Engine shake

[Deliver]

When the car is parked, and the hood open. You see the top of the engine (airfilter box) shaking like a stripper. What is causing the engine to shake like that? Is it normal? Should idle smooth without shaking right? I have a video of what I'm trying to say but I don't know how to post it here.

[mohammad]

just upload your video to youtube and share a link here.

Are you saying the whole airbox is shaking or just the intake horn part of the air box?

[twister77]

Welcome to the three cylinder world! No need for the video, because what you have observed is totaly normal. Most 3-cylinder engines shake quite a bit at slower speeds due to the fewer number of power strokes (number of times the cylinders are fired). This tends to even out at higher speeds and at higher engine rpm levels. Hope this helps.

[Mark]

When the car is parked, and the hood open. You see the top of the engine (airfilter box) shaking like a stripper. What is causing the engine to shake like that? Is it normal? Should idle smooth without shaking right? I have a video of what I'm trying to say but I don't know how to post it here.

It's normal. Part of the charm of a 3-cylinder engine, & you don't have to pay extra for it!

Here's someone else's clip of the engine running, & I would say it's normal/typical -

https://www.youtube.com/watch?v=EoKvKQhuBlw

[Cobrajet]

The 3A92 is a four-stroke engine with three cylinders. All 3-cylinder engines have what is called 'first-order vibration'. This is when the engine tends to shake not from side-to-side, but from end-to-end. If you take two inline threes and put them end-to-end on the same crankshaft the shake completely disappears. Inline sixes are the smoothest engine configuration around. There are three main ways to deal with shake in a triple.

One is to install a flywheel with it's weight offset to counteract the shake, as with the Ford 1.0 Ecoboost. This is why the 1.0 was initially only available with a manual trans.

Another is through engine/trans mount materials and design. The engine will shake, but the way it is mounted will minimize the amount of vibration transmitted to the chassis. This is done in the Mirage.

The other is through the installation of somewhat complex and expensive counterbalance shafts, which add so much weight/complexity/expense and sap so much power that they tend to make the 3-cylinder engine make less sense compared to a 4-cylinder engine.

The shake has led a few reviewers to somewhat derisively call our car the "Mitsubishi Massage".

[Basic]

You know, at this point, one of us should have been brave enough to hack a big hole in the hood and install a functional "shaker" hood scoop...

[davidricardo86]

One of my favorite things about the 3a92 is it's distinct sound! The factory exhaust notes reminds me of a Subaru boxer engine. Maybe I'm just hearing things but I would love to hear a 3a92 with ITBs, big cams and a tuned exhaust!!

I have to admit i too was shocked and appalled by the 3a92's rocking back and forth. I was used to seeing 4 cylinder engines, I'd never seen a 3 cylinder engine moving like that. But it grew on me too, and now it looks normal.

[Mark]

One of my favorite things about the 3a92 is it's distinct sound! The factory exhaust notes reminds me of a Subaru boxer engine. Maybe I'm just hearing things but I would love to hear a 3a92 with ITBs, big cams and a tuned exhaust!!

I have to admit i too was shocked and appalled by the 3a92's rocking back and forth. I was used to seeing 4 cylinder engines, I'd never seen a 3 cylinder engine moving like that. But it grew on me too, and now it looks normal.

I say if it shakes for 300,000+ miles, who cares?