L89 Engine knock/ping
Thread Starter
Melting Slicks
Joined: Apr 2004
Posts: 2,099
Likes: 0
From: Springfield PRoP
Cruise-In VI Veteran
L89 Engine knock/ping
Howdy all. I have a 88 auto with 175k miles on it. last week, 2 days after I filled the tank, my Vette developed a knock/ping. I have checked the oil level, it is fine, oil pressure is good as well. I also noticed earlier in the summer it seemed to be running a bit rich, and the idle doesnt want to drop down when I first stop. The knock doesnt seem to be RPM dependent, but more throttle position dependent. By that I mean, the knock seems to get worse the more gas I give it, but once I am at a certain speed, and back off the gas, the knock goes away. Also, if I pull it down manually, and the RPMs go up, the knock doesnt come until I give it gas.
It sounds like something hitting a metal fan blade, kinda loud, but "sharp and tinny".
So, I am pretty sure it isnt a rod knock, my guess anyway. could it be the injectors going? I have heard they can make a god awful noise when they go, or is it something else? And yes I have more gas in, and ran some Octane booster thru it with no improvement.
Thanks all
lol, just realized it mixed up the freaking numbers on my engine in the post title. Doh!
It sounds like something hitting a metal fan blade, kinda loud, but "sharp and tinny".
So, I am pretty sure it isnt a rod knock, my guess anyway. could it be the injectors going? I have heard they can make a god awful noise when they go, or is it something else? And yes I have more gas in, and ran some Octane booster thru it with no improvement.
Thanks all
lol, just realized it mixed up the freaking numbers on my engine in the post title. Doh!
Last edited by biglou71; Sep 21, 2008 at 10:30 PM.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Check to see if you have any knock sensor codes.
I don't think running rich would cause a knock or ping, though running lean might.
Since it's acceleration dependant it seems to depend upon cylinder pressure. Could that not represent a rod or bearing issue??
Have you pulled the spark plugs to see if they show anything unusual?
I don't think running rich would cause a knock or ping, though running lean might.
Since it's acceleration dependant it seems to depend upon cylinder pressure. Could that not represent a rod or bearing issue??
Have you pulled the spark plugs to see if they show anything unusual?
Instructor
Joined: Jun 2008
Posts: 138
Likes: 0
From: Bridgewater Ma.
Lou, first start off with checking the basics.
You said you just filled up the fuel tank. Have you experienced heavy rains recently in your area? I would eliminate fuel contamination, add some fuel treatment.
Is your engine running hotter than usuall?
Check your fuel pressure. What is the reading?
Check your static timing.
Do you still run the original Multec injectors? Have you ohmed them hot and cold?
Check the proper operation of your EGR valve.
You said you just filled up the fuel tank. Have you experienced heavy rains recently in your area? I would eliminate fuel contamination, add some fuel treatment.
Is your engine running hotter than usuall?
Check your fuel pressure. What is the reading?
Check your static timing.
Do you still run the original Multec injectors? Have you ohmed them hot and cold?
Check the proper operation of your EGR valve.
Melting Slicks
Joined: May 2007
Posts: 2,171
Likes: 1
From: Warwick RI
Howdy all. I have a 88 auto with 175k miles on it. last week, 2 days after I filled the tank, my Vette developed a knock/ping. I have checked the oil level, it is fine, oil pressure is good as well. I also noticed earlier in the summer it seemed to be running a bit rich, and the idle doesnt want to drop down when I first stop. The knock doesnt seem to be RPM dependent, but more throttle position dependent. By that I mean, the knock seems to get worse the more gas I give it, but once I am at a certain speed, and back off the gas, the knock goes away. Also, if I pull it down manually, and the RPMs go up, the knock doesnt come until I give it gas.
It sounds like something hitting a metal fan blade, kinda loud, but "sharp and tinny".
So, I am pretty sure it isnt a rod knock, my guess anyway. could it be the injectors going? I have heard they can make a god awful noise when they go, or is it something else? And yes I have more gas in, and ran some Octane booster thru it with no improvement.
Thanks all
lol, just realized it mixed up the freaking numbers on my engine in the post title. Doh!
It sounds like something hitting a metal fan blade, kinda loud, but "sharp and tinny".
So, I am pretty sure it isnt a rod knock, my guess anyway. could it be the injectors going? I have heard they can make a god awful noise when they go, or is it something else? And yes I have more gas in, and ran some Octane booster thru it with no improvement.
Thanks all
lol, just realized it mixed up the freaking numbers on my engine in the post title. Doh!
Safety Car
Joined: Sep 2001
Posts: 4,150
Likes: 552
From: Glenbeulah Wi
Make sure the knock sensor is working, can you scan the car and see if you are getting knock signals from the knock sensor? The knock sensor or circuit may have failed.
Other causes as prevoiusly mentioned:
-EGR failure
-Exhaust leak
-Excessive timing
-Poor gas
-Vacuum leak
-Bad injectors
Other causes as prevoiusly mentioned:
-EGR failure
-Exhaust leak
-Excessive timing
-Poor gas
-Vacuum leak
-Bad injectors
Thread Starter
Melting Slicks
Joined: Apr 2004
Posts: 2,099
Likes: 0
From: Springfield PRoP
Cruise-In VI Veteran
She has had a small exhaust leak for a bit, never even considered that could be what the issue is, ie it has got worse.
I will check that out. hmmmm nice way to tell the wife I need new headers......
Melting Slicks
Joined: May 2007
Posts: 2,171
Likes: 1
From: Warwick RI
I would say that it is a definate "while I'm there" item
If it turns out to be the cause that is
