Just noticed this new noise over the past few days. When the car is cold, within 10 minutes of starting a rattling-type noise can be heard from the engine while idling at its lower RPM. It almost sounds like a very very mild version of the sound you would hear if the car was running out of gas or air, and basically about to stall. You could also say it sounds like a diesel engine. It seems to be coming from the intake/heads area or the timing case (which could be wrong).

I drove the car around my cul-de-sac to see if it gets worse at slow driving and it did! But it only makes noise when the car is off a fresh cold start. The noise seems to be replicated when I push the gas and let the RPMs go up and then immediately let go and let the car jerk forward while it slows down under its own weight and RPMs. This also happens when I let the car idle down in any gear after just giving it gas. Seems to support the lack of air/gas theory.

Anyone have this happen before? The most recent modifications that could have caused a change in how the engine performs are: Strup test pipes, Motordyne MREV2 and Motordyne 5/16" spacer. I also have an Injen short-ram/CAI (in short-ram form now), stock headers, Top Speed y-pipe, and Top Speed mid-pipe and mufflers. I checked under the car and around the engine and everything seems to be in its proper place and no visible leaks anywhere.

I had a friend ask a friend of his that knows a lot about engines and he suggested that if I am getting noises after letting off the throttle it usually has to do with the intake system, where I am not getting enough air possibly through the tube or the manifold. Could this be a possibility from having too much air going out via having a straight-through exhaust system like I have now? I figured putting in the MREV2 and spacer would help this problem.

Any tips? Suggestions?

 

1) check the brackets (that mate to the tranny) of your stock cats to see if they are broken, which can cause a bad rattle.

2) check to see if the flex-joints on the ypipe are broken; a better check would be to put on your stock ypipe

Hope this helps

 

I think the noise is definitely engine internal is what it sounds like. I took it for a drive today and it was doing it pretty bad while letting the car idle down in gear. It almost sounds like a diesel engine when it idles.

 

i'm having the same problem right now. taking it to the dealer

 

It only does it for the first 10 minutes after a cold start?

Does it smoke at all?

I would get that checked. It may be one of the revup oil consumption engines.

 

No smoke.

I got my test pipes welded on to the bracket for the CATs and the noise seems to be gone now.

 

grr i have that same problem and i have been trying to find it since i got the car...its like he said only when its warming up...maybe the gaskets are old on the exhaust due to the heat and warped or the bolts are old and rusty...ima have to put it on the lift and see