I have a 93 LT1/T-56 in my 1988 Mazda Rx-7 (yes it's lots of fun - the car weighs 2900 lbs ) I have LT4 heads, LT4 intake and a HotCam (lots of other things have been replaced as well). It has no EGR valve and the ports have been blocked with the GM export plate and a chip by pcmforless.com for the current set up. Brand new OptiSpark (switched over to the vented type)

I am having trouble with car running very rich and not idleing at all - it is hunting from 700-1200 rpm. I have Datamaster log of it idleing (or trying) if anybody is intersted. The car has no power and is really *******. I have installed new regular copper plugs and the wires are in good shape and not arching (they are newe too) and they are all connected to the right plugs - I have checked it at least a dozen times. The good news is that in the Mazda I can have the plugs swapped in about 10 minutes

No codes are being generated by the pcm - that would make it too easy.

It is acting like it has a vacuum leak, fuel pressure is 44 psi with the key on and drops to only 42 with the motor on. I have searched high and low and I cannot find a vacuum leak anywhere. I know the intake is installed properly and there is plenty of RTV squeezed out front and back. When I disconnect any of the hoses on the small vacuum ports on the intake there is NO CHANGE in motor speed, though if I disocnnect the brake booster hose it does raise the RPM - this leads me to believe that the vacuum leak is smaller than the booster port

My next step is to replace the IAC motor, it is reading between 80-100. Given the lack of a stable idle and other strange behavior

Any ideas? Thanks for the help!

 

The high IAC counts would indicate that the pcm is thinking it needs more air. The higher the count, the more air it lets in. If there was a vacuum leak, the IAC counts would be lower than normal. Now whether the IAC is actually letting in the air that is being commanded is another story. Make sure there is no problem with it sticking or it's passages are clogged.