How Carbon Deposits and Rich Fuel Mixture Cause Valve Sticking – Diagnosis & Fix

The first sign of sticking valves is usually, engine misfires or running rough when cold.

However, sticking valves can also be, the byproduct of cold weather operation.

In this case, the sticking valves will often work free, as the engine warms up. Thats why, doing a cylinder leak down test when cold, can confirm if this is happening.

Sticking valves, can also be a sign that there are, carbon deposits on the valves.

Carbon Deposits Can Form On Your Valves For A Number Of Reasons

Often carbon deposits are the result of a rich fuel mixture. It can also be the result of oil passing through, a worn valve guide. So, oil is pulled through the intake valve guide and into the combustion chamber where it’s burned. But, on the exhaust side, a worn valve guide can allow oil to sit on the valve and form deposits.

A loss of compression, poor combustion or cold engine operation can also cause carbon deposits to form on the valves.

Extremely worn valve guides, can also result in sticking valves. But, they are more likely to manifest as engine misfires or spark plug fouling, before actually sticking.

Sticking Valves Can Also Result In Bent Valves

So, the most common failure of valves, is bent valves. As a result, of contact with the pistons. The valves contacting the top of a piston is due to incorrect engine synchronization.

Because, the valve is held open, at the wrong time.

Other Possible Causes Of Bent Valves Include:

• Sticking Valves, From Carbon Build Up.
• Timing Chain/Belt Breakage.
• Incorrect Installation, Of New Belts and Chains.
• Weak Or Broken Valve Springs.
• Engine Overheating.

So, if you suspect your engine may have bent valves, it is crucial not to attempt to start the engine.

Sticking Valves Can Also Cause Them To Burn

The other common type of valve failure, is burnt valves. Essentially this is caused by combustion gases escaping between the valve and valve seat, when they are not sealing correctly.

Normally, this type of failure affects the exhaust valves only. But, it can also damage the intake valves.

To Help Prevent This Type Of Failure, There Are A Few Things You Can Do:

• Maintain a clean, efficient cooling system, so the engine does not run too hot.
• Use good quality fuels, to help prevent carbon build up on the valves. And, regularly check the valve clearances.
• Irregular valve sealing with cylinder head valve seat.
• Carbon residues generated by irregular combustion will threaten the sealing, between the valve and its seat.
• Incorrect valve clearance, can threaten the valve sealing, causing this type of failure.
• Running a dry fuel, such as L.P.G resulting in inadequate lubrication.
• (EGR) Valve Issues.

Deposits can travel to other areas of the engine and cause problems. Because, engine deposits build up slowly, you can go a long time without noticing they’re there. Eventually, they will rob your engine of its power, and can cause serious hesitation and stalling, if left unattended. As a result, causing sticking valves.

Minimizing Carbon Deposits

Thank You!