Lately when I'm at stops with 85' Rx7,w/ a 12A, the engine idles strange. The RPMs don't drop, but the readings on the compression guage do. I already knew that this engine had started to lose compression, a Mazda dealer ran a compression test when the had its inspection done, which it passed. At first the compression guage itself never we read above 60, but the more I drive the car the better it seems to run and the higher the guage reads. Its got new NGK plugs and NGK wires.



The idling problem at first was a result of two vacuum lines that were disconnected. The car would not idle on its own without constently giving it gas. Now the idling problem is that at stops the engine sounds choppy and the car itself shakes a little. If you listen the car from the outside the car sounds like helicopter and the exhaust sputters and makes a clanking/clicking noise(while the engines running) like some older japanese do after they're shut off. The car only runs like this when either its at a stop or warming up. I'm not sure if the engine getting ready to go or if it might be another problem. I have noticed some white smoke lately, but I doesn't seem any different from the condesation smoke that I have seen from my other cars. This is my 5th Rx7 and I have never seen an idling problem like this. If its the engine than I guess I'll have the move forward with the 13B swap.

 

Check that the coasting valve hasnt rusted itself shut, mine did it and it ran like dogshit untill I bypassed it.