Hey blades, I've been trying to track down the cause of engine knock in my car for the past few months. It's pretty minor, but I know that it's a destructive process that, over time, can ruin an engine. So, I'll start with my car. It's a 1997 Buick LeSabre Limited with a 3800 Series II under the hood. It only has 117k miles on it, which isn't all that much for a car of it's age. A few months ago, I noticed a bit of engine knock, pinging, detonation, whatever you want to call it. It was pretty minor, and I switched from 87 octane to 93. That solved the problem for the time being. The knocking started again about a month ago. Again, it's pretty minor, only when the throttle is more than halfway pressed. I've brought it to my mechanic, and he said he can't find anything wrong with it, and there are no error codes. He cleaned the valves for me, and put injector cleaner into my tank. I've burned through that whole tank, and still the problem is there. A while ago I noticed a pretty large crack in the intake hose, after the MAF. I taped it up pretty well, but I haven't gotten around to getting a new one yet. Could this be the problem? I mean, if the engine is sucking in air after the MAF, and it thinks it's getting less air than it really is, then wouldn't the engine be getting an improper amount of gas? This problem is irritating, any suggestions on what to do? I have limited knowledge and no experience, but if the fix is simple I can do it myself. Worse comes to worse, I can buy a new engine. 3800's are cheap as hell. Edit: Car still has full power, and my mechanic said the knock sensor is functioning.
If its after the MAF it can cause lean issues that could cause knock, but if you were running lean I would expect the 02 sensor to catch this and compensate. But if the crack was large enough, the computer may not be able to dump enough fuel to compensate. Have you checked the 02 sensor as well? It could be on the way out.. Sounds like you have some more problems than just the cracked intake. Could be Wrong though
Could be a carbon build up in the combustion chambers. Wrong air fuel mix could be the cause. Take it to a parts store and get them to check for codes...good luck...also go to forums about your car and see if there is any info about this problem....
I'm pretty sure that the 02 sensor has been checked, but I will double-check it. I have noticed slightly (1-2 mpg) decreased gas mileage. I'll see if I can get my hands on an OBDII code checker.
You could also pull your plugs and check the condition of them, look at the gaps and for excess carbon....
You possibly have a miss in a cylinder causing it to make a knock sound as the crankshaft rotates around everytime.
Nah, it's NA. I had my knock sensor checked, my mechanic said it's functioning fully. I did put a lot more duct tape over the intake hose today, and it seems to have reduced the knock slightly. I'm getting a new hose this week, so if the problem persists I'll update this thread. Edit: I'll see if I can check the timing. Found this in an article, it describes the problem I'm having. The speed of the knock increases as RPM increases, and gets louder under load too. Fixing something like that will be a bitch.
You would have to drive the piss out of the car and skip oil changes for that to be happening this early in its life. I wish you had diagnostic software to see if the Ecu is retarding the timing.. It would tell you whether it's a mechanical or a/f problem right away. -any actual knock or detonation is going to increase with rpm and load -there is no fixing rod knock. It means a new engine. You could rebuild it but it'll cost less to buy a used engine
New motor time, I thought you were describing ignition knock....Check out LKQ auto parts they are all over the US and they sell guaranteed engines as well as other salvage parts at good prices....google LKQ and you can get prices from their website...good luck...
As much as I didn't want to hear that, I think you guys might be right. If I get a new motor, I'm going the supercharged route. This car will be a hell of a lot more fun with 60 more horses. I'm going to drive this engine until it stops, though. Thanks for the help, guys. It also doesn't help that my mom is taking the car to move my sister into school tomorrow, which is a good 100 miles away. She thinks that it's just an "old car noise" and that it will be fine. Ugh.
Honestly i'd tell your mom to find a different car, depending how bad it is that engine could fail at any time. Sucks to hear about the knock, i've been through that a couple times myself.
I would like to, but she paid for the car and it's ultimately not my place to tell her no. I told her that there is a chance she could get stranded, and she pretty much got mad at me and keeps telling me it's the "lifters."
Hey if shes gonna argue with you w/e. You just get to rub it in her face if it does break down lol. An RPM related noise issue could be valvetrain noise as well. Best bet is get a long screwdrive and put the handle end up to your ear and the tip on the lower engine block, and on the heads. With the engine running listen to it, if the sound is louder in the block its prolly rod knock, if its louder in a head, its prolly valve issue.
I'll give that a shot, the knock is just about impossible to hear at idle, but maybe i can pinpoint where it's coming from. If it's preignition, would i hear it most from the head or the block? I just hope it's not a bearing. It doesn't sound so much like knock, it's more of a quiet clicking or ticking noise.
Update. I listened to the car, and the noise is barely audible at idle. Its coming from the top of the engine, so i know its not a rod bearing. I can hear it most from the valve cover over a specific cylinder. I suspect it might be the lifter. If i unplug that cylinders spark plug while the engine is running, and the noise stops, then that should help me diagnose it. I'm going to take a look at the lifters soon, how can i visually tell if that is the problem?
Ok. I counted how many times i hear the tick per second, and i got 8. 8 x 60 seconds is 480, about half my idle speed so I'm sure its not a rod bearing now. I picked up some seafoam, when i replace the intake hose this weekend I'll run that through and see if that will help. If it doesn't, I'm just going to go ahead and replace all the lifters while i have the engine open.