I've just started to notice a noise which is usually the most noticeable when starting from a complete stop. It's hard to describe, it sounds like a low power steering groan with a slight vibration / shudder quality to it. it seems to be coming from the engine area, but I think it is chassis related. I recently replaced a cracked oil pan and switched back to the stock exhaust and PCM to pass smog. Any thoughts as to what this could be from?

thanks

 

Is it possible that the exhaust or something else attached to the engine is also touching the frame somewhere? Or the body? Those types of noises transmit directly into the cab, and since you just replaced a few things I'd start there.

 

That definitely could be what's happening. I haven't had the chance to take a good look yet, it's pretty much dark out by the time I get home from work. I'll take a look this weekend. Right now I'm wondering if this is something anyone has experienced before. Thanks for the response.