These are some that are commonly used in the automotive maintenance world and I think that before someone makes a new thread asking 'What does that mean' They should be directed to this thread, which states pretty clearly what each means.
Technical/Car related Acronyms
AC =
Alternating
Current
A/F =
Air to
Fuel
A/T =
Automatic
Transmission
ABS =
Anti-lock
Braking
System
ACT =
Air
Charge
Temperature
BHP =
Brake
Horse
power
CCRM =
Computer/
Constant
Control
Relay
Module
CEL =
Check
Engine
Light
C[K]PS =
Cran
kshaft
Position
Sensor
CV =
Crown
Victoria/
Constant
Velocity
DC =
Direct
Current
DS =
Drive
Shaft
DMM =
Digital
Multi
meter
DOHC =
Double
Over
head
Camshaft
EATC =
Electronic
Automatic
Temeprature
Control
ECT =
Engine
Coolant
Temperature
ECM =
Engine
Control
Module (a term for a car's computer)
ECU =
Electronic
Control
Unit
EEC =
Electronic
Engine
Control (a term for a car's computer)
EFI =
Electronic
Fuel
Injection
EGR =
Exhaust
Gas
Recirculation
EGT =
Exhaust
Gas
Temperature
ET =
Elapsed
Time
EVTM =
Electrical and
Vacuum
Troubleshooting
Manual
FFS =
Feedback
Fuel
System
F/I =
Forced
Induction [engine]
FN10 =
Full-size
North American Project #
10
FPR =
Fuel
Pressure
Regulator
HO =
High
Output
[H]O2S = [
Heated]
Oxygen
Sensor
IAC =
Idle
Air
Control
IAT =
Intake
Air
Temperature
IRS =
Independent
Rear
Suspension
IMRC =
Intake
Manifold
Runner
Control
J-mod =
Jerry's transmission
modification
LCA =
Lower
Control
Arm
MAF =
Mass
Air
flow [sensor]
MIL =
Malfunction
Indicator
Lamp
M/T =
Manual
Transmission
MLPS =
Manual
Lever
Position
Selector
MN12 =
Mid-size
North American Project #
12
N/A =
Naturally
Aspirated [engine]
NPI =
Non-
Performance
Improved
NOS =
Nitrous
Oxide
System/
New
Old
Stock
OBD-II =
On-
Board
Diagnostic system Rev. 2
OD =
Over
drive
OE[M] =
Original
Equipment [
Manufacturer]
P/A =
Power
Adder [engine]
PCM =
Powertrain
Control
Module (a term for a car's computer)
PCV =
Positive
Crankcase
Ventilation
PI =
Performance
Improved
RPM =
Revolutions
Per
Minute
RWHP =
Rear
Wheel
Horse
power
RWTQ =
Rear
Wheel
Tor
que
SATC =
Semi-
Automatic
Temperature
Control
SC =
Super
Coupe/
Super
charger
SOHC =
Single
Over
head
Camshaft
TB =
Throttle
Body
TC[C] =
Torque
Converter [
Clutch]
TDC =
Top
Dead
Center
TOT =
Transmission
Oil
Temperature
TPS =
Throttle
Position
Sensor
UCA =
Upper
Control
Arm
VSS =
Vehicle
Speed
Sensor
WOT =
Wide
Open
Throttle
Misc. Acronyms
AED =
Allen
Engine
Development
AFAIK =
As
Far
As
I Know
BTW =
By
The
Way
FRPP =
Ford
Racing
Performance
Parts
IIRC =
If
I Recall/
Remember
Correctly
IM[H]O =
In
My [
Humble/
Honest]
Opinion
N/m =
No
Message/
Never
mind
OP =
Original
Poster
SCT =
Superchips
Custom
Tuning
TTT =
To
The
Top
X2/X3/+1 = Showing agreement with a previous statement
YMMV =
Your
Mileage
May
Vary
Mods can we sticky this?