Thread: Need help....sputtering bad

Well I searched the forums for this problem first but have found no difinitive answer so hopefully someone can help......1999 gtp, borla cat back, modded dp, 3.4, custom air intake, 140k. Checked the plugs and they were v-grooves gapped at .050 and badly worn. Decided to change plugs and wires....replaced with autolite 606 and msd 8.8s. Ran great for about a week then started sputtering bad under load....as soon as boost gets near 5psi or over 1/3 throttle. Pulled a 301 code so decided to change cyl1 plug again just in case....changed plug and wire again. Still same prob so replaced coil w oem style.....still same issue.......sumone please help.....i love this car but my mechanic dosn't even know where to go now

Check coils? Try swap one to the other and see if the misfire changes cylinders.

Per the "Safely Modding your 3800 powered car" thread...

you want to keep a hot spark. NGKTR55/AL104's for your 3.4" Setup, TR6's are a tad cooler

AC Delco Factory Replacements: Stock
Autolite 606: Stock
Autolite 605: 1 Heat Range Cooler
NGK TR55: 1 Heat Range Cooler
Autolite 104: 2 Heat Ranges Cooler
NGK TR6: 2 Heat Ranges Cooler
Autolite 103: 3 Heat Rangles Cooler

6) Exhaust - Here is where a lot of misconception tends to occur. Many people think that when someone says exhaust work that they can run 3” straight pipe from the cat back and drop to a 3.4” pulley and think that they have done enough exhaust work. Hardly. The cat back is the least of your worries as is flows good enough and has been dyno tested to not show signs of flow issues until 350+WHP, which is around 400hp at the crank.

Other than your Borla catback and "modded dp", what have you done to actually increase the flow (ie- are you running stock exhaust manifolds?). Hopefully this is just a bad coil or injector. Is it misfiring on this cylinder only, or multiple ones?

Coils were swapped....always stayed cyl1 misfire. Running stock manifolds and stock cat..... Plugd were not smashed when replaced, the car actually ran very well with the worn plugs and old wires, never had an issue until 5 days after plugd and wires were changed

Little extra info.......
Gapped new 606s at .060
Car runs very consistent 180 degrees
Vaccuum is 20in at idle in park, 18 in at idle in gear

And again....car ran perfect on old plugd and wires but the were visually worn and old that's y I replaced them

Ok so I read the 'safely mod' section....it says I should use tr55 or 104......im a lil confused tho, a cooler plug =hotter spark? Just tryin to find a definite answer before I change plugs again.....i read multiple posts but can't find an exact answer

I kinda don't understand the plug thing.....cooler plug equals hotter spark??? According to the thread I should b running tr55 or 104 both of which are cooler plugs, but I want hotter spark??? Confused.....and the copper, platinum, iridium thing is confusing too.....i put 606 double platinums in and I think that's where my problem lies

I don't have anything to scan kr with....i take it to my buddy to check ses light. I'm going to try running the al104 plugs like the mods thread says and see if that helps.....they are only a few bucks ea

I kinda dont know wat else to do....car ran great on the v-grooves I took out but the were worn to the point that the groove was almost gone......several people on this board say not to use platinums.....maybe switch to copper 606s?? Or should I swap out the icm

I bought the car with the mods it has on it.....put 20k on it without one bit of trouble....idle is smooth....acceleration with no heavy load is smooth......no knocks or pings ..... Only happens when under heavy load and only happened about 100 miles after changing plugs and

Cold or hot....not intermittent....constant problem thru any and all variables