engine and drivetrain Reasons Engine shakes so much?

[Guest Anonymous]

On Thursday, I snapped the lower motor mount at the piece of metal that attaches to the mount itself, on the driver side. I had to bring it to work to get it fixed. Anyway, I have notcied that the engine shakes quite a bit. While sitting at a stoplight it is very noticeable. While I was at work, we checked the mounts etc. and they all seemed to be fine (except for the obvious break). You can actuallly see the car shaking while its just sitting at idle. Now, what would be the reason for this, besides motor mounts(which I am still going to replace). Could it have something to do with the cross member itself? Or what about something wrong with the motor internally?( Even though I think it has something to do with engine support). Thanks for any help.

[Guest Anonymous]

is it running on all cylinders, do you have dual carbs that could be out of sync

[SteveH]

Even with dual carbs, it should idle pretty smooth. You should not see the whole car shaking, but you will feel it inside the car. First we need to know which carb(s) you have.

EDIT: If this if WTA, you have sidedrafts, correct? Be sure the carbs are synched properly. After that, pull the plugs and see if the color is even between all four. Then, replace the plugs, start the car, and slowly (with proper insulation from the ignition sytsem), pull off one plug wire at a time. If you pull off a plug wire and the engine doesn't respond, that cylinder is misfiring.

Points?

Plugs?

Cold start enrichment device (some call it a choke) stuck on? This was my problem. A part was broken and one cylinder was set for cold start. I was able to see this in the plug check as one plug being totally fouled and black.

Mixture screws set properly?

Bad plug wire?

Idle jets tight and unclogged?

[Guest Anonymous]

Yeah, its me. I can't remember my password for WTA so Ive been using this. I think it has pretty much been shaking this bad since I got the car, when it had a weber 32/36. Now with the duals, I still can't pinpoint what it is. Im prettty positive its running on all four cylinders, unless I have been driving around on 3 the entire time.

[_z_]

you can always pull one plug at a time and see if the engine doesn't change

[KFunk]

I've had the same thing since I bought my car...

Since then, I changed the motor mounts, rebuilt the head, tuned the carb the best I can with Redline instructions and CD prescription, fixed all leaks, changed everything in igniton system (but still points, no pertronix yet), changed tranny mount, guibo, CSB, etc.

It still shakes at low idle.... but the car seems to drive just fine at any higher RPMs. Someone else on the forum had the same problem, too.

All pistons are intact and doing what they should, because I could see them while I had the head off.

My best guess is that something is knocked out of balance on the crankshaft. In that case, I'll just drive it till it blows up.

The motor mounts, tranny mount, and strengthened center support bearing (with fuel hose wedged in ring) helped limit the bounce. (the damper around my old bearing was ripped out and allowing whole drivetrain to bounce a little).

While its minimized, its still there. The gear shift bounces side to side a little while idling.

My last wild hope is that maybe my weak alternator could contribute. It hasn't been giving me enough voltage to even make my turn signals flash while idling, so maybe its not giving enough power to the ignition system at idle. I've got a new 320i alt ready to go on, and will try to do it tomorrow.

[Guest Anonymous]

Mines exactly the same. It has no running problems at all once you get going, but at idle it shakes. It will be intersting to see if your alternator does anything.

[TheWolf]

try to take a look and inspect the drivers side mount steel frame piece and you should find that it has cracked by the steering box... thus the shaking... weld and fix.

[KFunk]

i'll look tomorrow, but don't think its that easy for me. You can see the engine mount distorting back and forth as it absorbs most of the bounce. The frame looks to be holding strong, while the engine mount rubber bounces all over the place. While it absorbs some of the bounces, the net effect is a light shake of the whole car.

I didn't get the chance to put the new alt on today, since it didn't come with a pulley, so I gotta get an impact wrench and swap pulleys. I'll do that tomorrow. Its a long shot and I don't know much about electrical systems, but would be cool if it could fix it.

[KFunk]

I'm not 100% certain, but I think the alternator may have solved it!

At first there was no effect, but once it got warmed up after driving for a little bit, the voltmeter finally got close to 14, the engine became very smooth.

There's still a very slight shake, but I don't see the big wobble I had before.

No, there weren't any cracks around the driver's side engine mount. The engine side of the mount shakes more than the frame side.