Hello, first time posting here. I have been researching for a few weeks now and I cannot seem to find an answer to my question. As the title mentions, I have a 2008 RAM 1500 and cylinder 7 has low compression. I want to explain what happened to cause this so you will have a better understanding of my situation. I was towing a trailer with a 99 4Runner on it, and I was leaving a friend's house after replacing the entire rear end. I was towing in the "Tow/Haul" mode that the truck offers. I was coming down a bit of a hill and approaching a traffic light. The light changed to red and I had to come to a stop pretty quickly. Being that I was in "Tow/Haul" mode, the RPMs increased to assist with slowing down to a stop. When this happened and I came to a stop, the truck sputtered and died.


I attempted to start the truck back up and it idled very rough for a few seconds and died again. While it was idling rough, I heard a pinging sound coming from the engine. At this point, I knew something terrible had happened and that I would need to have the vehicle towed to a show for further inspection. Before I could call for a tow, a police officer showed up and told me that I could not sit at this light and block traffic. I had no option but to move the vehicle out of traffic. I started the truck and again, it idled very rough and I heard the same pinging sound. I quickly put it into gear and gave it some gas and then it died again. This gave me enough momentum to get the truck and trailer off to the side of the road and out of traffic. I called for a tow and I was told that I would have to wait a few hours.


While I was sitting on the side of the road waiting for the tow truck, a random person stopped by to make sure that I was ok and that I was able to call for assistance. I briefly explained what happened and this person told me that he has a friend who is a Dodge mechanic. He called his friend and asked if he would stop by to help me diagnose the problem. He told me that his friend agreed to swing by and then he left. A little while later, the Dodge mechanic showed up. I explained what had happened and then he attempted to start the truck it idled rough and the same sound was heard and then it died. He connected his code scanner to the truck and it told him that there was a misfire on cylinder 7. He started it back up, gave it some gas to keep it from dying. When he started it again, the pinging sound was present but as he gave it some gas, the pinging sound went away and did not return after he let it go back to idling. It was now idling very rough but did not die and the pinging sound was now gone. He popped the hood and took out the spark plug for cylinder 7. We found that the tip of the spark plug had broken off inside the cylinder and was causing the pinging sound. He explained that the tip of the plug probably exited through the exhaust valve when the pinging sound stopped. He noticed something on the ignition coil (small burned spot, barely noticeable) that lead him to believe that the coil was bad for cylinder 7. He put everything back together and then swapped the "bad" ignition coil to another cylinder and then started the truck to see if a new code presented itself. No new codes came up but he recommended replacing them anyway as I did not know when they were installed. He said that since the tip of the spark plug appears to have left the cylinder, replacing the spark plugs, wires, and coils would probably get the truck up and running again. I thanked him for his help and then he left.


The truck was towed to a shop nearby and I had them replace all 16 plugs, install new wires, and all new ignition coils. After this was done, I got a call from the mechanic who told me that cylinder 7 has low compression and that the tip of the spark plug probably caused some damage while it was pinging around in there. He said he put a borescope in the spark plug hole and "it looks like a woodpecker had fun in there". He said that the tip of the spark plug might be holding the exhaust valve open and causing the low compression. I had him take off the valve cover to inspect and he told me that all of the valves appear to be functioning correctly. He now tells me that a top-end rebuild is recommended but it would be more cost-effective to find a new low-mileage engine and just swap them out.


It's been a few months since this happened as I haven't felt like dealing with it (it is a work vehicle, owned by my company, and I have a personal vehicle). I'm getting around to dealing with it now and I am wondering what my best options are. After doing some research on the interwebs, it could be an easy fix, like replacing the valve springs, or it could be a big fix, like the mechanic recommended. I'm thinking that I will do my own compression test to see what the numbers are looking like and then possibly doing a leak down test after this. The truck currently runs and drives great when not idling (like at a stop sign) at in-town speeds and highway speeds, but it does idle very rough at red lights and stop signs. If the engine needs rebuilt or replaced, I'll likely sell it as-is and just cut my losses.


Sorry for the long post, but I wanted to explain everything so you might be able to give me the best advice moving forward. TIA!

 

I don't believe you would hear the tip of the spark plug pinging around in the chamber. My guess would be something else broke the tip of the spark plug? Anyways it sounds like you are at least going to have to remove 1 cylinder head at least

 

I wish I still had the spark plug so I could post up a picture. It looked like the end of it had exploded inside the cylinder. I would like to know what might have caused this. I’m 90% sure that is what I was hearing. If not that, then what else? The pinging sound didn’t start until this happened and the truck ran great before this.

 

The pinging is anybody guess. I would suggest you heard the sound of the piston hitting a valve. Possibly from the spark plug tip holding the valve open ? You said the bores cope revealed damage inside the chamber...so something definitely is going on in there. What is the compression in cyl 7?

 

I was lead to believe that the tip of the spark plug caused the damage inside the cylinder. If the exhaust valve was held open by the spark plug tip, would the piston come into contact with the valve and cause damage? The mechanic did not provide me with any numbers from compression testing and I have not done my own compression test yet to get the readings. I was looking to do this hopefully tomorrow.

 

Chunk of sparkplug bouncing around inside the cylinder is indeed pretty loud. It is certainly something you would hear. (voice of experience there.....)

Do your compression/lead down test. See what ya get. If you have a bore scope, see if it dropped one of the valve seats.