Vibration sitting at a traffic light

[7900_Blazer]

So wanted to run this by you all....

Engine runs smooth at all RPM's under load (driving...)...

Sitting at a traffic light though, it seem to have an idle vibration; - can see my steering wheel shake and feel it... up to about 1500 RPM... really any higher RPM and its smooths out....

Again, this is ONLY sitting...; driving, (under load...) no vibration that I can feel....

Also, this doesn't feel like an engine 'mis'... so not like a bad plug, or plug wire or something... feels like something else.

(btw: new plugs, new wires, new cap, new motor mounts, new tranny mounts)

Thoughts?

 

[Midnightmoon]

Automatic or manual? I've had clutch/flywheel issues in the past with other vehicles that have created that same vibration.

 

[Bextreme04]

Sounds like a rotating assembly imbalance, either flywheel or harmonic balancer is most likely

 

[Ricko1966]

Humor me, pull the plug wires 1 at a time at the cap,pay attention to what idle does.All 8 drop equally now you can rule out compression and ignition and start looking for something out of balance. If you do it right you won't get shocked.Take off the distributor girdle and twist and pull up on the wire from about 2 inches back.Learn this it is an excellent diagnostic tool.

 

[dvdswan]

Harmonic resonance.


How are the motor mounts?

I understand they are new. But are they solid mounts or rubber?

 

[7900_Blazer]

Automatic or manual? I've had clutch/flywheel issues in the past with other vehicles that have created that same vibration.

I'll test this at the next stop light with the clutch in... and also in neutral with the clutch out.... That should rule out any clutch issues...

 

[7900_Blazer]

Sounds like a rotating assembly imbalance, either flywheel or harmonic balancer is most likely

May not matter, but the flywheel is new - put it in when I put in the new clutch/tranny.

I have another thread here concerning my harmonic balancer rubbing the cross member. Multiple folks suggested new motor mounts... which fixed the issue... but I guess it rubbing the cross member before replacing the motor mounts could have screwed up the harmonic balancer...???

 

[7900_Blazer]

Harmonic resonance.


How are the motor mounts?

I understand they are new. But are they solid mounts or rubber?

Stock replacements... rubber within the 'clamshell'.

 

[7900_Blazer]

Humor me, pull the plug wires 1 at a time at the cap,pay attention to what idle does.All 8 drop equally now you can rule out compression and ignition and start looking for something out of balance. If you do it right you won't get shocked.Take off the distributor girdle and twist and pull up on the wire from about 2 inches back.Learn this it is an excellent diagnostic tool.

Ok, will do this when I get home from work.

 

[Bextreme04]

May not matter, but the flywheel is new - put it in when I put in the new clutch/tranny.

I have another thread here concerning my harmonic balancer rubbing the cross member. Multiple folks suggested new motor mounts... which fixed the issue... but I guess it rubbing the cross member before replacing the motor mounts could have screwed up the harmonic balancer...???

Could have... if you rubbed off too much material or it caught and spun the outer piece on the hub, it could have gotten out of balance.

 

[Octane]

Turn that a/c cooling fan down and it'll smooth out.

 

[wanderinthru]

So wanted to run this by you all....

Engine runs smooth at all RPM's under load (driving...)...

Sitting at a traffic light though, it seem to have an idle vibration; - can see my steering wheel shake and feel it... up to about 1500 RPM... really any higher RPM and its smooths out....

Again, this is ONLY sitting...; driving, (under load...) no vibration that I can feel....

Also, this doesn't feel like an engine 'mis'... so not like a bad plug, or plug wire or something... feels like something else.

(btw: new plugs, new wires, new cap, new motor mounts, new tranny mounts)

Thoughts?

Run the red lights, problem solved. Next?
Lol.

 

[Powerhouse Ranch]

i also suggest motor mounts to be checked. that'll make a worlds of a difference if that's what it is

 

[Octane]

Run the red lights, problem solved. Next?
Lol.[/QUOTEIt's all that horspower jumping at the bit.lol

 

[Zoomalot]

Was the installed "New" Flywheel for "Internally" or "Externally" balanced engine? Which do you have?
I believe both will fit, but one will not be balanced properly??