1987-91 Mazda Turbo II info:    		Updated 11-14-96

* General overview *

The rotary turbo cars are great, proving lots of smooth power, average 
sports car mileage, good handling, and attractive styling.  Although like
all modern high performance cars, must be meticulously maintained to insure
reliability, longevity, and performance levels.  The relatively high 
cost of some parts on Japanese cars stops many from properly maintaining, 
usually resulting in otherwise unneeded repairs and problems. A plan of 
regular interval service, fluid changes, and proper cool down and driving
habits are key in keeping cars on the road.  Many engine failures can be 
blamed on lack of maintenance, oil starvation due to leaks, or 
overheating due to coolant leaks or circulation restrictions such as 
thermostats or radiators. The rotary engine does not like to be overheated.  
Just one full scale overheating can warp expensive 
housings or at least damage coolant gaskets. The combination of several 
different types of metals, iron housings and aluminum/cadmium alloy rotor 
housings found in the engine, results in uneven expansion/contraction 
characteristics. 
	The Mazda factory shop manual is mandatory in order to understand
and repair car properly, and worth every dime.Understanding the repairs 
and why necessary saves lots of money and wasted time by avoiding trial 
and error parts replacements, and buying things not needed to repair 
problem.

* Basic turbo car information *

  A turbo timer is one of the most inexpensive ways to prolong engine life.
Allowing the oil to circulate thru turbo after driving for couple of
minutes, allows the hot oil to be cooled, instead of just "cooking" in the
turbo & engine housings.  Also, avoid engine speeds over 3000 rpm until 
engine is at normal working temperature.  Oil changes at regular intervals, 
based on driving habits are also very  important.  The more time in
boost, the shorter the plugs and oil change intervals need to be.  This 
is especially true if driven aggressively, or car is used for racing 
purposes, where constant hi-rpm & boost levels are maintained. 

* Steps for durability, keeping engine in 1 piece *

Higher boost levels also require intercooler upgrades and fuel enrichment 
for longevity.  The stock systems are designed to provide ingredients 
for 200hp, at 6-8 psi.  Common modifications can double boost pressures, 
increasing heat and rate of wear of internal engine & turbo parts.  The 
turbo cars do have lower compression engines, but also have 2mm apex seals.  
They are designed 
to seal better than the older 3mm seals, although the higher boost 
increases temperatures, therefore weakening metals, eventually leading to 
cracking.  Larger intercoolers and additional fuel lower combustion 
temperatures, increase power and maximum boost levels safely able to use.  
Again, the high cost of air/air intercoolers ~$1500 scare people away, 
but much than the cost of a new engine.  Cars over 220 hp or so tend to 
run lean with factory injection, increasing temperatures and 
chance of detonation.  Aftermarket EFI computers, larger or additional 
fuel injectors, and timing retard computers drastically increase longevity, 
as well as allowing for more safe boost, increasing power.  A rule of 
thumb is 1 extra psi of fuel pressure per pound of boost.    Switching to 
3mm apex seals is expensive, but also increases durability in extreme 
conditions.  Oil pressure should be increased 15-20% as well.  The turbo 
cars already have higher flowing oil pump, so only need to replace the 
regulator.  93 octane fuel is required, and 2 cycle oil premix is great 
for additional protection, and is added to fuel tank.  Oil changes using
factory filters and Valvoline or Castrol GTX 10w30 or 40 is recommended 
every 3000 miles.  Some people prefer to se synthetics or blends, benefits
and drawback opinions are widely varied, so that decision must be made by 
the owner.  Synthetics do tend to amplify oil leaks in some cases, again, 
largely based upon individual experiences and not tested in controlled 
environment.  High boost cars tend to cause some oil system contamination 
from gas pressure forcing way into oil passages, and will require more
frequent changes.
     
* Ignition system *

Ignition is often overlooked when modifying cars, when in fact one of the 
most critical factors.  Anytime increasing the air/fuel flow, additional 
spark is required to burn mixture.  Also, timing retard systems and knock 
sensors help.  Plugs should be replaced often if lots of boost and/or use 
for long duration's.  Ignition computers such as Jacob's, MSD, Crane 
increase spark intensity many times, and is a must for any modified car.  
For ignition wires, there are many types; do not use the 
cheap $10 ones, they will fail, and are not water proof.  Tend to pop 
off connections, resulting in damaged ignition components and possibility
of underhood fire.  The factory NGK are the most 
reliable, inexpensive, and fit right.    Timing does not vary on these 
cars, and does not normally need adjustment, unless previously set wrong. 
Ignitor/coils do fail, as well as the ignition key switch, although not 
very common.     

