Rattling noise upon coming to Idle

[orange57]

Its an 89 olds 98, 211K on the clock. If you blip the throttle and let it come back to idle there is a rattling noise, sounds like its coming from the intake manifold area. Also I can notice it when coming to a stop. If you hold the throttle open some you can't really hear it. And it isn't constant, it will come and go. Any ideas? I'm wondering if I have a stuck lifter or???? If it's the motor going, then it might be time to let the car go.

Thanks,

matt

[MagicRat]

Have you ever changed the timing chain?
If not, given the mileage, it's probably really loose. Sometimes the slack side of the chain likes to flap around and hit the housing.

Changing the timing chain is not particularly difficult. If the rest of the car is pretty good, it's probably worthwhile to do.

But if you are, don't delay. You would not want the loose chain to skip a tooth or to erode the timing chain cover.

[orange57]

I have replaced the timing chain before, i want to say around 150Kish, don't really remember, may have been less miles. It doesn't sound like it's coming from the timing chain area though. More around the intake, or possibly the rear valve cover. I need to replace the rear valve cover and will take a look to see if anything looks out of wack. Any other suggestions?

Thanks,

matt

[MagicRat]

Next suggestion.... my '88 Bonneville (same engine and chassis) had a similar rattle coming from a loose heat shield on the catalytic converter, which is just a couple of feet below the rear valve cover. Even though the shield did not appear to be loose, it was just bad enough to resonate at certain rpm's.

I wrapped a big, stainless steel hose clamp around it, which made it quiet.

[orange57]

Originally Posted by MagicRat

Next suggestion.... my '88 Bonneville (same engine and chassis) had a similar rattle coming from a loose heat shield on the catalytic converter, which is just a couple of feet below the rear valve cover. Even though the shield did not appear to be loose, it was just bad enough to resonate at certain rpm's.

I wrapped a big, stainless steel hose clamp around it, which made it quiet.

That might just be it. I will get the car up on ramps this weekend and see if that does it. I noticed when I stuck my head under the front bumper it sounded pretty loud down there too. My fingers are crossed because if that was it I would be pumped. I put a hell of a lot of effort to put a new tranmission in it and it would suck if the motor went right now. I will keep you posted on what i find.

thanks,

matt

[orange57]

Ok, well it isn't a heat sheild on the catalytic converter. I took a look at it this weekend and i don't think it has the same sheild. Another thing i noticed is if it is rattling and I put it into gear it seems to go away. I'm hoping it isn't the trans, cause that is a PITA to replace and I don't want to do it again. But, i guess it will be what it is. Any more thoughts?

Thanks guys.

matt

[orange57]

Would it be a bad thing to unbolt the torque converter from the fly wheel and start the car to determine if the rattling is coming from the trans or the engine?

[HotZ28]

Its an 89 olds 98, 211K on the clock. If you blip the throttle and let it come back to idle there is a rattling noise, sounds like its coming from the intake manifold area. Also I can notice it when coming to a stop.

Sounds like the typical symptoms of a failed harmonic balancer, The outer ring will separate from the inner ring due to age. Check by putting your hands on the outer ring (engine off, of course) and see if you have any back & forth movement.