Raspy engine noise

[KevAndAndi]

I have found various threads on this topic, but I thought I would post my own, as it seems there is sufficient variability of causes for this issue.

The problem is a raspy engine noise that manifests itself at about 2k to 3k RPMs. It sounds a bit like what would happen if you left a pie tin on top of the cam covers. At a certain frequency, the pie tin would sympathetically vibrate and clatter against the covers.

From reading other threads, I realize I have to check for loose connectors, check my valve clearances, and check the exhaust manifold connectors and gasket. However, I have a feeling the issue is related to the #1 cylinder. When the raspy sound starts, the loose plastic ring that identifies that cylinder's distributor wire begins dancing, while the others remain quiet. I checked the spark plug, and it is tight.

Any thoughts as to what the issue might be? Does the fact that it occurs only in a range of RPMs rule out a valve problem, or not necessarily?

Here's a video:

http://youtu.be/NPhp0DLesiM

[divace73]

check your alternator and bracket are tight??

[fiatfactory]

.

[KevAndAndi]

Thanks, I'm certainly hoping it's external! Glad I posted, as I don't remember seeing alternator listed as a possible culprit. Will check.

Edit: I had written "distributor" rather than "alternator" by mistake.

[TStark]

I would shortly take off the accessory belt then rev it and see if things improve

[azruss]

check the timing belt backing plates.

[KevAndAndi]

check the timing belt backing plates.

I saw those as possible culprits and I'm pretty sure I investigated that already, but will re-check.

[76was124]

I would buy a cheap stethoscope or use a long screwdriver with your ear on the handle end to locate the source.

Sounds pretty metallic..... couple additional places beyond what was already mentioned would be both cam boxes, head, distributor, fan housing, alternator, throttle plate housing, water pump. Touch each of those areas with the sterthescope , just don't get it caught up in a moving part or on a ignition wire/plug.

If you can't locate it, a compression check might be a worthwhile test to relieve some anxiety.

[Odoyle]

Check the tension on the alt./water pump belt and look for play or warping on the water pump pulley.

[KevAndAndi]

check the timing belt backing plates.

I saw those as possible culprits and I'm pretty sure I investigated that already, but will re-check.

And azruss is the winner. Thanks! That thin sheet metal on the backside of the timing belt cover was always a suspect - it's like the resonator on a Dobro guitar. I had only checked the driver's side, thinking that was sufficient. I didn't hear any change when I dampened that side with my hands. Well, it turned out it was the other, passenger side that was buzzing!

Now, I just have to figure out a way to dampen it. That's a lot easier than dealing with a broken valve spring, or something similar!

[fiatfactory]

.

[KevAndAndi]

Update: Finally removed the timing belt cover, as I am in the process of replacing the radiator and coolant tee, among other things. Discovered why the tin work on the passenger side was buzzing: The ear that attaches the passenger side rear cover to the bracket between the cams was broken. What a pleasure it was to remove those metal plates. The one on the driver's side was a little fiddly, as I had to loosen the bracket that holds the oil dipstick tube.

Once I get my spring projects done, I look forward to confirming that the rasp is gone.