Engine Shacking a bit when RPM Drop below 2K...
 

Original Post here ===> https://www.rx7club.com/1st-generation-specific-1979-1985-18/engine-shaking-bit-when-rpm-start-droping-below-2k-458284/

Im not even sure if this is it but maybe a motor mount?

No is not shacking all the time, it only shakes when I stop accelerating and is droping below 2K until it gets around 1100 rmp and then it gets normal and idle around 900.

My 240did the same thing and it had a broken mount

Wierd, but I kinda wanna know whats happening too. Only on deceleration when not in gear between 2k and 1k will i get that engine shaking, its like the timing is completely off for just that little bit.... but i know my timing is fine... so maybe mine is just a weak ignition?

the engine dosen't shake anywhere else only when it decelerate below 2K. Sometimes it happens during 1.5k and it change faster. However, sometimes it dose it long enough that it feels like if the engine thinks the gas pedal is still push down.

I will go today and take a drive and record what happens during the drive to see if it show something else that I might be missing there. Ya are the experts I just notice only this so I have no clue.

I had the same problem with my 85, I can almost bet cash that its the shudder valve.
You can either just deal with it, or re,ove/replace it. I had that going on for quite a while with no major issues. I am about to remove the rats nest, and the shudder valve is going with the rest of the junk.

lol, I got my tabs so I don't longer need that emission crap. lol So maybe I will remove that also. I been using for a while the air pump to the cat direct so I really haven't been using none of that emission stuff I guess.

not trying to scare you, But thats what happend when i lost compression on my front rotor. and it would not fire at low rpms.. but hell check spark plugs and comp