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 Small engine vibration at idle

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jdbell2004
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PostSubject: Small engine vibration at idle   Tue Jul 29, 2008 11:38 am

1997 NA with 103K. I noticed when I got the car that the engine vibrates enough I can feel it while in the drivers seat. A friend of mine told me it seems like its missing a little. I don't feel it under load. Should I start by changing plugs? What brand and gap?

-Jon
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AA
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PostSubject: Re: Small engine vibration at idle   Tue Jul 29, 2008 12:37 pm

That sounds like a good start. Maybe replace the ignition wires, too. Any brand plug should work. Gap = .060"

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'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
KYB GR2 struts MaxAir shocks Addco sway bars UMI bushings GM STB Enkei 18" EV5s w/ Dunlop DZ101s F-body calipers
EBC bluestuff/Hawk HP plus SS lines Brembo slotted discs DHP tuned Aeroforce Hidden Hitch


'05 GTO 49k miles 0-60: 4.8s 16.9 avg MPG Nelson Ledges Lap: 1:26
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deekster_caddy
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PostSubject: Re: Small engine vibration at idle   Tue Jul 29, 2008 1:16 pm

My car used to 'spit' a little at idle. I had some bad injectors. Put 'new' (cleaned and flow tested) injectors in and idle cleared right up.

After, of course, everything else is in proper tune.
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AA
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PostSubject: Re: Small engine vibration at idle   Tue Jul 29, 2008 1:18 pm

Maybe try some injector cleaner before changing them out, but deekster is right - could be injectors acting up.

_________________
'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
KYB GR2 struts MaxAir shocks Addco sway bars UMI bushings GM STB Enkei 18" EV5s w/ Dunlop DZ101s F-body calipers
EBC bluestuff/Hawk HP plus SS lines Brembo slotted discs DHP tuned Aeroforce Hidden Hitch


'05 GTO 49k miles 0-60: 4.8s 16.9 avg MPG Nelson Ledges Lap: 1:26
Because fun
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Mr.Riviera
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PostSubject: Re: Small engine vibration at idle   Tue Jul 29, 2008 6:35 pm

cleaning the MAF and changing the fuel filter are some more things you may want to try after the plugs and wires.

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PostSubject: Re: Small engine vibration at idle   Tue Jul 29, 2008 6:35 pm

Seafoam FTW
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jdbell2004
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PostSubject: Re: Small engine vibration at idle   Sat Aug 02, 2008 2:47 pm

I checked the service records, the plugs and wires were just changed 20K miles ago. I just filled up with premium and things seem to be running better. I suppose I could check, but what octane rating gasoline should I use? How do these cars run on gas with ethanol? Regular gasoline here has ethanol in it.
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jdbell2004
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PostSubject: Re: Small engine vibration at idle   Sat Aug 02, 2008 2:48 pm

manofmany wrote:
Seafoam FTW

My gas gage reads incorrectly and I heard it's because the float starts to rust. If I run seafoam, will it break this rust up and clog the injectors or filter?
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PostSubject: Re: Small engine vibration at idle   Sat Aug 02, 2008 3:02 pm

Although it may have seemed to help, using premium shouldn't make any difference with the N/A 3800. Shell's "V-Power" is supposed to have extra cleaning agents in their premium that could make a difference, but otherwise I wouldn't waste the money. Use 87 octane.

Regular gas only has a small % of ethanol. Using E85 will not result in less power output, and it will clean out your tank and fuel lines, which could result in clogged filter or other problems. I wouldn't use straight ethanol in your car.

I think you'd have to out a lot of seafoam in the tank to break the rust up that much, but changing the filter is rather easy, so why not?

_________________
'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
KYB GR2 struts MaxAir shocks Addco sway bars UMI bushings GM STB Enkei 18" EV5s w/ Dunlop DZ101s F-body calipers
EBC bluestuff/Hawk HP plus SS lines Brembo slotted discs DHP tuned Aeroforce Hidden Hitch


'05 GTO 49k miles 0-60: 4.8s 16.9 avg MPG Nelson Ledges Lap: 1:26
Because fun
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jdbell2004
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PostSubject: Re: Small engine vibration at idle   Sat Aug 02, 2008 11:55 pm

I'm going to take a video from inside the car to show you how the rpm's bounce a little. I'll shift through the gears as well.
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jdbell2004
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PostSubject: Re: Small engine vibration at idle   Sun Aug 03, 2008 2:51 am



Is this normal? The car was already warm. It seems like it idles high. I shifted from park to reverse to drive then back to park. It wasn't really idling rough during the video. It seems to be intermittent.
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96RIVMANN
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PostSubject: Re: Small engine vibration at idle   Sun Aug 03, 2008 9:49 am

I had the same problem on my '96 so I decided to pull the throttle body off and clean the MAF and up inside the super charger.

http://rivperformance.editboard.com/series-i-engine-transmission-f13/mass-air-flow-t2149.htm
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