it's impossible

[Tuck]

I'm tired of screwing around with the car trying to make it run right, let
me solicit your opinions.

I have hesitation at random rpm spots when the engine is under heavy load,
under light load/throttle there is no problem.  On/off throttle is a little
jerky, but my flywheel is much lighter than stock.  This is on an naturally
aspirated street port 13B in a 1987 Mazda RX-7.  Injection system is stock,
and the injectors were cleaned and balanced by Marren with the new motor
about a year ago.  Exhaust is no-cats, standard dual setup for the second
generation RX-7.

I have checked the following, or replaced it with another part for another
reason at some point or another without solving the problem:

Crank angle sensor
Leading ignition coil
Wres
Pugs
Mp sensor
Ar flow meter
Ts
Secndary injectors (the problem is only really noticable to any serious
degree above 3800 RPM, which is where the secondary injectors start firing)
ECU
Fuel pressure
Fuel pump pickup

I pulled both leading plugs yesterday and replaced them with good condition
used ones.  One of the old ones was burned much more than the other - but
they were replaced at the same time.  The rear rotor showed more lean than
the front rotor from looking at the plug, it was burned less than the front
one.  I attribute some of this to a failing coil for the leading plugs.

I have a fuel leak around my secondary injector for the rear rotor, but
this is a recent development (as in two days ago).  Bret (Rotary
Performance) and I noticed that I did not have the little sealing things
around the secondaries, so they were a little loose on the rail and that
created a vacuum leak.  We fixed that and the problem remains.  It has
slowly been getting worse for about eight months.

All of the vacuum solenoids except the fuel pressure one are physically
disconnected from the vacuum system (they were all for emissions), as is
the PCV system, and vacuum plugs are in their place on the intake.  My EGR
valve is gone, as is the ACV, in their places are block plates with
gaskets.  My throttle linkage is opening properly.  I may have a fuel leak
around a primary injector as well - but that is also only a two day old
problem if at all.

Anyone got a suggestion?


Justin "Tuck" Cordesman
SOLID BRASS-> Global Thermonuclear War can be won.

Lux in tenebris lucet et tenebrae eam non comprehenderunt.
The Light Shines in the Darkness and the Darkness does not see it.