ideas welcome

link to pic: -- all eight plugs look the same

Blk98Vert

iTrader: (2)

Sounds like a tune or fuel issue to me, get it checked out asap

thompson

iTrader: (4)

Definitely get the tune checked out but why TR5? You need more like a TR55, something a little warmer than stock.

LS14Winter

I couldnt find TR55 in stock anywhere around me, didnt want to wait for shipping.

Video of the idle:

svede1212

iTrader: (3)

If the light is coming on even briefly at WOT don't go WOT. If it's a lean condition you risk punching a hole in #7. It sounds like the car's easy life is over.

LS14Winter

Ehh, i dont want you to get the wrong idea. I drive the car pretty gentle 98% of the time, never do any brake stands, donuts, etc. However, i do like to briskly merge on the highway every now and then. :-)

Its just this should be the fastest car I ever owned and it doesnt feel like it at all. My modded 2000 trans am would lay end less amounts of rubber on demand anywhere under 50mph if i punched it. that had wider / stickier tires to boot. ran best of 12.8@110 though still had some kinks to work out.

This GTO feels like a 13.9@101mph car to me and based on what ive read and know about the car it should be more like a 12.5@113mph car...

redtan

iTrader: (5)

At WOT, a flashing CEL means missfire...a flashing check engine oil message means low oil pressure.

Either way, I would not take the car WOT until you figure out what's wrong with it and fix it.

And don't take it by your butt dyno so much, as highly tuned as you think it is. Until you put it on a dyno or take it to the track your "guesses" mean squat.

LS14Winter

Yeah, since then ive been really careful with it. I am trying to setup an appointment with a local tuner asap. Ill post my results when they can get me in... Ill be surprised if it makes anywhere over 320whp in its current state though.

redtan

iTrader: (5)

Being careful is not taking it to a tuner to have him beat the **** out of it on the dyno...you're supposed to fix the issues before you go hard on it again. A tuner is not going to fix your missfire and low oil pressure by putting it on a dyno.

But alas, you seem to just want a new engine...

RsSean

iTrader: (27)

Put a set of tr6s in it, and have some one look at the tune file before further. You may have a dropping off coil under load, wire, or a tune out of whack

Izzy256

The first thing I would think if you are getting CELs is to have it scanned and see what codes it is throwing. You can start diagnosing issues from there. I agree, definately do not do any WOT or high RPM pulls until you get it figured out.

thehazz12

I'zm in agreement that tuning is not the best thing for you at all.