Stumped on knock noise

Without being there in person, and we all know internet troubleshooting isn't worth a dang, I'm leaning toward vacuum leak. Then fuel system/delivery.

Worn bearings are not at the top of my list. If you really think it's a bearing issue, then throw some 20w-50 in it and see what happens.

 

Here's a bit of info....

RANDOM MISFIRES

After reading that, I am leaning even more toward a vacuum leak.

If the bottom end is shot, thicker oil isn't going to hurt it any............but it should make it less noisy.

I don't think it would cause any problems, even if the engine were new. It would drop your mpg a little, but I don't think the 1.5L engine is full of tight clearances that would starve due to thicker oil, especially at 300k miles of wear.

Many times it's the most simple answers that solve our problems. Replacing an engine doesn't fall under that category right now.

 

Starting fluid to look for a vacuum leak? Wouldn’t a spray bottle of water be a little safer?

 

In the old days of carbs and non-electronic idle control, starting fluid would cause the engine rpm to jump rapidly if sprayed near a vacuum leak. Made it easier to ID the location. I haven't had to do this in a long time, so I personally don't know if it's still as effective for a modern engine. I'm sure it would make some difference in the engine sound.

 

Have you checked the COPs (Coil Over Plugs) to ensure they aren’t an issue and the spark plugs have good contact?

 

OEM?

 

Mine is an Australian build so has a fuel filter and that turned out to be the problem. I believe the US versions do not have an external fuel filter and everything is in the tank. Does the US model have a fuel supply and fuel return line? If so, disconnect the return line and put it into a suitable container. This is to see how much fuel is going back to the tank. Add a T piece and pressure gauge and slowly clamp off the return line while watching the pressure and fuel flow. You should see at least 40psi and still have good fuel flow through the return hose.

T1 Terry

 

No, the fuel return line was eliminated, hence one less source of hydrocarbon emissions.

I agree that fuel line pressure should be checked, and the spec is 44 to 50 psi at idle.

It is possible that a vacuum leak would allow excess air to enter the intake manifold and cause engine misfire; however I would then expect DTC P0171 (system too lean) to be logged by the engine ECU.

OP says that the engine compression was checked. What was the method to check the compression, and what were the results? Since he does not have access to Techstream my guess is that MG1 spun the engine at the typical 1,100 RPM. That will make cylinder compression look pretty good compared to a test on a regular vehicle where the starter is spinning the engine at around 300 RPM.

While using Techstream, the spec is 128 psi, 99 psi minimum, difference between cylinders should not exceed 14 psi.

There is no problem with the use of 20W-50 except that in the winter months, the engine may have some difficulty starting due to the thick viscosity vs. 5W-30 oil.