I got my blown 87 TII fixed once again (twice in the last 2 months!). This time I went with a new Mazda Rebuilt block and a 90 turbo upgrade. Everything is ok, except I have a very LOW vacuum reading at IDLE, somewhere between 8-10psi vacuum! I'm sure that's way below normal, I use to get much higher vacuum readings before I blew my engine. Also once the car is fully warmed up and I try to RESTART the engine again...it has a very UNLIVELY start, after cranking it over and it finally starts, the revs go up slowly to idle @ 800rpm instead of the usual higher idle and dropping down to 800rpm type thing, which is very strange and it never did that before. The compression of new block is great at around 130 each rotor. So what can I check? I already double checked my intake system, NO leaks there. Any suggestions would be GREATLY appreciated!

 

Your readings are consistent with a lean idle mixture/vacuum leak, there is 3 of us in my area that seem to have low idle vac that we attribute to high altitude, I have never seen better than 12" of vac. If you have an a/f guage, try richening the mixture, as Mazda says, the idle mixture screw should only be adjusted after a motor change..Max

 

I live at sea level in Vancouver, so Its not likely an altitude problem for me. Should I crank the R/L mixture screw all the way RICH and see if that helps? Currently on my Air/Fuel ratio gauge, I get either a STOICH or LEAN reading at idle. Even then its a LOWER STOICH reading, instead of a high stoich, leaning into the RICH readings that I use to get before. Any other suggestions people?