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Doug
Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 6924
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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I have a knocking super fast near cylinder 1. I took scope

Customer Question

I have a knocking super fast near cylinder 1. I took scope to it and sound like intake and water pump area. Adjusted the lash and still there. Replaced the water pump and still there! What else can I try before pulling the head? How to check springs? No idea what it could be! Help!!!
Submitted: 1 year ago.
Category: Mitsubishi
Expert:  Doug replied 1 year ago.

Hi,

What model vehicle is this?

Customer: replied 1 year ago.
Lancer ralliart 2.4l the 4g69 motor
Expert:  Doug replied 1 year ago.

Thanks.

Please unplug the #1 fuel injector and see if the knocking stops or quiets substantially. Note the engine will run poorly of course, we are just interested in seeing if it changes the intensity of the knock.

Customer: replied 1 year ago.
Ok it is already running poorly. I won't be near the vehicle till 1 hour from now
Customer: replied 1 year ago.
Also it is throwing no codes
Expert:  Doug replied 1 year ago.

No problem, we can pick up later.

The purpose of this test is to see if the noise is coming from the bottom end... when the fuel is cut there will no longer be any combustion, and if the noise is in the bottom end it will quiet down. We can repeat on the other 3 cylinders, but it sounds like you already have narrowed it down to the front of the engine.

If there is no change at all, we will next want to remove the front timing covers and check the timing belt tensioner condition as they have been known to knock real badly if they fail.

Customer: replied 1 year ago.
I have already replaced the tensioner since I did not have the tool to compress it when I swapped the water pump
Expert:  Doug replied 1 year ago.

Thanks, ***** ***** rules that out most likely anyway. We will still want to check the adjustment of the mechanical tensioner too though; if it was installed incorrectly it will cause the same sort of noise as the tensioner extends.

Customer: replied 1 year ago.
It is not coming from the timing area at all. More towards the intake manifold top by cyl 1. I will try fuel injectors. Sounds like rocker or lifter type noise just really loud!
Expert:  Doug replied 1 year ago.

Just to be clear, when you are saying cylinder #1, you do mean the one nearest the timing belt right?

Customer: replied 1 year ago.
Customer: replied 1 year ago.
I meant it's not coming from the side portion of the engine. Ie vertical side. From top back area where the intake manifold connects
Expert:  Doug replied 1 year ago.

Okay, just making sure we are on the same page.

Lets do the injector unplugging tests and see if the noise quiets any, which again would indicate a problem primarily in the bottom end. If it does not change at all and you know your valves are adjusted properly, then we will still want to inspect that tensioner adjustment next.

Expert:  Doug replied 1 year ago.

With it sounding like the intake and water pump area, I have a feeling we will be dealing with a bottom end knock and it will likely get quieter when you unhook power to the affected cylinders' injector. Lets check it out first though and see if we are on the right track.

Customer: replied 1 year ago.
Headed to car now. Will get back when I pull injector
Customer: replied 1 year ago.
Is there a way to send you a video of the noise?
Expert:  Doug replied 1 year ago.

Yes, the easiest way would be to upload to youtube and then post a link here.

Customer: replied 1 year ago.
Unplugged all of them one at a time. No change
Customer: replied 1 year ago.
I also have a video scope of that helps. Setting up YouTube now
Customer: replied 1 year ago.
https://youtu.be/Jp-nveAqnUo Here is the link
Expert:  Doug replied 1 year ago.

Yeah that isn't at all what I was expecting. That just sounds like valve train noise, a hair louder than usual but nothing really drastic.

When you adjusted the valves, did you do so hot or cold? What did you adjust them to?

Customer: replied 1 year ago.
We did both actually. And the second time it seemed to have been looser than we set it the first time. I believe it was .008 and .012
Expert:  Doug replied 1 year ago.

Thanks.

Those are the right numbers... making sure of course you are using inches and not mm and the .008 is intake and the .012 is exhaust.

However you must do these with the engine completely hot or they won't be any good.

Lets run the engine up to full operating temperature and check your clearances again and see where you stand.

I'm attaching a chart to help with identifying which valves can be adjusted when; the white arrows are for when the engine is at TDC (mark on cam at 12 oclock) the black arrows are for BDC (mark at 6 oclock).

Customer: replied 1 year ago.
I already did that. Today we did it a second time. I have the technicians chilton for it here. When this started I was accelerating to get on the freeway when it started to bog down then the noise started getting gradually louder and car was sputtering. One of the plugs had the center ceramic broke and wiggling around and I believe cyl 3 had oil on spark end of plug
Customer: replied 1 year ago.
Should I scope the cylinders through plug holes with my camera?
Expert:  Doug replied 1 year ago.

Well that would certainly be really useful information!

Yes, lets take a look down into the cylinder that had the plug failure. If we lost any part of that plug down there we've got issues.

Customer: replied 1 year ago.
Not sure which one it was but I'll check them all. What are big red flags for anything else I find in there
Customer: replied 1 year ago.
Also a few days before the MAF sensor said was too lean.
Expert:  Doug replied 1 year ago.

Check for debris first and foremost, but also look for signs of damage from foreign matter being in there previously as well.... any marks at all on the cylinder walls primarily, but the face of the piston and if you have a reverse head camera end the combustion chamber as well.

Customer: replied 1 year ago.
Don't see anything inside. Cylinder 4 is super clean piston cyl 1 very dirty. It's carbon
Customer: replied 1 year ago.
Cylinder walls look clean too
Expert:  Doug replied 1 year ago.

Hmm.
Unfortunately at this point I think you are probably going to need to pull that head for inspection.
I don't really see any other real expectations... the sound sounds like the valves are out of adjustment, but you are certain they are fine. That does leave debris in the cylinder as a suspect as it sounds the same, but nothing is found there even though we know we had a plug fail.

Customer: replied 1 year ago.
Well the plug piece wasn't missing just loose. Is there suppose to be sideways play on the rocker assembly?
Expert:  Doug replied 1 year ago.

A little yes.... do you have excessive play? Like it moves all the way to the advanced position for mivec?

Customer: replied 1 year ago.
Cylinder 3's plug end is soaked in fuel
Customer: replied 1 year ago.
Are there any vacuum tests I can do?
Expert:  Doug replied 1 year ago.

Not really.... you either have engine vacuum or you do not. You should have 15-17inHg at idle (varied 15% or so depending on altitude), if you do not then there is a problem with your valves (be it mechanical problem, timing problem, etc).
If #3 is soaked in fuel, are you certain you have spark there and are certain you have good compression there?

Customer: replied 1 year ago.
It was 200 and new plug
Expert:  Doug replied 1 year ago.

Are you certain you have spark there, regardless of the newness of the plug?