* Turbo idling problem areas: *

The high underhood heat on turbo cars causes problems not prevalent on 
non-turbo cars.  Vacuum hoses, rubber boots, hoses, and plastic parts turn
hard & brittle, usually resulting in vacuum leaks, running problems, and 
fluid leaks.  Most common vacuum leak is the turbo inlet duct, large rubber 
tube running from air box to turbo inlet.  Cracks under the hose clamp, 
usually on bottom side, can be hard to detect, air pump obstructs view, 
so the duct should be removed for inspection.   Also the small lines all 
around the turbo also crack.  Cars with higher boost levels tend to pop off 
intercooler lines, as well as other vacuum lines.  Air flow meters are 
pretty reliable on these cars, unlike Nissans, unless suck in debris from 
using cheap air filter falling apart (Purulator, white paper ones 
or RB foam green) or inhaling outside flood water.
	Tune-up parts, especially plugs should be replaced on regular 
intervals.  For stock cars not driven hard, 15-20k on plugs is ok.  For 
modified cars that see lots of boost & rpm, 1000-10,000 is 
maximum allowable safely.  When the plugs start to deteriorate, the ceramic
portion can crack and fall into engine.  Always use the NGK BUR7(9)EQ 
plugs, NEVER the SD type, discontinued on 87 due to cracking problems.  
The platinum BUR7(9)EQP plugs can be substituted (recommended) for 
improved durability and "crisp" performance that lasts longer than the non-
platinum versions.   Ignition wires should be checked for resistance 
periodically, replaced if above 8k or so, or if any physical damage such as 
corrosion on boots, frayed shielding, oil/fuel contamination, or loose 
fit.  See ignition section above for additional information.

* Throttle position sensor    TPS *

The throttle position sensor will regular adjustment as well, part of the 
tune-up procedure.   Misadjusted TPS is often characterized by repetitious 
pulsing revs at idle.  The TPS is often blamed, and replaced, when 98 % of 
the time is only a simple adjustable, or other problem such as 
sticking throttle cable, not allowing throttle bladed to return to idle.  
The 89-91 t-ii's have a self adjusting TPS, and should not need messing 
with.  TPS has to be adjusted at full operating temperature, and is easily 
adjusted using a light set, not as easy using the voltmeter method as 
outlined in the shop manual.  A plug in light set is available for 
$20, makes adjustment a snap.

* Thermo wax problems *

This item, located on back side of throttle body is responsible for setting 
cold running idle, and gradually reducing idle when warm.   Cars with 
corrosion or buildup around throttle body are more prone to have 
problems, as well as ones that have not had coolant flushed on regular 
basis.  Also, buildup in throttly body passages leading to the T-W sensing 
false temperature, due to lack of coolant  circulating.  Also, the small 
EFI coolant hoses going to and from the engine and throttle body tend to 
bulge and leak.  A car running too hot or cold will also tend to run 
poorly as well, and should be modulated with factory thermostat.

* Flooding problems *

	The 86-91 fuel injected cars are prone to flooding by nature.  Can 
be as simple as old plugs or ignition wires, to as complex as intermittent 
EFI computer malfunctions.  

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*	The most common problem is not really a defective part *or failure, 
but a "bug" found in the EFI system.  If the  *car is started, allowed to 
run for only a few minutes, *turned off,  then attempted to restart later, 
it will *likely flood.  Even if everything else on the car is *perfect, this 
problem cannot be explained, or "fixed", just *have to learn to avoid the 
situation, or install anti-flooding module outlined in next section.   
Everytime the car *is started, must allow to fully warm up before turning.  
Common *story is moving the car from driveway to garage, only *running for 
few seconds, next morning cranks, but not *starting.     
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Mechanical problems such as low compression due to high mileage or 
dirty/leaking fuel injectors contribute to the problem. Electrical problems 
such as slow cranking speed due to weak alternator, bad battery/ground, or 
starter can result in too much fuel being injected, saturating the spark 
plugs.  If an engine has been severly overheated, may be inhaling coolant 
into cylinders, characterized by white smoke on startup.  Higher mileage 
models may have weak oil seals, causing oil to seep into cylinder while 
car is sitting, and smoking (blue) when started or held at continuous high 
rpms for several seconds.  Only repair for both is engine replacement or 
overhaul.  On automatic transmission cars, similar symptoms appear when 
the vacuum modulator diaphragm goes bad, resulting in ATF inhaled into 
the engine under high vacuum situations.  A rare but possible problem 
is the malfunction of the sub zero fluid system injecting antifreeze into 
engine under above 0 F conditions, fouling spark plugs.  This system 
should be tested or removed to avoid potential problem, unless climate 
conditions otherwise warrant use.    
	Other common problems include defective Air Control Valve solenoids.   These 2 parts are 
located on ACV, and will commonly internally short, sometimes causing wire 
harness damage from melting insulation, or send false signals to EFI 
feedback system.   

* Precision Imports EFI computer anti-flooding module *

	Due to the number of flooding problems these cars have, we have 
developed an electronic module that works in conjunction with the EFI 
computer, allowing for any fuel in the engine to be expelled before 
injecting more.  This process is automatic, and does not affect the car in 
any other way.  Essentially the same thing as manually pulling the EFI 
fuses under hood, when trying to get flooded engine started.  Easy 
install, prevents flooding in 99% of all cases,  whether due to definite 
low compression or leaking injector problem, often delaying or eliminating 
need for expensive repairs.  Additional details available upon request.

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more to follow, will be on web page under tech diagnostics section soon