Whole car shakes at idle, need help

blackout51

Original poster
Member
Oct 18, 2012
157
Ok so I replaced my bad stock motor mounts with dea ones back in August, today I finally installed a pair of brand new gm ones, this solved my high frequency vibration but increased the subtle shaking I have had all along that now is ridiculous. I can watch my whole motor bounce and once I figure out how to upload videos who'll show what I mean. All bolts are tightened to spec on the motor mounts. Also I took off the belt to see if it was engine or pulley related, the engine still shook with the belt off. I have replaced all of the plugs last week, all the coils look good, I just don't know what is causing this shake. I do hear a weird noise down on the drivers side of the motor, it's like a cross between a sucking noise and an electrical buzz, I don't think it's a vacuum leak but I really have no idea, idle rpm stays steady at 600. Also if i push the gas and the rpms go any amount above 600 the shaking goes away and it runs and drives smooth, any ideas?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Did you use Delco 41-103 plugs? Check for vacuum leak? Tighten the intake manifold bolts? Check vacuum hoses?
 

blackout51

Original poster
Member
Oct 18, 2012
157
the roadie said:
Did you use Delco 41-103 plugs? Check for vacuum leak? Tighten the intake manifold bolts? Check vacuum hoses?

Yes I used those plugs, all the hoses look good, I'm about to go out and check the intake manifold bolts now
 

blackout51

Original poster
Member
Oct 18, 2012
157
Ok I tightened all of the intake bolts and swapped the cracked looking cover for the vacuum port (on the manifold under resonator) with a new one that looks good. The idle calmed down but it's still slightly there, think there's still another leak somewhere?


One other side note, I pulled up on the belt and lifted it about 2" above normal, could the tensioner be bad? That just seems awfully loose to me to be able to pull the belt up so far like that
 

CaptainXL

Member
Dec 4, 2011
2,445
blackout51 said:
Ok I tightened all of the intake bolts and swapped the cracked looking cover for the vacuum port (on the manifold under resonator) with a new one that looks good. The idle calmed down but it's still slightly there, think there's still another leak somewhere?

Ok, were any loose at all?? Idle rpm's are not an accurate indication of a leaking manifold. The PCM makes many adjustments to the throttle based on a number of factors. Most are not under your control. Your just shooting in the dark here. A vacuum gauge would be of great help in this case.

The bolts should really be torqued and then test for leaks using propane near the gasket sealing areas. If there is a detectable downward change in rpm or the engine dies then you still have a leak and may need new gaskets. The intake manifold has a particular torque sequence as well.

blackout51 said:
One other side note, I pulled up on the belt and lifted it about 2" above normal, could the tensioner be bad? That just seems awfully loose to me to be able to pull the belt up so far like that

It shouldn't be easy at all to pull the belt up. Sounds like you need a new tensioner. I replaced all three (tensioner, idler and belt) at 110K. All three were toast. Tensioner and idler bolts are 37ft/lb.
 

blackout51

Original poster
Member
Oct 18, 2012
157
CaptainXL said:
Ok, were any loose at all?? Idle rpm's are not an accurate indication of a leaking manifold. The PCM makes many adjustments to the throttle based on a number of factors. Most are not under your control. Your just shooting in the dark here. A vacuum gauge would be of great help in this case.

The bolts should really be torqued and then test for leaks using propane near the gasket sealing areas. If there is a detectable downward change in rpm or the engine dies then you still have a leak and may need new gaskets. The intake manifold has a particular torque sequence as well.

A couple I was able to tighten at least two more rotations, I followed the guide in my chilton guide as far as torquing and sequence. Something I'm becoming more suspect of it the evap solenoid by the starter, when I pulled the throttle body today, the vacuum line the runs to the evap solenoid smelled very strong of gas and all the other times I took it off it didn't smell as strong.

CaptainXL said:
It shouldn't be easy at all to pull the belt up. Sounds like you need a new tensioner. I replaced all three (tensioner, idler and belt) at 110K. All three were toast. Tensioner and idler bolts are 37ft/lb.

That's what I was thinking, that's on my list for tomorrow. I already got the new belt and idler back in october
 

CaptainXL

Member
Dec 4, 2011
2,445
blackout51 said:
the vacuum line the runs to the evap solenoid smelled very strong of gas and all the other times I took it off it didn't smell as strong.

It should smell of gas. That line has gas vapor in it. Do you "top off" when you fillup at the gas station?

blackout51 said:
I already got the new belt and idler back in october
Ok, but did you torque the bolt to 37 ft/lbs? I made the mistake of not doing this on previous vehicles and went through idlers like crazy. Chalked it up to bad bearings.
 

blackout51

Original poster
Member
Oct 18, 2012
157
CaptainXL said:
It should smell of gas. That line has gas vapor in it. Do you "top off" when you fillup at the gas station?

I know that, it just seemed a lot stronger then normal. No I don't top off usually, sometimes if I'm a few cents away from being at an even number I will but never very much.


CaptainXL said:
Ok, but did you torque the bolt to 37 ft/lbs? I made the mistake of not doing this on previous vehicles and went through idlers like crazy. Chalked it up to bad bearings.

I don't believe I torqued them, I'll check the idler while working in there
 

blackout51

Original poster
Member
Oct 18, 2012
157
Ok, new tensioner installed, and idler pulley checked and properly torqued.

I have a new piece of information, while driving with windows down alongside a stone wall, I hear this small grinding/crunching type of noise while moving, it's not the tires rolling noise, it's a different weird type of noise I've never heard before.
 

Mypetropig

Member
Dec 29, 2011
226
blackout51 said:
Ok, new tensioner installed, and idler pulley checked and properly torqued.

I have a new piece of information, while driving with windows down alongside a stone wall, I hear this small grinding/crunching type of noise while moving, it's not the tires rolling noise, it's a different weird type of noise I've never heard before.

Could be a bearing going bad in the fan clutch or water pump. I have a similar noise right now and getting ready to order the parts. With the engine off, grab the fan assembly and see if you can move/wiggle it around. Any movement at all in fan/pump shaft and its bad.
 

blackout51

Original poster
Member
Oct 18, 2012
157
Mypetropig said:
Could be a bearing going bad in the fan clutch or water pump. I have a similar noise right now and getting ready to order the parts. With the engine off, grab the fan assembly and see if you can move/wiggle it around. Any movement at all in fan/pump shaft and its bad.

I will check them tomorrow but the thing that makes me doubt that it is either of those is that it shook when the belt was off and the fan wasn't turning at all.
 

Mypetropig

Member
Dec 29, 2011
226
Did it make the grinding/crunching noise?
 

blackout51

Original poster
Member
Oct 18, 2012
157
Mypetropig said:
Did it make the grinding/crunching noise?

Well I didn't drive it with the belt off and it only made the noise when moving. But I just checked my pump and fan and they feel solid.
 

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