Dying Cylinder? (Same Problem different person)

[schoelta]

I was reading the other post, and it got me thinking of my truck. I have a similar problem. At idle the engine seems like it is missing, and there is a definite knock. However, it doesn't sound like a bearing knock as it's frequency is too slow. As I am cruising do the highway, the engine runs fine. I have also recently replace all the injectors because I didn't know the condition of the ones that came with the truck when I bought it, and I was told by someone else that the noise could be an injector knock. However, the noise was still there. I've even tried loosening the injectors to try and pin point which cylinder is making the noise, but no such luck.

So I did a compression test anyway. Here are the results:

1=425
2=460
3=460
4=410
5=460
6=420
7=370
8=460

So it looks like #7 is the one that is giving me the issue at idle. I would assume that all the other cylinders have good readings? Since #4 and #6 were the lowest, and they are right next to each other, should I be concerned about a head gasket or even head issue? I'm not loosing any coolant. What would cause #7 to be so much lower than the others? Any I looking at a complete engine rebuild, or do you guys think just doing a head/valve job would make my numbers more even across the board?

Thanks for your advice.

Tim

 

[sd2649]

way to steal my thunder!!!!! J/K. Any smoke from the exhaust? you burning oil? is your intake coated with oil on the inside?

 

[schoelta]

When I get on it hard I see a lot of blue smoke. No white smoke though, which is good. I also took off the oil fill cap, and had a lot of smoke coming out of that even when I revved the engine up. The timing of the puffs also seems to be cylinder related, but not sure which on. Based on my compression readings, I would have to guess at #7, but I'm not sure. I guess when I pull the heads off this winter, I'll find out more.

Tim

 

[Diesel JD]

Dude those readings are in spec. I would keep looking, first think is you need to pull the pass side valve cover and see what you have there with #7. A tick like that is usually either a valve problem or nothing too major. The valve problem you best catch.