An engine surge is usually caused by a fuel system management or drivetrain failure.
The fuel management system utilizes sensors that monitor emission output and engine
performance are communicating with the main
ECM (engine
control module) controlling fuel mixture, timing and emission management systems.
While the engine is surging the ECM is "hunting" by adjusting the fuel mixture and
timing. These adjustment are made by the ECM in a isolating manner as the ECM tries
to satisfy its coordinates. These coordinates are not satisfied because of a system
malfunction, we have listed some of the most popular problems and repairs below.
Troubleshooting Procedure
B.
Testing Fuel Pressure: Test for proper fuel pressure with a fuel pressure gauge.
Connect the gauge to the test port on the fuel rail. Fuel pressure reading's very
depending on the system your in our vehicle, but most throttle body injection cars
(TBI) are between 13 psi and 17 psi. and most (DPI) direct port inject systems are
between 40 psi and 55 psi. To find out your vehicle system fuel pressure consult
a
repair manual. If little fuel pressure is present the fuel pump needs to be
replaced.
C. Plugged Fuel Filter: A
plugged
fuel filter can cause an engine to surge. The fuel system supplies power
to the
engine through
combustion, if fuel can not be delivered it will cause inconsistencies
in performance. To check for this condition remove
fuel filter and inspect, replace
with new unit and recheck.
Fuel Filter Removal
D. Check Engine for Vacuum Leaks: If an
engine vacuum leak is present
it will cause the sensor input readings to the
ECM to be incorrect causing an engine surge. The system is programmed to work
at prescribed value. When a vacuum leak is present these readings are incorrect causing
the engine to surge under power and idle rough. Inspect the air intake boot for
tears and vacuum feed lines to all accessories. Replace torn or dilapidated hose
with a new hose and recheck system. Also an IAC (Idle Air Control) valve bypass
hose it can develop tears/holes mid way through the hose, inspect thoroughly (common
problem on Ford trucks and SUV's) Sometimes a vacuum leak can be detected by opening
the hood, start the
engine and allow to idle, then listen for an audible whistling
sound. Then inspect that area of the engine compartment to locate leak.
E. Check for Plugged Exhaust System:
The
exhaust system in your vehicle is designed to release exhaust gases from
the engine to the rear of the car. This system is designed to have about 3 pounds
of exhaust backpressure under full throttle. This means the engine should not have
to push more than 3 pounds of pressure to release the exhaust at any given time.
If a
catalytic converter plugs or breaks apart it will plug the exhaust system causing
an engine surge.
Plugged Catalytic Converter
F. Test for Weak Ignition
Spark or Failing System:. A weak
ignition system can be a sign of a failing
ignition component and cause the engine to surge. Remove spark plug wire and insert
an extra spark plug into end of wire, attach spark plug to engine ground then crank
engine. You should observe blue spark between spark plug gap. If a yellow spark
is observed, your
ignition coil is weak and needs to be replaced. Also the spark
should flash in a constant rhythm, if the spark is inconsistence suspect the crank angle
senor, ignition coil or ignition module.
G. Check for Automatic Transmission
Clutch Slippage: When the clutches inside a
automatic transmission start to
wear they can malfunction. This condition will deliver a surging or a tugging sensation
to the driver. Without taking the transmission apart it is impossible to check
the wear of the clutch discs. But there are tests that can help you in the repair
diagnosis, first remove transmission dip stick and inspect the condition of the
fluid, if the fluid has a burnt smell and is dark color instead of the normal red
color the fluid is burnt. The transmission fluid is a hydraulic fluid that when extreme
heat is applied to the fluid condition becomes burnt and smelly. The extreme heat
is generated from the clutch discs slipping. Sometimes a
transmission service will
help the operation by removing the burn fluid and replacing it with new.
Automatic Transmission cut-away Image
H. Check for Standard Transmission Clutch Slippage: When a clutch assembly
starts to wear it can cause a
engine surge sensation. This is caused by the clutch
pressure plate loosing tension and allowing the clutch disc to slip against the
flywheel. The clutch assembly is a normal service item and need to be inspected
between 60,000 and 80,000 miles. If the clutch peddle is at the top of its travel
with no free-play this is a sign the clutch assembly is worn out needs replacing.
When servicing a clutch disc always replace the clutch disk, pressure plate, throw
out and pilot bearings (note: some transmissions do not use a pilot bearing). The
flywheel is the component the clutch assembly bolts to, the clutch disc is in direct
contact with the flywheel and clutch pressure plate.
Clutch and Flywheel Assembly
Troubleshooting
/ Engine Surges
Check Manufacturer Specific Engine
Surges Questions and Answers
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