Has anyone else experienced a weird rattling noise when taking off from a stop? I think it's an exhaust rattle but I'm not sure... the rattle is not there if you rev the engine in Park. And, it only occurs at low rpm in DRIVE - it's not there at cruise speed. Just curious if anyone else has had this noise and what was causing it...

Mark

 

Could it be the cat?

 

Could be... I was also thinking of the Mad Squirrel Theory.

On a serious note, it finally clicked in my head this morning as I was driving to work - the noise actually sounds just like the rattle/knock you get when an engine "diesels" after shutting down. I am beginnig to think maybe it's a lifter that's out of whack! Anybody have any ideas??

Mark

 

Sounds like spark knock.

Lifters do not care whether you are idling, or taking off from a stop, or cruising down the road. The valve train will make pretty much the same noises all the time.

Try some different gas and see if it changes.

Could also be an exhaust leak, such as between the exh manifold and the head.

 

I have a 1991 RS, and know exactly what you are talking about. When you take off, theres a weird rattle, but once you get going, it goes away. Oddly enough, it definitely sounds like its coming from the rear (right rear on mine). I thought it might be my 3 inch exhaust pipe rattle or something, but ya, I know what you mean. Its annoying, and makes me feel like I am driving a PowerWheels sometimes.

 

look for a exhaust leak.

 

My 95 S10 Blazer (4.3 liter with the FI set up that almost looks like a tpi unit) was doing the same thing back in October. Pull off from a dead stop and it would almost sound like spark that would go away when the load and rpm on the engine dropped off (right after changing gears). It gradually got to the point where it did it off and on going down the interstate when you'd climb a hill. Had all kinds of oil pressure (50 psi at idle even when warm). At last the #4 rod bearing gave out while it was sitting in the yard and I was revving it up from under the hood trying to find that exhaust leak, sticking lifter, etc. The rpm dropped off, the noise got worse the oil pressure dropped to 20 psi and the engine temp went up to about 220 F. In all my years and all my vehicles and all the hard miles I've put on them I've never "lost" and engine, let alone one that seemed to be in such good shape (oil pressure, mpgs, lack of oil leaks/oil smoke, etc). I had no idea what a knocking rod bearing sounded like. Now I do.