Rattling under load
 

Ok so here’s my story,

just installed completely new timing chain kit vvt and all, replaced turbo core, exhaust manifold gasket, new battery, new plugs. So in park it runs and idles great, revs up no noise. Although at idle under the hood it sounds like the high pressure fuel pump ticks. While driving however when pushing the gas pedal to accelerate it rattles like valve train noise. I have a hard time pinpointing it as I’m driving. Could I not have the timing correct? Or maybe the vvt solenoid? I feel like I’m getting $100 dollared to death here lol. It really doesn’t sound like a heat shield but more like valve rattle. Any help would be appreciated

Timing off.
 

The timing is off a little. If it runs smooth and quiet until boost starts building, then starts rattling, its valves slapping pistons due to the advancement of timing from the vvt adjusting and advancing the timing while under a bigger load.

I had/have this exact problem. I assumed it was timing chain related and, due to the many timing chain related problems with this motor, I went ahead and had the timing chain replaced...at a Mazda dealer....last week. The 'rattle under load' is still there. I picked it up last Saturday and plan to take it back and have them look at it but wouldn't you think they would have properly set the timing?

Update: I'm taking it back later this week...We'll see what they find.

Dealer says I have a cracked exhaust manifold...causing more work for the turbo...causing the noise.

So...what was the problem/solution? Engine timing? I have a 2007 CX-7. According to the dealer I bought it from, the transmission was replaced and the timing chain and tensioners were replaced. Still sounds like a bucket of marbles was thrown into the engine when I accelerate. It's quiet while sitting idle and while cruising, once I get up to speed. Sounds perfect while in park and bringing RPM up to 3500-4000.

Well, the short answer is 'I don't know'. I took it back to the shop one more time, drove around the block with the mechanic in the passenger seat and he said it was the turbo.
Not having 3-4 grand(?) laying around to replace it, I just let it go...and kept driving it like that...for 3 years. It still ran just fine, great in fact, just had the noisy acceleration. A year ago I handed it down to my daughter to drive. Sometime in that year it just stopped making the noise!? She never noticed because, well she just turns the key and goes, so.
It still runs great, though I have noticed a little chatter at startup when I've driven it lately.
It's got 160,000+ miles on it now, and still runs great and suspension & everything is still tight. I did have to replace one of the rear bearing assemblies last spring. Going to just drive it...well daughter is...until it won't.
It's in my garage right now though...has had a small oil leak for a few months now so I finally tackled re-sealing the oil pan. It worked but in the process noticed a drip of coolant coming down from the back of motor. Found a coolant leak at the small line going to the turbo. Also had to order the air intake connected to the turbo cause it cracked while disassembling it all trying to get to that water hose.
So, sorry I don't have a definitive answer for you....just keep driving it I suppose. From what I've read/learned, the key to keeping these motors running is be diligent, very diligent with the oil changes.

Thanks for the reply. I know this thread is several years old and wasn't expecting a reply at all. So many times, a post is made and the OP never comes back to "finish the story". I greatly appreciate it. I'm going to take this one to a mechanic I trust and let him see what he can do with it. I got this one for a steal and hate to think I wasted my $$. If it's too costly to fix, then I would've been better off putting a new engine in my previous vehicle, the one I bought this one to replace. Oh well....we'll see ;) Thanks again!

Did you find out what the problem was?

Good luck! I bet it still has a lot of miles left on it.

Thanks! It currently sits at 92k miles