Thread: Vibration and shudder with lots of boost

I have a recently acquired 99 GTP. Supercharger sounds fine at idle - not rattles -though it does seem to get quieter at 30+. It's been fine driving at low speed and highway speeds. But on a certain trip with some hills at highway speeds when it downshifts to climb a hill and the boost jumps to 80-100% the car vibrates and there's a unhealthy rattle/vibration that sounds like it's coming from the motor. That's really the only time I've seen boost that high so I can't say if it would happen under other driving conditions.

I did change the supercharger oil, was low and pretty dark. Check a few plugs and looked ok. Scanner shows no codes. 206K on motor, 70K on rebuilt transmission. Any thoughts, hopefully it's not destroying itself

Is it only when accelerating? If under a hard load or wot it could be something loose in the steering, suspension, or CV axle. When I got my car I had what felt like what you are describing. Mine had bad hub's, lower ball joint's, outer tie rod's, and both CV axle's. I don't know what item in particular was causing mine but after I replaced all item's and aligned it the vibration is gone.

Check for somthing loose in the steering and try to shake the cv's from under the car and listen for clunking and feel for movement. Check to see if they have exploded grease all over.

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Originally Posted by ericspecullaas

Try the zzp coupler. I have a 99 as well and my snout was shot. Do you know if your snout was rebuilt or not? Also if you dont mind post a video up of said sound

I wondered about the coupler, it seems like when that's the issue it's sound like gravel banging around in their at idle? I listened to some videos and mine seems ok at idle. I don't think it has been rebuilt, have the last 100K worth of receipts. Can get a recording of it at idle, may be a bit before I can get it somewhere I recreate the vibration. Was going to the last time it happened but by the time I got my phone out I was already over the hill

I've stepped on it a bit passing people and it's fine, it doesn't really get too much boost though. When it's happened I'm just going normal highway speeds with cruise set and get to decent sized hill, it downshifts, boost shoots way up, and then all the noise starts. That's what made me initially think it may be a supercharger issue

It's had a fair amount of work done by the previous own, I'd compiled it from the receipts:

6/15/2012	198,057	Oil Change (inspection all passed) 5w30
3/20/2012	195,057	Replace FR Wheel bearing, real brake bad/rotors
2/17/2012	194,299	Alternator (battery 2 yr old)
7/15/2011	186,444	Traction Control C0035/C0036 Left Front Speed, sensor gooddamaged wire on left front wiring harness declined repair
7/5/2011	186,158	Exhaust leak, installed 5in pipe 54-8518
6/17/2011	182,788	New Radiator hose Replace front brake pads/rotors/RF Caliper Installed exhaust flex pipe/MAF sensor?
6/8/2011	181,731	Radiator (1890) Aftermarket, not perfect fit
4/27/2011	182,788	Replaced front tires
3/25/2011	181,346	Left outer tierod, rf lower ball joint, front sway bar, left rear trailing arm
4/13/2010	165,839	repaired radiator fan wiring
9/23/2009	158,764	Replace both belts 12588411/12574914
6/2/2009	154,043	Overheats: Replaced lower intake manifold gaskets/related/thermostat
6/21/2008	136,878	Recall/Left Valve cover gasket & wire retainer
3/16/2008	~136000	Tie Rod/Front Left Hub/Left CV Shaft/Fuel Filter/Exhaust Gasket
2/23/2007	130,845	New Transmission
11/9/2006	126,000	Replace both swaybar links
7/13/2006	-	Windshield

Originally Posted by osiris94ej

Is it only when accelerating? If under a hard load or wot it could be something loose in the steering, suspension, or CV axle. When I got my car I had what felt like what you are describing. Mine had bad hub's, lower ball joint's, outer tie rod's, and both CV axle's. I don't know what item in particular was causing mine but after I replaced all item's and aligned it the vibration is gone.

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Thanks, I'll check out the pull when it warming up a little in a few days, barely double digits today

I got a few video clips, at idle:

http://youtu.be/cbd9pkNAsGE

I actually noticed it got louder when it warmed up, though not really rattling, it's pretty loud at the air filter at start

I also noticed I could get the rattle at lower speeds just by really stepping on it, though to a lesser degree. Just been babying it a bit since there are a couple of things I'm worried about with the transmission. Can't really tell a whole lot from this clip, maybe it is suspension rattled since it does seem like it was a lot more pronounced at highway speeds

http://youtu.be/tSqkIFxyxuI

Yea that definitely doesn't seem like drivetrain like I thought at first.

Sounds like at least one cylinder down.

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Thanks for the replies. My service light is actually out and I'm about to replace the bulb (that and the ABS, was diagnosed a bad wire on VSS I saw so I found the break, ordered a new connector). Used a scan tool a while ago didn't didn't see any codes other than the bad bulbs I believe, have to check again now that I've been pushing it.

Think it may be the plugs? I'd just checked one or two and they looked fairly clean and had good gaps, but didn't check them all. They looked like gm iridium plugs, was guessing they were changed about about 100K by original owner, the second owner never changed them. I have a copy of alex peper's obd2 software I could have recording live on my laptop when it occurs

I just mentioned the ABS a side note as to why my check engine light has burned out because you mentioned the check engine light flashing as a sign, I didn't think it was related.

By tune up, you mean plugs and maybe wires? All of the other little things have pretty much been done, ie re-oiled air filter, changed fluids, etc

I believe I followed the instructions, running a bead down each pleat. Would it have thrown a code if the maf was bad?

I think the original owner put it in, I cleaned it because it was pretty dirty. My kit had a squeeze bottle for the oil.

So does the maf seem like a likely cause? Is there something I can check to see if it's the issue? If there's no code, a sensor value when reading obd-2 data?