Thread: Flashing SES @ 120MPH almost every time...

Okay here's the deal i have a 2006 Pontiac Grand Prix GT with L32 and 92,000...so, the car runs and drives like a dream, other than annoying suspension creaky bushings...but, i've noticed rather horrifyingly that if i do a high speed pull, by the time i hit 120 it hauls getting there, and at that point it seems like it hits a brick wall while the DIC still shows "full boost", the ses begins to flash, and i stop and glowing front and rear exhaust manifolds, and while the Cat is not glowing the piping directly before and after are glowing as well. i did capture a code which turned out to be a misfire in cylinder 1, but i don't always get that..... Do we think its the cat? if so i'll definitely be doing a downpipe w/out cat blah blah......I don't have a scan gauge handy and am just trying to detail it for you guys...this happens whether i run Stock Platinum AC Delco or Autolite 605 (one-heat range colder) Coppers... This car now has an Overkill tune which i adore, but the problem still persists...Under wide open throttle, like i said its fine until almost 120mph...

ehhh, i'm trying to only diagnose problem that didn't always occur, you see i used to be able to peg the 140 ...don't worry its on a closed (no traffic) road...by an airport...where no ones looking

Oh my aren't we a bunch of help.......so all of you guys that modify your cars for more power only do 100mph? these cars can't perform well out of the box past these speeds? i'm just looking for answers...the car hasn't always done this and used to perform flawlessly in stock form, i'm sure i have high egt's thus the glowing....please be helpful and not just make ridiculous comments...mine came with platinums...and don't give me the someone will get hurt...it's my car, its my body, leave that subject alone...

i understand the safety but i don't have a track for 70 miles and it's only 1/8 mile , thats why i do it on good roads in the country...minus the deer factor, but it is just my daily driver and am not sure whether i want to spend the money for headers, or just do a downpipe and cat delete... scottydogs, i understand about the platinum plugs thats why i went to copper and one heat range colder to 605's...i understand completely the plug factor in these cars. and answers like from icemann...thats what i'm looking for...does the average 3800/s/c stock pull alot of timing past 100....and with perhaps a clogged cat might be amplifying the issue...and yeah i hope i haven't damaged the motor either...not to worry it blew the coolant elbows driving down the highway and didn't know it till the coolant light came on in 95 degree weather at a stop light and pegged before i could shut her off xD...replaced with Aluminum lol

I used to have a thread bookmarked with a huge write up about mods and they said to either stick with stock heat range, or you could go one down safely to try and kill some KR...is that information correct? While i'm still trying to kill myself (which most likely i'll do on the street bike anyways), i know there are writeups but if i go with a cheaper set of Pacesetters/zzp downpipe, probably go with a retune from Overkill, what other recommendations would you make? 605's, 606's? eventually i'd like to drop to a 3.6" but...one thing at a time right...don't need the Heaton blower, making more heat at the moment...also....forgot to mention, think i should get rid of the Duralast and go back to AC Delco plug wires? and to GMR...the 605's i have are brand new and i've already pulled it and looks almost brand new, unless theres something i'm supposed to be looking for...doesn't look like it blew it up in the combustion chamber anywhere but maybe i'm not looking for the right thing xD...and to the chipped piston...what i don't see nor know, won't hurt me, till down the road...and also no supporting mods...i had a K&N intake on it, but went back to stock for the time being...

Originally Posted by GMR Badass

The heat ranges of spark plugs is a rating of how quickly they can dissipate heat. In the grand scheme of things they do very little in terms of reducing KR.

Blasting down a back road at 120 (stupid but we've all done it at one point or another) in a very close to stock car puts a ton of load on the engine and is going to cause a lot of heat. This particular motor doesn't do so well with that much heat, keep it up without supporting mods and expect a chipped piston.

If plugs are good I'd be looking to see if your cat is on it's way out. A restriction in the exhaust like a failing cat with cause the car to fall on it's face at those speeds. Stock replacement wires is what I run.....to me doesn't matter what brand as long as they don't arc. If you're seeing misfire on cyl one try to diagnose why that cyl is giving you trouble. Inspect that plug, wire, and coil......swap coil and see if misfire changed to a different cylinder.

Long story short...yes the car can go that fast.....but without proper supporting mods you're flirting with a ticking time bomb.

Thank you for the advice, and a few words perhaps if i want to spend around $800-$1000 for best mods possible regardless if the cat is on its way out or not? I'm thinking Header/Tune Route...Seem wise enough? Also, i used to have an arcing issue when i first bought the car at 67,000 miles and i removed the Boot Heat Shields....think that's safe after a header install? and last but not least at the moment....I can't seem to bring myself to actually go to a 180 Thermostat...To me if it was designed for 195 as optimal....is that bull? or do you guys have facts to back it up...i see almost unanimously to go to 180, but i'm not sure i'm willing to..

Originally Posted by GMR Badass

3" downpipe, Full size IC kit.......Intercoolers are by far the biggest help in cutting down KR.

Can i really do 3" downpipe & Full IC for under a 1,000?