Rattling noise from engine

Loose timing chain?

Loose alternator mount?

I had an odd buzz that came in at certain rpm's. I thought it was something wrong with the starter motor as the source seemed to be from that location. It turned out to be the bottom bolt for the intake plenum's brace was loose. That brace is right at the front of the starter so I wasn't too far off...

My eL-cheapo version of a mechanic's stethescope is a length of 1/2" heater hose (about 18"-24"). Hold one end to your ear and aim the other end at any suspect areas. Be careful not to get your fingers near any moving parts (or we'll have to nickname you 'Lefty'...)

Songs like pinging/knocking to me if it's only under load. Could also be rod bearing or piston pin, though less likely. That would rattle on the overrun, under no load, too.

Andrew

Sheesh, how about sounds instead of songs? Ouch.
Andrew

Exhaust has a harmonic resonance that sometimes does weird things. To dampen the resonance,
I have seen cars with two plates bolted together at the down pipes about 10 inches before the two pipes join into the cat. The bolt goes between the two pipes and the plates just clamp down on the pipes to eleminate the resonance. The bolt could be loose and causing the rattle.
These plates are on my 91 and I have bumped them going over a grass bump and they rattled until I replaced the bolt and tightened them up.
Grabbing at straws. Heat shields and timing chain, Power steering pump mount.
Good luck!
Stan

If your car has air conditioning, check the front of the compressor. The front bearing has a dirt shield that goes to pieces sometimes if the bearing's faulty. Or could be the compressor clutch, also.

Another thing is the compressor pullley rubs on the front sway bar when the motor mount sags too much !

Stan Murray said:

Another thing is the compressor pullley rubs on the front sway bar when the motor mount sags too much !

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Agree. Sagging mounts are a recipe for many problems.

I had the EXACT same problem, turned out the intake cam was too far advanced for some reason, when the VVT kicked in under load, it advanced it even further. Check your cam timing! Loose chain is not likely as it spring loaded, unless the spring broke, but that is not likely again.

Thanks for all the responses. She's at the mechanic's right now, so we'll see what happens. I will post the resolution (hopefully) tomorrow!

ddouglas77 said:

Loose chain is not likely as it spring loaded, unless the spring broke, but that is not likely again.

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The chain tensioner does have a spring to 'help' push the tensioner out. However the tensioner is known to hang up and the spring is often not strong enough to overcome such a stuck tensioner. The suggestion is to use a long screwdriver as a lever to make sure the chain is properly tensioned -and not to rely solely on the spring behind the tensioner.

Plus, once 'tensioned' it is locked in place by a wedge shaped key. Thus the tensioner does not remain under the influence of the spring (the spring that is often not strong enough to properly tension the timing chain in the first place...).

ghnl said:

The chain tensioner does have a spring to 'help' push the tensioner out. However the tensioner is known to hang up and the spring is often not strong enough to overcome such a stuck tensioner.

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You are thinking of the 90+ engines, right? I was told the tensioner on these don't fail (even though it is possible).

ddouglas77 said:

You are thinking of the 90+ engines, right? I was told the tensioner on these don't fail (even though it is possible).

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AFAIK, the tensioner is the same for all the Alfa Spider engines. Certainly the 2.0L ones.

ghnl said:

AFAIK, the tensioner is the same for all the Alfa Spider engines. Certainly the 2.0L ones.

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I thought some were adjustable and others are not, just what I was told, I don't know for sure as I only have one engine for comparison and it is definetly not adjustable.

OK, got her back last night after taking a ride with the mechanic. He id'd the sound as engine ping, so we talked about fuel. He recommended Sunoco Ultra or Hess premium - stay away form Mobil/Exxon and discount fuel products due to the additives. We live in western NY which he said is a test bed for Ex/Mo and they do not disclose the additives. The Porsche dealership where he now works is currently involved in a study with a major university engineering dept wrt to fuels. He told me that many newer Porsches are experiencing major failures of compoenets of the fuel system and it seems to be related to fuel. I will try this first and see what it gets me. With only 38K miles on the engine, he didn't feel that there shuld be anything to worry about just yet, but if the fuel change doesn't work, we will try other things. I will keep you all posted (no pun).

I had a similair noise at high revs. Turns out it was motor mounts. Seems the fans was just touching when the engine reved but just missed at an idle. 10 hours and a few chunks of knuckle skin latter - no noise. BTW it was a '71 with 63K miles. The mounts had sagged all the way down to lay on the lower retaining bolts. ( Thanks to the forum for suggesting I check them)