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A rattling sound on engine overrun.

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Hi folks:


When the previous owner went to have an engine rattling sound diagnosed, the tech told them to use a better grade of gas (pinging), but pinging is not what is happening as far as I can tell...


I can say without a doubt that the rattling is not pinging. It happens not under load, but rather on the overrun, when you've pulled your foot from the accel. pedal. It also happens when the engine is revved, again not under load.


I have been told that the driverside camshaft-to-distributor can cause a sound - is it a rattle? The belts are under 20K and I hear no flapping whatsoever that would tell me the belts need a re-tension.


Can anyone tell me if this is a typical sound for the EA-82? Should I stop worrying?


Many thanks in advance,


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Your description sounds exactly like what I chased for 3 months. Only on deceleration, at about 2200 rpm. Like when you rev the engine at curbside and let off the gas. Or when coasting downhill in gear. And only when it was good and hot.


The rattling was my catalytic converter. Without opening up the cat, I can't be sure what happened, but either the "brick" cracked, or it just got loose inside the housing. It took a certain frequency and backpressure to set it up in a harmonic rattle.


I suspected a rod bearing, timing belt pulley, camshaft, distributor, lifters, etc. (got lots of advice for each of those....) I used a stethoscope to narrow it to the exhaust (hard to do when the rattle was so touchy to reproduce). I put the car up on jacks, ran it till was hot, had my wife hit the accelerator while I slid underneath and isolated it 100%.


Ended up with a new Y-pipe. From the dealer, it was only a few dollars more than other options.


So, are your symptoms similar? Check your cat....


-- Mark

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