02 GAGT Severe Intermittant Startup Knocking [Archive] - GrandAmGT.com Forum


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11-05-2007, 10:02 AM
This started happening about 7K miles after getting LIM replaced (63K on an original LIM is apparently good) at dealership (crappy work done by them btw). After the engine has sat for a little while after use (still warm), or first thing in the morning, when I start it, it has intermittent knocking that is extremely loud. I remember lifter knockings from my old 79 Chevy, and it dont sound anything like that. This sounds like a big old Ford diesel revving it up when I start it. The sound will die out slowly as the engine warms up. I've read about the piston slap and thought it might be that. If I kick up RPMs to around 2500 and let it go, the sound goes away and comes back. I've tried better octane gas, with no results. Gas millage has been constistantly around 24-25MPG, no drop in mileage. It seams to be occurring more often than not now. I can start it, back it out of the garage a few feet. Work on something about an hour. Hop in, start it again, and it will be banging away. I tried to zero in on where the sound was coming from. It is loudest under the vehicle. I can hear the lifters when I listen to the top side of the engine, a definite separate sound. When I am under the car from the sides, it sounds like it is coming directly from the catalytic converter.

Can this be symptomatic of the dealership breaking something?

Is this a symptom of the knock sensor going bad???

The sound never returns when driving the car, or letting it idle. When the sound goes away, it stays away until the car is stopped for a while. I assume if it were lifter/rocker arms it would continue while the engine was running. I notice no loss of acceleration or power. It is just almost defening when starting my car with the windows open. Any help would be appreciated. I would take it to a garage for diagnosis, but it is not consistant enough for me to show them on the spot, nor can I be without my vehicle for them to try starting it the next day. I also cant be without the car for too long while it would be repaired (if it needs it). I wish I could just dump it off as a trade in, but cant afford a new car either.....

I throw myself on the mercy of the great mechanics here for assistance....

Thanks in advance!

11-05-2007, 05:24 PM
Does it sound like our car?

if not go back to the dealer and bitch.

11-06-2007, 10:08 PM
My car makes that sound too. its just because the engine is cold so all the metal parts are not expanded to where the need to be. all cars to that to some extent. it goes away after the car warms up.

11-07-2007, 07:04 AM
If this were a light knocking, I wouldnt mind. But the level of sound that it is putting out when it does it is loud enough to hear throughout my house when it is in the garage. I would compare it to the level of sound that a big rig puts out.

Plus, it will occasionally happen when the block is still warm, not cold.

11-07-2007, 05:44 PM
take it back to the dealer.

11-07-2007, 09:25 PM
Mine is loud also, i would like to see how ppl play this out. The main two noises i hate, Cold start knocking and that damn A/C compressor grinding.