Grant B

I agree. These typically disapear at WOT (hard to see on a narrow-band O2), but of course they will still fubar your fuel trims.

I wish someone made a 90mm TB for the LS6 intake. Well, other than that $$$ TPiS oval intake/TB conversion.

Out of curiosity, why do you guys tune only on the dyno? You can easily run leaner during a short 4th gear dyno pull w/o knock than you can for an entire 1/4 mile run or a 1 mile top-end blast.

C5X2C

Mirek - My mechanic replaced the rear O2s that we were already using with new rear O2s.

Tony - Thanks for the suggestions. I will mention the A/F ratio to my mechanic as well as the o-rings. He did a smoke test on the intake and could find no leaks. He still thinks that it is a bad coil and wants to replace the remaining 5 coil pack (already replaced 3). I would think that incomplete burn means more fuel not more air, but what do I know. I kept the stock 78mm TB with the FAST intake.

FAST98 - Driver's side LTFT are always positive and adding fuel. Yes there are all sorts of misfires also.

I will be out of town and won't be able to get back to my mechanic until April 4. This doesn't leave much time before Thunderhill on April 15. It's got to come together.

Thanks for all the help and suggestions!

The Dragon

iTrader: (6)

Do you have your own diagnostic tool? How knowledgeable about tuning are you? I ask because I can offer assistance but I need to know you can understand my queries

chevydan

iTrader: (4)

C5x2 just replace the intake for the stock ls6 and see if the problem is gone if it is youknow what the problem is .

DaddySS

This sure sounds like an intake issue. I agree, put the LS6 intake on and see what you have.

MrDude_1

iTrader: (4)

its that or your header is leaking somewhere and thats messing with the O2s.......

Spellbound

I hope he is just R&Ring the coil packs from known good ones to see if they are bad. He has plenty to choose from in his shop.

Grant B

In my experience, if a cylinder is missfiring enough to make a wideband show lean, you will feel it. Although thats on a 6 cylinder motor, so I guess it would be less noticable on a V8.

A missfire causes a lean reading because there is a lot of O2. The sensor of course reads O2, so it reads lean.

Louis

iTrader: (7)

Where are you located? There is a solid 15-20 hp to be picked up in the nitty-gritty details that I can see right off the bat.

C5X2C

Louis, I'm in the Sacramento Area.

CHRISPY

sounds like a intake manifold leak to me. FAST intakes are known for this. check your PCV etc as well.

Numbers are pretty good considering everything. driveability will be WAY better when you get the leaks sorted out

ArcticFormula

Let's see your last dynograph. Numbers are very nice in my opinion, sorry to hear the car is running like crap.

Blktie8

iTrader: (1)

Sure sounds like an intake manifold leak

C5X2C

Was back at the shop today. I think he did some computer work as we started to replace the coils (computer hooked up to car). I didn't quite catch what he did. Replaced the remaining 6 coil packs and it ran much better I think at idle. It would throttle down well to a 900 rpm idle, not choke at 600 for a while and then catch up to 900. Most of the misfires have stopped except for #2. Tried a new plug and wire, no change. He did some kind of fuel injector signal test and initially #2 looked weak but then it didn't. Idling was not a problem but at 2500 #2 was registering may misfires. Still reading lean on that side. Mechanic asked to look at car again, to swap fuel injectors (I thought he did that already) and take a look at the lifters, perhaps #2 is sticking?

Perhaps Friday

C5X2C

Friday has now turned into Monday or Tuesday. I have now postponned my TrackMasters time at Thunderhill next Friday. Bummer, I was so looking forward to stretching it out a bit. More track time in May.

C5X2C

I am dropping it off again today so that it can be fixed. What else could it be? Everything has been replaced! - (All coil packs, O2s, plugs, wires, intake manifold and gaskets, injectors, heads). It appears to be a leak somewhere. I think that I will leave it at the shop until this lean condition on one side is corrected for good. I started it up and it would barely idle cold and didn't drive well. Soooo very frustrating!

z-ya

iTrader: (1)

It appears you have replaced everything but the mechanic,maybe thats the issue.

pdd

iTrader: (3)

good luck with it. i feel your pain the numbers arnt that bad. i made 435 rwhp with afr 205's and the fast 90 setup last year with a bigger cam than you. hopefully this year ill make lots more

WS6snake-eater

I agree

jub jub

Here's an old trick. Take a piece of 3/16" vacuum hose about 3' long and use it like a stethoscope. Probe around the injector bores and where the intake mates with the heads. If there is a leak, you'll be able to here it easily! Another thing you can do is to remove the lid, start the engine and cup your hand lightly over the MAF. If the engine RPM picks up, you have a vacumm leak, if the engine wants to stall then you have another problem. All the symptoms you've described make it sound vacuum related.

Good luck!