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New motor mounts - motor still bounces around quite a bit

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Greetings all,

 

 

At an idle my motor has a lot of movement. Just sort of wobbling and bouncing all over the place.

 

After just replacing the motor mounts, we are none the better.

 

I am starting to wonder if it could be the valves need to be adjusted, so I am ordering a new VC gasket and planning to check them out.

 

I have an electronic ignition. Runs great, but idle is not ideal. Carbs nice a shiny.

 

Any other ideas?

 

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CarbS? Have you tried syncing the carbs? getting the ide mixture correct? ignition timing? Plug wires? Plugs? Valve adjustment?

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(edited)

sounds more like a timing issue, or maybe a rear tranny mount issue.

youre motor at idle should not be bouncing around regardless of the motor mounts

 

not sure valves would be the issue. 

‘If I we’re you I’d go back thru the timing procedure for your ignition step by step, and then the fuel system

 

and as turbo mentioned, spark plug wires and plugs. 

Edited by gwb72tii
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4 minutes ago, Preyupy said:

CarbS? Have you tried syncing the carbs? getting the ide mixture correct? ignition timing? Plug wires? Plugs? Valve adjustment?

Carb. Just one.

 

Ignition timing makes no difference. New plug wires. New plugs.

 

I was thinking valve adjustment.

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Look carefully at the bracket that the driver's side engine mount attaches to.

They are known to crack.

This one had the crack welded and some reinforcement added.

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I think your first thought is a valid one.  Valves.  But before you pull the valve cover off, consider checking compression.  It is a fairly easy process with a $20 tester or maybe even one you can borrow from your local parts store.  Crimp or disconnect the fuel line, disconnect the coil, screw in the pressure gaue and crank.  A difference of, what, 10-20 PSI in one cilynder is enough to make the engine rock a little.  Some of the other suggestions would come with other symptoms besides a wobbly engine.  I had a '76 530i that ran wonderfully except for a hellatios wobble.  It was one whacked exhaust valve.   

 

Keep in mind also that even perfect 4 cylinder engines aren't perfectly still when running like a lot 6 or 8 cylinder engines might.   

 

Oh, another thing you can do is listen to the exhaust at warm idle.  Hear an inconsitent pop or gurgle sounds?   In my experience, that's an exhaust valve openng too soon or not closing all the way.  

 

And lastly, hot cams like a 292 might make your engine wobble a bit more at idle even when properly adjusted.  If you have a 292, you might just have to live with it.  

 Hope that helps! 

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I agree with some of the above suggestions. Make sure all cylinders are providing equal performance (compression test) and make sure the carb is jetted / tuned properly. Check for vacuum leaks (especially on the cylinder / hose / check valve providing vacuum to the brake booster!)

 

Intake / exhaust valves that are a little too tightly adjusted will also affect smooth idle.

Firmer motor mounts will definitely transmit more vibration to the chassis, steering wheel, and stuff under the dashboard (rattles / buzzes), as well as stressing out the weak point on the subframe, where the driver's side mount goes (near steering box). 

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When I bought my car from the P.O. I was equipped with Urethane hard mounts and vibrated through the chassis until my passenger side disinigrated. 

I replaced both sides with the stock soft mounts and added a TEP strut brace with motor support, vibration and rocking both eliminated 

 

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8 hours ago, Hodgepodge said:

It is a fairly easy process with a $20 tester or maybe even one you can borrow from your local parts store.  Crimp or disconnect the fuel line, disconnect the coil, screw in the pressure gaue and crank.

 

...And be sure to open the throttle to full when you do that.

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One of my regrets in my recent rebuild. I used the green urethane mounts for motor and tranny and wish I would have used OEM BMW rubber mounts. I just get a little too much vibration inside the car for my liking. Well.... next time around, although, I think the three mounts could be surgically replaced without dropping the motor/tranny.. but i have to do a little reading on that idea.

 

Randy 

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I've replaced both mounts, one at a time, with a floor jack (and a board) under the engine.  There is a moderate amount of "play" when lifting the engine, more than enough to get the mounts in.  I have not replaced the gearbox mount with the gearbox in the car, but I don't think it would be impossible to replace from underneath since you can see the mount pretty clearly.   Without looking, might make sense to but a jack under the gearbox, remove the brace, replace the mount and replace the brace.      

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(edited)
17 minutes ago, worzella said:

One of my regrets in my recent rebuild. I used the green urethane mounts for motor and tranny and wish I would have used OEM BMW rubber mounts. I just get a little too much vibration inside the car for my liking. Well.... next time around, although, I think the three mounts could be surgically replaced without dropping the motor/tranny.. but i have to do a little reading on that idea.

 

Randy 

 

 

I recently purchased a Engine Cross Bar from Harbor Freight for about $68, easily lifts the motor up about 7” so you could swap out motor mounts or change a pan gasket 

 

the nice thing about it was how you can slowly drop the motor back down to align the motor mounts, it worked better for me than a conventional Cherry Picker lift 

 

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Edited by chargin
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Lash the valves, check compression,

then work on the ignition.

The m10 is quite sensitive to timing and scatter-

an older distributor lets spark wander, and idle goes to 

pot in a hurry.  

 

t

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1 hour ago, worzella said:

One of my regrets in my recent rebuild. I used the green urethane mounts for motor and tranny and wish I would have used OEM BMW rubber mounts. I just get a little too much vibration inside the car for my liking. Well.... next time around, although, I think the three mounts could be surgically replaced without dropping the motor/tranny.. but i have to do a little reading on that idea.

 

Randy 

 

Really easy to replace if you have a engine cross brace ($75 from harbor freight). Probably would take an hour at most.

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Before you go through a whole round of troubleshooting....do realize that these motors move around on their mounts quiet a bit more than other cars of their era (or most other cars for that matter!)The engine rocking on its mounts at idle is quiet normal. Can you post a video of what your looks like at idle?

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