Vibration at very low throttle

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H

Howard

Lifer
Oct 14, 1999
47,982
10
81
I feel a vibration in the steering wheel and gas pedal when I move the throttle just a bit off 0%, almost as if I was driving on rumble strips (not that bad, though), except the noise and vibration is not coming from the tires... Stepping harder on the throttle gets rid of the noise and vibration, and there's nothing out of the ordinary at 0 throttle.

2005 2.8L CTS with stick shift, 60k miles
 
H

Howard

Lifer
Oct 14, 1999
47,982
10
81
twinrider1 said:
Does it idle smoothly? Sounds like it might be a miss. Check plugs, wires.
Click to expand...
Yes, it generally idles smoothly. About a month ago I had a cold startup with a lot of vibration, but it stopped shortly thereafter (less than 10 seconds, I think) and I haven't experienced it since.
 
amdhunter

amdhunter

Lifer
May 19, 2003
23,332
249
106
Howard said:
I feel a vibration in the steering wheel and gas pedal when I move the throttle just a bit off 0%, almost as if I was driving on rumble strips (not that bad, though), except the noise and vibration is not coming from the tires... Stepping harder on the throttle gets rid of the noise and vibration, and there's nothing out of the ordinary at 0 throttle.

2005 2.8L CTS with stick shift, 60k miles
Click to expand...

Edit: Misread the post.

Does it only happen in 1st - or R? What happens if you try to take off in 2nd? Do you feel anything on the clutch pedal?
 
H

Howard

Lifer
Oct 14, 1999
47,982
10
81
Happens in all gears, I think.

Clutch feels fine... but I don't really use the clutch in situations where I need to apply very little throttle; coasting, mostly.
 
amdhunter

amdhunter

Lifer
May 19, 2003
23,332
249
106
Howard said:
Happens in all gears, I think.

Clutch feels fine... but I don't really use the clutch in situations where I need to apply very little throttle; coasting, mostly.
Click to expand...

Ah. Maybe fuel pump is clogging? Injectors? (I am dumb when it comes to cars...so it's a guess.)
 
AMCRambler

AMCRambler

Diamond Member
Jan 23, 2001
7,714
31
91
I was going to say injectors too. Sounds like the engine might be stumbling a bit. I'd say fill it with 93 and take it for a nice long ride on the highway so it gets heated up good. Then see how it is next time you start it up from cold.
 
H

Howard

Lifer
Oct 14, 1999
47,982
10
81
It's not a cold startup problem, it's a low throttle problem. Happens warm or cold.
 
LTC8K6

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
126
Sounds like it's a specific RPM problem.

Trans mount? Driveshaft?

You can check for driveshaft and U-Joint play.
 
LTC8K6

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
126
Well, I wouldn't call 3K in gear "low throttle". :biggrin:

Maybe it is indeed a tire?
 
H

Howard

Lifer
Oct 14, 1999
47,982
10
81
LTC8K6 said:
Well, I wouldn't call 3K in gear "low throttle". :biggrin:

Maybe it is indeed a tire?
Click to expand...
It's low throttle when you're maintaining speed and not accelerating. It's not a tire because it happens right from a stop.
 
amdhunter

amdhunter

Lifer
May 19, 2003
23,332
249
106
I am still gonna guess it's the clutch going out.

It's probably slipping when you keep the car coasting and gripping better when under heavier load. Maybe its a clutch spring or something.

Do a 5th gear pull from a decently low speed and see what happens.
 
H

Howard

Lifer
Oct 14, 1999
47,982
10
81
It's now getting worse, and stepping on the throttle doesn't really make it go away - there's a noise when accelerating that's not just the induction noise that's supposed to be there...

candidates so far:

clutch
fuel pump
fuel injector(s)
motor mount
transmission mount
driveshaft coupling(s)
coilpack
 
Bignate603

Bignate603

Lifer
Sep 5, 2000
13,897
1
0
LTC8K6 said:
Sounds like it's a specific RPM problem.

Trans mount? Driveshaft?

You can check for driveshaft and U-Joint play.
Click to expand...

If it's driveline vibe after the transmission it should vary with the speed of the car rather than the speed of the engine.
 
H

Howard

Lifer
Oct 14, 1999
47,982
10
81
It does seem as though the noise is proportional to car speed... cruising on the highway, I'm generally around 3k RPM whereas I generally shift at 3k on the road too, and I don't get nearly the same amount of harshness. While cruising, it feels like the wind noise is almost being drowned out.

EDIT: I've also confirmed it's not the tires as I switched to my winter setup, which uses different tires on different wheels.
 
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