# Check Engine light, Rough start, knock



## Bacon21 (Jun 19, 2017)

Hi there. I'm struggling to diagnose my Sentra and what is wrong with it. I'm by no means a nissan fan, but I got both my Nissans for cheap and that's why I have them. Personally I'd rather have a buick, but that's neither here nor there.

So I bought the car (with 170,000 miles) to have something to drive while I put in the time to do some simple repairs on my 99 Maxima. Well 3 days into owning the Sentra, I noticed a slight knock when the engine warmed up. No check engine light or anything, just a slight (yet distinguishable) knock, coming from underneath the car. Welp, that sucks, I've been spending all this time to fix frivolous things on the Maxima I figured I'd let it slide for a while. The knock never went away. As time goes on, I start noticing that the car will idle really rough (for like 10 seconds) and then smooth out for the most part. This was shortly thereafter accompanied by a check engine light. Ran the scanner and the only code I'm getting is Cylinder 3 misfire. I thought "Oh good, just replace the coil pack and we're all good). Replaced the coil pack, aaaand still starts like crap and the check engine light is shining with all of its pride. So I took a stethoscope to the cylinder 3 fuel injector, and its clicking away just the same as the other 3 injectors. So wtf. Another thing to note, my dipstick handle broke off and the stick is stuck deep in the tube. So while I was at work I took some shop air and tried to use the compressed air to blow it out. Instead it blew oil all out from under the valve cover. So I changed the valve cover gasket, and while I was doing that, I noticed that the oil drain hole on the right was completely clogged with sludge (like a perfectly molded ant hill, a big ass ant hill) positioned perfectly circular around and over top the drain hole. How did that happen there and nowhere else?

So from what I've read on the internet, it seems like a bad head gasket could be causing this second issue (I'm already confident I have a bad rod bearing in one of the cylinders, Cylinder 3 maybe????) and am fully intent on replacing it. Question is, is it worth undergoing the work to replace the head gasket and if not what other options do I have to diagnose/solve this mystery?


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