Step by step troubleshooting automotive repair guide on how to fix an engine vibration or misfire at idle, this information pertains to most internal combustion engine vehicles.
Difficulty Scale: 5 of 10
Step 1 - If a check engine or service engine soon light is illuminated read the trouble codes, it could help point the repair in the right direction ie: fuel injector or ignition coil failure.
Step 2 - An engine
tune up
is necessary for proper operation and should be performed according to manufacturer's
recommendations.
Step 3 - Vacuum leaks are a major source of engine
idle vibrations, this is because when an engine is at idle it's depending on the
intake system to hold said vacuum more than any other time of operation. (When an
engine is under load, the vacuum is reduced.) Lift the hood and observe the
vacuum
hose system and intake gaskets.
Step 4 - An engine depends on an equal amounts
of compression in each cylinder to run smoothly. If poor compression exists in one
or more cylinders it can cause rough idle. To check for this condition perform an
engine
compression test to compare readings. Once a low cylinder has been detected
an internal engine inspection is required.
Step 5 - An intake valve must seal completely or
intake gases will contaminate the intake charge of other cylinders causing the engine
to idle rough, to test this condition a leak down test must be performed. If positive
results are produced for leakage, a valve job must be performed.
Step 6 - An engine mount is used to suspend the
engine in rubber to help eliminate vibration naturally produced while running. If
this mount fails it will allow the engine to rest against the frame of the vehicle
causing a noticeable vibration. Inspect the engine mounts for integrity, look for
any oil, cracks or separation of the mount.
Step 7 - Inspect Balance Shaft Timing
- A balance shaft belt or chain is used inside of some designs to counteract vibrations
created by the natural engine operation. Balance shafts are operated by a timing
belt/chain that can break or become out of correlation with the crankshaft either
by worn timing components or misalignment when assembled. To inspect for this problem,
remove the timing belt cover and inspect timing belt marks for proper alignment,
all engines are different, consult exact
alignment specifications. Helpful Information An engine is designed to run balanced to minimize vibration felt by the passengers
and other mechanical components. This vibration is the most noticeable when the
engine is at idle, some components are designed to help minimize engine vibration.
In remote vibration cases, a harmonic balancer or flywheel/flex plate can become
unbalanced.