DJAngelicon

Engine start shaking a bit when the rpm start droping after 2K and then when it gets near 1K it will stop and idle at 900 where it normal dose. However, I think this shaking thing is all new now and I can feel it on the shift stick. Any idea what this cold be?

I have a small vide of the Rpm and Engine

Rpm --> http://media.putfile.com/MVI_1993

Engine ---> http://media.putfile.com/MVI_199428

Kentetsu

If your ignition system is working properly, then you might want to try running a very strong solution (full can in 1/8 tank of gas) of SeaFoam. Helped mine out quite a bit.

DJAngelicon

Hey Kentetsu, what is going on exacly on the car that is making it do that?

Kentetsu

Well, the way it looks from this side of the country is that you either have an ignition problem or sticking apex seals. Those are the good options. The bad options are a broken apex seal, or some other item that would affect compression.

851stgen12a

sounds like the shuder valve sticking a bit. Mine does the same thing. No biggie.
Just yoink the valve.

Todd Staples

Is it doing this when you are sitting still? If so it may be the tranny mount.

Kentetsu

Ahh, some more good ideas... Might want to check on your motor mounts while you're at it.

DJAngelicon

This only happen when I accelerate and decelerate under 2K. When is up or is decelerating from a higher rpm point it dosen't shake. Sometimes it dose shake a bit around 1.5K rpm and normaly it stop doing that around 1K rmp and it settles down at 900k. You can hear it when it kind of stay sticking before droping off. Like if my gas pedal is still push down before the engine realized that I had remove my foot from it. Not sure how to explain it but is kind of weir. It wasen't doing this two days ago unly the day I posted this in it started doing that on my way back home from the Rx7CLub BBQ Meeting.

Kentetsu

can you feel the vibration when you rev the car in nuetral?

bliffle

Sounds like the shutter valve. As it gets worse the engine starts running very rough at low speeds and makes a honking sound. Then you hafta replace it OR put a plug in the correct hole in the base of the air cleaner.

B

DJAngelicon

Only vibrates when I rev it on neutral but only dose it when it droping down from 2K to 1.1K Dose it when i am driving as well, but when the engine is idle it dosen't shake and it dosen't shake when I rev it up to 7k and let it drop until it reaches 2K that is when it dose it. Like it takes longer to drop to 1K. Almost sound like if it wants to turn off but not this is what is happening in this case.

bliffle

Remove the aircleaner lid and the filter. Look inside and you'll see a couple air holes. Put your thumb on one and see if it idles better (or put a plug in the hole). One of those is for the shutter valve and plugging it solves the problem. I actually found a custom sized plug at the JY one day.

B

DJAngelicon

Ok I will check that also but I will start maybe by checking the spark plugs, spark plugs rotor, and wires. Also thinking of cleaning the carb, and checking the fuel to make sure everything is ok. Not sure but I am hoping that is nothing to do with a rebuilt because I can not aford that at this moment. Engine should be having at least 100K to 120K on it. hopefully.

aspirao

sounds like the motor mounts . a simple soluton get solid ones and you will never have that problem

84-7GSL

Not to sound sarcastic but what are the motor mounts made out of and why do they go bad?

mR.dnA

iTrader: (1)

Think of them like a sandwich, where the bread slices are metal parts that mount to the engine and the crossmember, and the stuff in the middle is a rubber piece, which over time deteriorates and breaks or separates from the 'bread' part (or in some cases gets torn off if you've got sufficient HP )

DJAngelicon

That is an interesting way of looking at it. I am thinking of getting solit motor mounts.

twinkletoes

iTrader: (17)

I know, bringing this back. This is the same thing thats going on with mine though and plus the post isn't finished. Did you ever get this fixed? What was it? Thanks

steve84GS TII

That 2000-1000rpm decel stutter is very common on rotaries,and Im willing to bet they are supposed to do it,to a degree.Ive heard its to prevent bucking,although it kinda seems like it induces bucking sometimes.
On carbed engines,the shutter valve cuts fuel/air to the rear rotor,and another valve allows just air to enter,so as to prevent high vacuum back there.The engine is basically firing on one rotor during this time,hence the choppy sound.The EFI engines just shut off the rear injector to get the same result.

My carbed 12A did it,my S4 TII did it and my S5 TII does it.Theres a 3rd gen that goes by my work everyday and I can hear the same stutter in his exhaust when he approaches the stopsign.My brother's N/A FC and my buddies cousins's FC do it too.

twinkletoes

iTrader: (17)

Wow thats weird. Check out my other thread for an update.

DJAngelicon

Hey Twinkletoes, The problem of the shake was that on my left driver side rear tired had a lump and the right front passenger tired had a lump also. So it would dance crazy during low speed and those rpms. I am lucky the tires didn't blow up on me because they were 11 years old. So, I purchase 4 new tires and that shake was all gone. Pass your hand around each tired and check them carefully. The walls on the old tires I had was beginning to separate so that is why it made the lump and was causing the shakes.