Skip the auto shop - Our mechanics make house calls

Q: Engine shaking and knocking after spark plug replacement.

asked by on

I had a spark plug and ignition coil burn up. When I went to replace it the spark plug hole threads were stripped. Tapped and rethreaded and waited 24 hours before installing a new ignition coil and 4 new iridium spark plugs. When I started it, the engine was shaking badly and it sounded like something was knocking around inside.

A: This sounds to me like the cylinder head ha...

This sounds to me like the cylinder head has been severely damaged. If the burn of the coil and spark plug started on the plug end this would mean that combustion chamber temperatures from inside the engine were allowed past the electrode surface of the spark plug. The explosions from the fuel being ignited inside the engine must have caused the spark plug to burn up. I would first recommend having a qualified engine technician come and do an inspection of your engine. You may have a crack in your cylinder head. As for the knocking sound, a piece of metal from the cylinder head may have broken off during the rethreading process and fallen on to the piston. When the engine was started again the piece of metal must have been getting smashed between the valves and the piston itself. I would not run the engine anymore until the inspection is done to prevent any further damage.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Spark plug closest to firewall /on 4.0 grand cherokee has oil on it

If you are getting oil in the back cylinder then you either have excessive oil getting into cylinder from valve seals from low oil flow in the valve cover area from too thick of oil or lack of oil changes....

Q: Idle fluctuates

Hi There, It sounds like you may have a dirty or failing idle air control valve causing your engine idle to fluctuate. The idle air control valve is a small valve on the engine's intake system that reads the air...

Q: Getting horrible gas mileage.

When you say you are getting horrible gas mileage, you do not specify how bad. If another shop says it is running ok then it may be OK. If you are getting a drop of more than 2 to 3...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...