Engine knocking and low oil pressure
Thread Starter
Melting Slicks
Joined: Oct 1999
Posts: 2,501
Likes: 177
From: Houston, Texas FEAR THE BONES
2023 C5 of the Year Finalist - Modified
Engine knocking and low oil pressure
Just recently started doing this. Always around 2,000 RPM, only when load is applied (won't knock in neutral). It is a rattling, knocking sound that is very annoying and probably not good for the engine, but I have no idea where to begin to look :confused: . The engine still revs ok, and it makes no unusual noises below or above 2,000 RPM. Maybe a loose rocker? Also seem to have low oil pressure at idle and low RPM, around the first hash mark on the dash guage. Don't know if this is a related problem or a whole separate issue. Anyway, if anybody has any ideas on where to look, I'd be interested in hearing them. Thanks! BTW, I just changed plugs and wires, and had a new opti and water pump @ 50,000 miles.
Race Director
Joined: Mar 2001
Posts: 14,480
Likes: 132
From: PA
Re: Engine knocking and low oil pressure (94vette)
Maybe an oil change will help? How old is the oil thats in your car? My Dads Jeep did the same thing you're describing so I changed his oil and it went away. I'm guessing there was a hunk of dirt stuck in the oil pump and the change cleaned it out.
Thread Starter
Melting Slicks
Joined: Oct 1999
Posts: 2,501
Likes: 177
From: Houston, Texas FEAR THE BONES
2023 C5 of the Year Finalist - Modified
Re: Engine knocking and low oil pressure (Nat96LT4)
Actually, the oil is kinda old, so I'll do an oil change and see if makes any difference. Thanks. Anyone else have any comments??
Safety Car
Joined: Mar 2000
Posts: 4,847
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From: Bartlett, IL
Cruise-In XI Veteran
St. Jude Donor '06-'07-'08-'09-'10-'11-'12
Re: Engine knocking and low oil pressure (94vette)
If it is only at 2000 rpm I doubt that its a rod knock. A rod knock would get louder as RPM increased, could it be some kind of vibration, is it a rattle or a knock?
Safety Car
Joined: Mar 2000
Posts: 4,847
Likes: 10
From: Bartlett, IL
Cruise-In XI Veteran
St. Jude Donor '06-'07-'08-'09-'10-'11-'12
Re: Engine knocking and low oil pressure (MVR 155)
One last thing, what kind of gas are you running in the car?? Could it be fuel pinging, Try filling up from a different gas station than you normally go to and put a tank of premium in and see if it goes away.
Thread Starter
Melting Slicks
Joined: Oct 1999
Posts: 2,501
Likes: 177
From: Houston, Texas FEAR THE BONES
2023 C5 of the Year Finalist - Modified
Re: Engine knocking and low oil pressure (MVR 155)
MVR,
It sounds like bad knock like you get from bad gas; however, I filled up at least 3 different brands of gas stations with no difference. I only run 92-93 octane gas, so I don't think this is the case. Also seems to be much louder and worse with the A/C on (it will knock at 1500 RPM through 2500 RPM with the A/C on). I had the fuel filter changed at around 45,000 miles; I am now at 80,000 miles. I wonder if I need a new filter?
It sounds like bad knock like you get from bad gas; however, I filled up at least 3 different brands of gas stations with no difference. I only run 92-93 octane gas, so I don't think this is the case. Also seems to be much louder and worse with the A/C on (it will knock at 1500 RPM through 2500 RPM with the A/C on). I had the fuel filter changed at around 45,000 miles; I am now at 80,000 miles. I wonder if I need a new filter?
Safety Car
Joined: Mar 2000
Posts: 4,847
Likes: 10
From: Bartlett, IL
Cruise-In XI Veteran
St. Jude Donor '06-'07-'08-'09-'10-'11-'12
Re: Engine knocking and low oil pressure (94vette)
Your AC compressor could be the problem, take the Serpentine belt off of the car and run it for a few seconds, see if the problem is still there, if it goes away you know the problem lies in one of your belt driven accesories.
Racer
Joined: Oct 2000
Posts: 460
Likes: 0
From: Lincoln NE
Re: Engine knocking and low oil pressure (94vette)
Hate to be an alarmist and will probably be flamed, but I wouldn't rule out a spun rod bearing. This is what mine did with that problem,
Low oil pressure at idle, 0 to 5 psi, that increased to like 24-25 psi at cruise.
Knocking sound when pulling away from a stop sign or whenever the engine was under a heavy load at lower rpm (2000 RPM and below).
One way to diagnose the problem. When you have the oil changed, have the old filter cut open and inspect it for metal particles. If there is metal in the filter, then you got a real problem.
Low oil pressure at idle, 0 to 5 psi, that increased to like 24-25 psi at cruise.
Knocking sound when pulling away from a stop sign or whenever the engine was under a heavy load at lower rpm (2000 RPM and below).
One way to diagnose the problem. When you have the oil changed, have the old filter cut open and inspect it for metal particles. If there is metal in the filter, then you got a real problem.
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