As you can tell by the screen name, I'm an LS1 guy, but broke down, and bought an LT1 recently, a 93 TA M6.
Under part or WOT, it's breaking up from 3-4k, and will continue to do so until about 5k, but mostly 3-4 k. Even in neutral it will break up/stutter there?

Just some background on the car:
93 non-vented Opti w/ about 12-15k (who knows, 3.73s, not correction to the speedo/odo LOL)
MSD 6al w/2step
Hooker LTs, Mufflex Y and 4" single
Electric Water Pump
255 fuel pump
58mm BBK TB
Moroso CAI
LT4 Hot Cam
local LT1 tuner's tune (have a PCMforless tune also, which made about 20 more to the wheels, but less driveability)
It's seen some N20 duty as well, has run 13.1@109 on BAD tires, 12.1@118 on spray (same tires) 312/330 (+20 for PCMFL tune) and 445/545 on juice

Anyway, any ideas on the breaking up? I'm thinking at least plugs/wires, and opti cap/rotor. But looking around there may be other factors?

Any plug suggestion? Not sure if I'll continue the spray or not.
Probably going with the MSD cap/rotor also

 

A good shop with a highend scanner get print out your codes which many in here can help you with. My opti issues were @high rpm, replaced it and was fine, then 02 sensors went bad starting on the drivers bank, then my stock gm coil went out, on a multitester it should have 8000 ohms, but was putting out 6500, fixed that problem, with a new MSD Blaster coil. Sure some more will post to help ya.

Off topic sounds like you got a good car with the mods listed.

 

The odd part is no SES light?
I'd just like to trace it down. I know what the car can do, it's got a decent local reputation, but I want to see it for myself. I've got a full bottle, and can't fire it off! LOL
Thanks for the comment though, it pulls pretty well, even in current form, and sounds like a top fuel car My neighbors hate me, but now in comparison, my LS1 and Flowmastered Suburban sound tame

 

If you think it's an ignition problem, dig out your inductive timing light and see if the miss shows up in the flash pattern on each cylinder. Since you have LT's, you could possibly find the bad cylinder with an IR thermometer.

If I were you i'de pull the plugs and do a leak down test. Since it had N2O in it when you bought it, no telling if it was used properly or not. Could be a bad piston.

 

ok, this morning, seemed like a fuel problem, bucking and going lean (have 2 A/F meters, NOT Wideband though) like a clogged fuel filter.
When it would run straight, it owuld run like a scalded cat, right up to redline, or sometimes break up at 5k.
Ran SeaFoam top end in it, change the fuel filter. Same crap! Ran fine for the first few minutes, then bucking and surging.
Now tonight, bucking surging, breaking up. Then ran fine just cruising. WTF?!?!
I'm about ready to sell it already. I know LT1 had their quirks, and the Opti issues were what always prevented me from getting one. Now I remember why!

 

How do I change the PCM chip/board whatever it is? I'm thinking of trying the other prgram, and seeing if it runs the same. I'ms ure, with my luck, it's the Opti. What goes bad in the whole opti, as opposed to the cap/rotor on them?

 

ran great this morning for like 15 minutes, then started acting up again, breaking up badly, still seeming like no fuel?
Oh well, we'll know more tomorrow, when I change the plugs/wires. Previous owner replaced entire Opti less than 20k ago, sooo?!?!

 

Check the plug wires.On my 97 when it was a opti it missed up in the high rpm's.When it was the plugs it would miss all throw the rpm's.It would run good at 1st then got hot and started actin up.

 

plugs and wires being changed tomorrow. Any thoughts on the O2s being bad. I have dual AF meters, and one reads REAL lean and erratic, but you can't stand behind the car for more than 10 seconds without your eyes watering, it's so rich?

 

I would take a look at your EGR if it is runing good for 15 minutes,then breaks up after the car gets hot. I had the same thing happen to me on my 97 and it was the EGR:

 

My car ran pretty good with jus one 02 being hooked up no missing

 

How do I check it out? If that's the cultprit, is there any way to get rid of it?

 

oops, EGR already removed and tuned out of the car.

 

Try the easy stuff first. Iwould do plugs and wires first and then if that didnt fix it, I would then replace the opti which isnt as bad as people think. Good luck. BTW, if you dont want to replace it, I will.

 

my Lt1 hawk did the same thing. worked fine then about 3-5K it would break up. ended up being the rotor was coming apart inside the opti. me and a good buddy (ase tech) did opti, wires,plugs, waterpump, fuel filter, Thermostat in about 4 hours or so.