I have a honda civic 98 with a y8 motor and a z6 head. The rattling noise started happening after I fixed the AC. I drove it on the freeway and I had to press the gas hard and it did not want to accelerate with AC on and now I have a rattling noise. I dont know exactly what the noise could be. Could it be the valve train or the pistons perhaps? Here is the video:

 

Acts like it's running on 3 cylinders. Disconnect fuel injectors one at a time while idling to see if there is a dead cylinder.

 

How did you fixed the a/c? If you took something apart, start there. Did you leave any

 

I replaced the AC compressor and the expansion valve with a new one. I will look further and see what I find.

 

I checked each spark plug and they all have spark, I am starting to think its just the motor.

 

My distributor cap is kind of loose, could this have been the cause? I will check tomorrow.

 

Maybe, did you mess with it when you did the installation? I would recheck everything you touched. Maybe there's a tool banging around down there. Double check all the bolts and screws you tighten are tighten. Check the tension in the belt, motor mounts you took off if you had too. Check everything single thing from the time you used the your first tool to the last. How do the a/c feel?

 

Did you replace the belt that drives the A/C compressor? I don't know how the tensioner works for that belt but could be the belt slightly mis-aligned or mis-tensioned and hitting something you can't see.

 

The AC is not that cold, I am thinking it could be the drier yhats causing these problems?

 

The drier is a passive part- there are no moving parts in it or attached to it. It could cause a/c to not be as cold as it should be but It seems like the drier would be unrelated to your rattling noise. Did you check the belt like I suggested?

 

This looks like the result of a poorly put together mini me. Plus it's never good to use the z6 head on a y8 block, timing can be close with a aftermarket cam gear but never correct. Timing was probably never set even close to spec and bent a valve, soon it will drop and seize the motor.

 

I think you are right, timing was set but it might now have not been exact exact timing. And I am convinced the motor's crankshaft bearing is what I am hearing. I found a really cheap y7 engine, might as well just downgrade and sell it. Also, I have noticed the engine accelerates by itself in the freeway but only with the AC on. I forgot to mention that it does have an error code for the knock sensor. I had just found out that this knock sensor is not OEM, and that is why I am getting the code. I didnt think the knock sensor would be so important.