MOTOR PURR
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Since 1967
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Shipping rate is FLAT FEE $6.95 for all orders. Shipping is UPS 3-5 day ground, depending on your location. However, UPS doesn't guarantee delivery date. Orders received by 3 PM Central Time will ship same-day if at all possible. Refund Policy: Customer can request a full refund within 30 days of delivery. Physical returns are not required. If requested, refunds are issued immediately, and you may keep, donate, or dispose of the item. Return shipping fee: $0 (Free).
Rough Idle: Why Does My Engine Shake or Vibrate at Idle?
Does your car shake, vibrate, stumble, or run unevenly when stopped at a traffic light?
Does the engine RPM fluctuate, or does the engine sometimes feel as though it might stall?
These are common signs of rough idle.
A rough-idling engine may have mechanical, electrical, ignition, or fuel-system problems. But there is another possibility that drivers sometimes overlook: accumulated engine deposits.
Soot, sludge, carbon, gum, and varnish can interfere with airflow, fuel delivery, ignition, compression, and engine timing. In some cases, cleaning deposit-affected components may help restore smoother operation without replacing otherwise serviceable parts.
Is it broken, or is it just dirty?
Nine Engine Components Where Deposits Can Contribute to Rough Idle
1. VVT and Cam Position Solenoids
Oil sludge and varnish can restrict the small screens and oil passages that control variable valve timing. Improper valve timing can contribute to unstable engine operation.
2. Cam Phasers
Sludge and varnish can interfere with cam-phaser operation, potentially affecting valve timing and contributing to rough running or startup noise.
3. Intake Valves and Air Intake Ports
Carbon deposits can disrupt airflow and, in some engines, interfere with proper fuel-air mixture formation. Gasoline direct-injection engines can be particularly vulnerable to intake-valve deposits.
4. Fuel Injectors
Deposits can interfere with injector spray patterns and fuel atomization, potentially producing uneven combustion, hesitation, or rough idle.
5. Spark Plugs
Carbon-fouled spark plugs may contribute to weak ignition or misfires, especially at low engine speeds. Fouled or damaged plugs may require inspection or replacement.
6. Piston Rings
Carbon deposits can restrict piston-ring movement. In some cases, sticking rings can contribute to uneven cylinder compression and rough engine operation.
7. PCV Valve and Crankcase Ventilation System
Sludge can interfere with PCV valve operation. A malfunctioning PCV system may disrupt crankcase ventilation or introduce unwanted air into the intake system, contributing to idle problems.
8. Throttle Body and Idle Air Control Valve
Carbon and oily deposits can interfere with precise airflow control at idle. This may produce fluctuating RPM, stumbling, or stalling.
9. EGR Valve
Carbon buildup can prevent an EGR valve from closing properly. Excessive exhaust-gas recirculation at idle can dilute the intake charge and cause unstable combustion.
The Motor Purr Three-Area Cleaning Approach
Engine deposits don't accumulate in just one place. They can affect three major areas of engine operation.
Area 1 — Fuel System
Motor Purr Gas & Diesel Fuel Injector Cleaner is formulated to help remove fuel-system deposits and improve injector cleanliness through treatment in the fuel tank.
Area 2 — Crankcase
Motor Purr Tune Up uses powerful solvent-based chemistry to address sludge, varnish, and other deposits in compatible oil-wetted engine components, including areas associated with piston-ring movement and oil-controlled timing mechanisms.
Area 3 — Air Intake and Exhaust
Motor Purr Tune Up, used with the appropriate IV Tube delivery procedure on compatible gasoline engines, provides another approach to addressing certain deposits in the intake and combustion/exhaust path. Treatment effectiveness depends on the deposit location, engine design, and application procedure.
Each area requires the appropriate product and application method. Not every component can be cleaned through every delivery route.
Is It Broken, or Is It Just Dirty?
A rough idle does not automatically mean your engine needs expensive repairs. Sometimes, deposits are part of the problem—and cleaning may be worth investigating.
However, vacuum leaks, failing ignition components, defective sensors, fuel-pressure problems, and mechanical damage can produce similar symptoms. A persistent misfire, flashing check-engine light, or severe shaking warrants prompt diagnosis.
For nearly six decades, Motor Purr has maintained its commitment to strong, proprietary solvent-based cleaning formulations rather than compromising their cleaning strength simply to follow conventional additive trends.
Explore the Motor Purr cleaning approach and discover whether engine deposits may be contributing to your rough idle.