Hello everyone.
My brother has an '04 Impala SS 3800 S/C.
He has a few mods done to it: 3" downpipe, Hi-flo cat, u-bend delete, 3.2" pulley, ZZP PCM, ZZP "power-log" front manifold, 2-step colder plugs (ngk something or others, tr6 maybe?), WAI.
The car isnt beat to hell really, but its not babied either, driven like anyone with a heavy foot would.
The other night we were at jewel about 1 mile from home, just on the throttle a little bit and it started shuddering. The car makes no funny noises, nothing mechanical banging around and idles fine.
The car shows almost no knock (when its cold, and youre not mashing it, which was the case for this trip).
when you step on the gas it sounds like the car is missing, it still has a bunch of power, but its not 100% when this is happening.
there is no code, no CEL.
The plugs look good, (gapped at .052 i believe, whatever number was recommended for them, maybe .052 isnt the number im thinking of).
The only thing I can think of is that a coilpack is losing it or something, the car registers no knock when this "missing" is happening, part or a fast full throttle.
Im stumped, any ideas before we start throwing on parts?
thanks for any help
Matt Linke wrote:Hello everyone.
My brother has an '04 Impala SS 3800 S/C.
He has a few mods done to it: 3" downpipe, Hi-flo cat, u-bend delete, 3.2" pulley, ZZP PCM, ZZP "power-log" front manifold, 2-step colder plugs (ngk something or others, tr6 maybe?), WAI.
The car isnt beat to hell really, but its not babied either, driven like anyone with a heavy foot would.
The other night we were at jewel about 1 mile from home, just on the throttle a little bit and it started shuddering. The car makes no funny noises, nothing mechanical banging around and idles fine.
The car shows almost no knock (when its cold, and youre not mashing it, which was the case for this trip).
when you step on the gas it sounds like the car is missing, it still has a bunch of power, but its not 100% when this is happening.
there is no code, no CEL.
The plugs look good, (gapped at .052 i believe, whatever number was recommended for them, maybe .052 isnt the number im thinking of).
The only thing I can think of is that a coilpack is losing it or something, the car registers no knock when this "missing" is happening, part or a fast full throttle.
Im stumped, any ideas before we start throwing on parts?
thanks for any help
impalas came supercharged ?
This one, its the '04 SS Indy500. I dont know what other year/level impalas had this motor, but this one does.
yeah, i believe '03 and up impala and monte carlos ss's have the L67 in them (3800sc)
i'd say your brother screwed his car up. 3.2 is a pretty small pulley for just 3"dp, powerlog, u-bend delete, generic tune pcm, and plugs... and i wont scold about how bad a WAI is on a unintercooled supercharged engine. you want as cold an air charge going into the engine as possible, and the 120*+ temperatures coming from under the hood definetly dont help with the knock he was probably seeing anyway.
just for reference, i've got an XP cam, TOG headers, custom PRJ tune, 3" catback, speedbuild fenderwell intake, and a 3.3" pulley. now, i could probably go 3.2 or 3.1. but i said probably, not definitely.
Quote:
The car shows almost no knock (when its cold, and youre not mashing it, which was the case for this trip).
ok, so this confuses me a little. it showed ALMOST no knock.... under NORMAL driving conditions???? how much is almost? and are we talking about non 100% throttle knock? a little knock is really too much knock for these engines. they're picky little buggers. 1 to 2 degrees at WOT can damage a piston and cause it to pop later down the road. now, if you're getting KR in normal driving, it could be false... but it sounds to me like his wasnt false. and if he flogs on the car often, it's all the worse. the plug being fine confuses me. i'd say he's got a chipped piston. but usually that would smash the plug. maybe he's just one of the rare ones where it goes straight out the exhaust and misses smashing the plug. he's gonna need to look into the cylinder using a boar scope. he probably wont like what he sees. and then he'll need to look for a junkyard engine. i'd tell him not to bother with rebuilding. it'll cost more, and probably not last as long. also, tell him to go to clubgp.com. anything else, just ask.
Andy
it's not how fast you go, it's how you get there that counts.
ZZP XP cam, 1.6 rockers, 105# springs, speedbuilt FWI, 3.3" modular pulley, TOG headers,
3" exhaust, flomatched injectors
'97 GTP 14.06@100.6mph pre cam w/ 3.5" pulley, I/E
He was going by what ZZP was telling him as far as the performance mods he's got. I tell him what I think and he doesn't listen to me for anything.
A friend of mine has the same setup with a stock pcm and doesnt have this problem. He takes the car to the track and everything, and doesnt monitor it at all.
My brothers car under WOT in the cold weather showed 0-2KR. Back when he had a 3.4" pulley without the tune he pulled nearly 10 KR at WOT, and then immediately purchased the ZZP PCM. I dont know how its tuned or what he had them do to it, if that was even an option.
There was no knock when driving normal, not WOT.
Sorry i wasnt too clear in the first post.
He was driving it last nite and said the symptoms went away, which is odd to me. Is that something that is possible with a chipped piston?
thanks for the help!
well if you said its "missing" as in misfiring, start looking into it. You said the plugs were fine I'd start with looking at the coil pack/wires. Take a spray bottle with some water and spray down the coils and wires while its running. if nohtign happens try brake torqueing it a little bit while its still wet. if it starts misfiring you will see and hear the spark coming out and gorunding out on somethign metal. Its a very simple quick test, thats what i would start with.
