I just purchased a J30 with intentions to fix it and sell it. Something is wrong with the motor, or maybe...a few things. It starts fine but runs pretty rough and has an assortment of noises. Both of these noises increase with RPM. One of them is a scratching which sounds like its coming from the timing case and then there is a ticking which I have yet to pinpoint the location of.

I have a 95 Maxima with a VQ35 so I know my way around some of this Nissan stuff a little but am not familiar with the VG motor itself and I know they all have their quirks. I pulled the plugs on each coil pack to detect a difference in the motor and it SEEMED as if the two rear most cylinders on each bank did not create a difference with the coil packs unplugged. I could be wrong however but the previous owner said something about a "piston being bad" so who knows what the mechanic actually told him.

I'd like to hear that these are things easily fixed without completely disassembling the motor and taking anything to a machine shop. Worst case scenario- I will source a new motor and swap it but that is going to really strain the budget.

The car only has 105000 miles on it...I guess they just didnt take very good care of it. Anyway, enough talk, here is the video. I appreciate any help.

http://www.youtube.com/watch?v=ER1O-HNfe4w
[youtube]ER1O-HNfe4w[/youtube]

 

my car has been making a similar timing cover noise i narrowed it down to the upper idler my advice take a long screwdriver/extenion/crowbar etc stick it down by the plenum right behind where the upper idler would be(top over cover smack dab in the middle) and listen if the noise coming from the tool is really loud its the idler

 

check the compression if someone has told you it's a bad piston. it's pretty clear whether pulling the rear coil packs makes a difference or not, so check that again.

all that said, it sounds like you are not firing on all the cylinders and that squeeking is possibly an idler pulley. try running the car without any drive belts if you want to narrow it down. some tests like those will tell you whether you will need to go into/replace the engine.

 

thanks guys. I was thinking the same thing- it doesnt seem like all cylinders are firing. It idles so rough already its only slightly noticeable when the coilpack is unplugged but I definitely could tell on the four front-most cylinders.

I guess my biggest fear is that it would be a bad rod bearing. I'm going to check that idler pulley and buy a compression tester. I'll be back with what I find later.

 

Okay I'm happy to report that the compression in all cylinders seems to be good. They read like this.
cyl 1:180
cyl 2:170
cyl 3:180
cyl 4:170
cyl 5:175
cyl 6:170

No big variations and they seem to be almost perfectly in spec. I just read in the FSM however that they suggest disconnecting the cam sensor and pressing the gas pedal down all the way during cranking. I didnt do either of these things and I forgot to depressurize the fuel system as well. I dont know if this effects the readings or its more so you dont flood the motor. I also wanted to mention that it looked like gas was spraying out of the spark plug hole on cylinder 5 when I was cranking. I didnt notice that from any other cylinder.

I tried flipping coils between the front and rear cylinders to see if that is causing any problems and didnt really notice any difference. Something is going on with cylinders 5 and 6. The spark plugs looked about normal with maybe a little darker color to 5 and 6. I think maybe the distributor coil/ignition control piece that sits on the rear of the manifold is from a junkyard due to the white-out looking marking on it someone correct me if that is something OEM, I also noticed it on a fuel-line.

I'm going to try to check if there is spark getting to the rear spark plugs. Otherwise my next guess might be injectors or something electronic?? All the noises except the screeching idler pulley seem to have disappeared.