ERAUMAZDA

Well I have been working on my other RX-7.

A 86 FC3S and I can't quite figure whats going on with the engine. It idles smooth and when you step on the gas it revs nicely with one exception. Between 1350 Rpm and 2000 RPM the engine is rough. So rough that it shakes the car. I find this very odd. If I can get it on Video I will post it.

Checked for vacuum leaks
Checked for Loose lines
Battery checked out good
Everything looks good and in check.

So any ideas.

Kenteth

Check to see if the clutch fan has all the blades. Anything unbalanced thats rotating will vibrate the hell out of a car. Even a small chip out of the fan will make it unbalanced, and a noticable vibration will be brought about. And trust me, I had to weight my old clutch fan with duck tape on 2 blades to balance it out. (and yes that takes *ALOT* of time to test it out.)

Kenteth

maybe a counterweight is missing... than again it could be about one of 300 other things. Including vacuuum leak or unmetered air.

Fingers

Is it misfiring? If so, i have the same issue, welcome to the club

Try turning the A/C on, see if it goes away. Mine does.

Failing that, it might be the steering wheel to seat interface.

SureShot

Are we talking vibration rough or misfire rough?

Kenteth

Maybe i mis-interprited. (sp?)...

Just a guess out of the blue, but fuel resistor relay? Low rpm runs lower voltage than higher rpm...

ERAUMAZDA

I highly doubt its that. It idles fine and up to about 1200 rpm.


This is something unlike to happen. If the counterweight could falloff it would throw the engine into a circular motion.

I think its a misfire....my question is possible an electrical thing. I got the car and saved it from be destoryed. I found a rag in the intake duct. I also notice the spark lines were in wrong and the CAS was moved.

If it ran rough through out the rpm band...I would feel a little bit more comfortable, however its only through a range. I may have to do a compression check.

yearrgh

Hehe. I think he's making fun of you.

Anyhow, is this when the car is under load, or revving it in neutral? Have you done the basics like replacing spark plugs, wires, etc. ?

ERAUMAZDA

underload and in neutral. I have checked the spark plugs and wires.