I have a problem with my '89 Buick Century with a 2.5 four cylinder engine. This is the famous "U" block. About 8 months ago, the car started making a vibration sound, which really sounded like it was coming from the dash. The car is getting old, so I didn't think much of it. The vibration would start and stop at any time. Well today, I took the car on the interstate, and the vibration got REALLY LOUD. Again intermitant, would vibrate loudly then stop, the start again then stop. Pulled the car over, checked the oil. Oil dirty with 4,000 miles since last change, but full. Vibration start and stop at idle, with acceleration and at highway speeds. Car seemed to have full power with the motor, no missing or poor idle. So, I was thinking that I had a bearing going out on the AC compressor or the tensioner. Oil was full and it had normal power in the motor, I decided to drive it home. On the way, at 75 mph, the oil light came on the the motor died. Car will restart, idle, and drive, with loud vibration noise but the oil light stays on. Also pulled the dipstick, oil again still full but smelled faintly 'burnt'. No loss of oil either. Where do I start trouble shooting this problem? Any ideas on what the problem could be? By the way, car only has 92,000 miles and has been taken care of, not hot rodded. Thanks in advance. Clove
If you have a throttle body, check all the sensor wires to it. My Blazer was doing a similar accelaration /power knock and my mechanic found a loose wire in the throttle body that was throwing it off like if a 4 barrel carburator didnt kick in the 2nd set of barrels. When I got it to him it was barely creeping and smoking like a Kenworth on a steep grade and the engine was a crated rebuild with less than 1000 miles. A new connector on the throttle body sensor wire, set of plugs to replace the fouled ones and I was good to go.
I have an 86 Toyota that was doing the exact same thing. No way of telling when it would start, but it did get really loud. Pretty scary, huh? Sounds like the car is about to fall apart. However, a tiny piece of gravel in the hubcap can make a car sound like it needs a front end rebuild and I bet the same thing is going on here, especially since it sounds like it's in the dash. Mine turned out to be something wedged in the air intake system. A dry leaf or a scrap of paper or plastic. As you're driving, switch around the defrost/foot/ac/whatever the other options are and the speed of the fan, all that stuff. If the problem is the same, you'll probably hear the noise and/or encounter some resistance on one of the settings. Take the car out somewhere where you can drive fast, mess with the settings, turn on the fan full blast, and whatever is in there should get blown out. Or of course you could hunt around in there and find the tattered scrap of whatever it is lodged in the system. It does heat up the engine, hence the oil light. Worth a try anyway before paying for a new engine. Good luck.
There's a possibility your oil pump pick up tube may be clogging up and starving the engine of oil. The longer you drive the more it picks up sludge from the bottom of the pan, when you shut it off the sludge settles back to the bottom. After a period of time the screen remains clogged. The vibration you were hearing may have been a valve tapping as they are the last thing in the system to get oiled. The timing gears also are notorius for making noise, will make the engine sound like a diesel, probably not your problem though. First thing I'd do is hook an oil pressure gauge to it and see what for pressure it has, but if the engine bearings are knocking don't waste to much time on it cuz it probably needs a motor. Finding a good used motor will be your cheapest way of repair. Good Luck..
Remove the oil filter and then cut the canister open and see if there are metal fragments in the filter media. If there are then you are sol. If the filter media is clean other than being black proceed with verifying where the fault lies. Good Luck
Let me see if I understand this correctly. You have ignored a vibration for eight months until it got REALLY bad today, then you proceed to drive this 4 cylinder home at 75 mph? Is that correct? Well, since you did make it home, and since the vibration is at idle or at highway speed, I'd check the fan clutch/bearings. What I wouldn't do is continue to drive the vehicle for any distance above a slow crawl. But of course I'm not brave enough to drive a vehicle with a bad vibration at 75 mph either.
Thank you for all of your responses. I had a mechanic listen to the engine today. We both agree that the problem is not a broken piston, crank, cam, lifter or valve or bearing. The noise definately does not sound deep in the motor, but the oil light stays on when you start it. Irrepairable internal damage may have already occurred, however. By the way, this vibration for the past 8 months has just sounded like a hum. I know that saying that I ignored the hum/vibration sounds really bad to any reader of this post, but the hum/vibration did not sound like anything bad. I truly believed the noise to come from the dash, possibly a blower motor. The noise was also intermittant, sounding very loud at times and not at all other times. The reason I kept driving the car yesterday was because the oil resevior was full and the loud vibration still did not appear to be coming from the motor itself. Maybe the compressor or the water pump, but not the motor. I will pull the filter and drain the oil to check for metal shavings. If I don't find any shavings, I will drop the oil pan soon to see if I can get the the internal oil pump. I am leaning towards this as the problem. Shrek, I did just replace the injector in the throttle body. I am perplexed though...how could this be the problem? The car ran at idle and at highway speeds with full power and no problems. The car does not smoke or run rough. How would it cause there to be no oil pressure? Thank you again. clove
Clovis, regarding the oil filter.....I am suggesting that you cut the can open and to look at the pleated filter material to search for metal fragments. I was unsure if I was clear on that.
Yes, I will take a good look at the filter. It actually has a filter that fits into the bottom of the oil pan, and does not have a metal cover on the outside of the filter. What will the metal flakes look like, by the way???? Slivers or specs? Shiny or dull? Thanks! clove
My guess would be the harmonic balancer has been coming apart for quite some time, causing the motor to vibrate at odd intervals. It's now finally disintegrated totally. This will literally throw off everything, causing the engine to fail to idle AND cause fast and excessive wear in the front main bearings and possibly the forward rod bearings as well. You might get lucky, if the balancer is indeed bad, and simply putting another on will cure the problem. The oil light makes me wonder though. Does it stay on when you take the engine above idle? If not then it's probably just idling too low to carry sufficient pressure. If it stays on at all RPM you are, probably, toast. Nice thing is you can get good 2.5's from most boneyards for about $250.00 and they are easy to install. (Thinks carefully about engine sizes...the 2.5 is the standard Chevy motor and not the Quad Four, correct? If so then they are cheap...if it's a Quad then all I can say is call the boneyard.)
Without the proper sensor signal at the throttlebody controlling the accelleration jets the engine fluctuates jet configuration resulting at first in a little ping/knock on hills etc. It wont start smoking until that sensor is badly nonfunctional.
does the fuel pump mount to the side of the motor ? If it does check the oil to make sure it is not getting gas in it had this to happen to a ford product best advise if your vechile doesn't have an oil pressure gage put one on it it only takes 6 psi to make the light go off.
Clovis, my husband recently rebuilt the 2.5 engine in an '89 Cutlass Calais for our daughter to drive to college. The harmonic balancer needed replacing, which meant replacing the whole crankshaft. Dealer cost was $500, parts place $250. The car ran like new until her EX-boyfriend(notice the emphasis on ex) got ahold of it. Now it's sitting back in the driveway needing the whole engine replaced. :waa: When my dh dropped the oilpan, parts of the bearings and bottom of the #2 piston were in the oilpan. The oil had a metallic sheen when rubbed on our fingers. That look to the oil is what you need to look for when you pull the oil filter. Susan
