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Melted valves happen when it’s not closed all the way. Could be carbon buildup or bad valve lash. Ive had this happen in my old acura mdx.
But that picture is the older 3.0t version. The 4M is equipped with the port fuel injection to clean the valves and it does its purpose. When I replaced my pcv valve at 120k miles, the valves were shiny and clean.
The burned valve is an exhaust valve. And yes agreed MPI has the maintenance overhead of two sets of injectors but is an excellent long term solution compared to periodic cleaning of DI valves.
The burned valve is an exhaust valve. And yes agreed MPI has the maintenance overhead of two sets of injectors but is an excellent long term solution compared to periodic cleaning of DI valves.
Did the valve material fracture or disintegrate? Is the seat damaged? It almost looked like there were remnants on the seat but could simply be dirt too.
If the valve fractured then the missing piece is likely resting up against the cat and may cause rattles.
All stock. I replaced the valve and the seat was fine (I ground it perfect).Maybe I lucked out. Still in the process of stabbing it back in
Last edited by gbgastowers; 12-18-2023 at 08:19 PM.
Melted valves happen when it’s not closed all the way. Could be carbon buildup or bad valve lash. Ive had this happen in my old acura mdx.
But that picture is the older 3.0t version. The 4M is equipped with the port fuel injection to clean the valves and it does its purpose. When I replaced my pcv valve at 120k miles, the valves were shiny and clean.
My belief is that the pcv valve failed around 100k and it started letting oil into the cylinder which caused excessive carbon buildup on exhaust valves. A piece of carbon welded to the valve and caused it to stop spinning (usually rotates 360/min) and prevented contact with cylinder head to disperse its heat. Meltdown was the result with loss of compression. Bores looked beautiful
Last edited by gbgastowers; 12-23-2023 at 07:27 AM.
I would want to to see bore scope pictures of the zero compression cylinder. If the valves are damaged causing zero compression then the engine can be repaired. If the cylinder wall is damaged then the engine is not repairable.
The number one cause of cylinder wall damage is a long term undetected stuck open fuel injector. To help avoid a stuck open injector, the manual says to periodically add a Direct Injection Cleaning Additive to a full tank of premium fuel. Do you happen to know if injection cleaning additive was used?
I wonder how often "periodically" means? Thanks for mentioning this additive. My car is at bout 60K miles, which I'm sure is well past periodically. I'll order some.
I wonder how often "periodically" means? Thanks for mentioning this additive. My car is at bout 60K miles, which I'm sure is well past periodically. I'll order some.
Every now and then I do it once/twice a year. Usually I use chevron. Throw a couple of bottles.
Melted valves happen when it’s not closed all the way. Could be carbon buildup or bad valve lash. Ive had this happen in my old acura mdx.
But that picture is the older 3.0t version. The 4M is equipped with the port fuel injection to clean the valves and it does its purpose. When I replaced my pcv valve at 120k miles, the valves were shiny and clean.
Port injection will help to keep the intake valves clean but I doubt it's doing much to help on the exhaust side. In the case of the picture the valve that is burned is the exhaust because, as you say, it's not seating 100% and allowing the hot gas to leak past it. As "gbgastowers" mentions this could be due to a PCV that wasn't doing a good job of air oil separation causing oil laden air which produced build up.
Originally Posted by tomaszp72
Every now and then I do it once/twice a year. Usually I use chevron. Throw a couple of bottles.
I use Driven Injector Defender or Chevron Techron CFSC -- anything with PEA will do. For the Techron the ratio is 1 oz : 1 gallon gas when your tank is half full or less, so it mixes well.
I use Tier 1 premium fuels and add a bottle of injection system cleaner with a fuel fill once every 5,000KM. Adding the bottle first then fill the tank helps ensure a good mix. The bottle in my pic is sized for one full tank. There are no guarantees but when it works then it can save the engine from catastrophic cylinder damage.
The quickest zero intrusive method to periodically test for stuck open injector is monitor fuel rail pressure after engine shutdown and watch for a fast bleed down condition. My fuel rail pressure rises after shutdown due to engine bay heat bloom and takes several hours to slowly fall. I have graphed pressure vs time so I know what to expect. If an injector is open then pressure will fall abnormally fast. To identify which injector(s) are leaking, I pull spark plugs soon after shutdown and insert a rubber tube thru the spark plug hole, blow in a tiny bit of air and sniff test what comes out. If you smell raw fuel then the injector is leaking. Sometimes depending which intake valves are open by coincidence after shutdown then two cylinders may smell of fuel, either because more than one injector is open or fuel vapor migration thru the intake crossing cylinders. A well timed bore scope inspection can also show a fuel fogged wet cylinder if you need proof.
I hope this information helps save some engines from an avoidably early fate 👍
Last edited by AudiAllTheWay; 12-20-2023 at 08:29 AM.
12-18-2023, 02:51 PM
