Engine Knock - Chicago Area

M

MazdaSpeedMason

Greenie N00B Member
Hey there!

I've been a forum lurker ever since I bought my 2007 Mazdaspeed 3 about 3 months ago (I bought one of the ones from Cars n' Bids, for better or for worse...link below). Absolutely love the car, way too fast for it's own good, especially on those back country roads. But...now the engine has gained a knock when letting off the gas, but not on acceleration. I'm turning to the MS3 pros in the hopes that I can find the fix (or least locate a good local mechanic). Fingers crossed. (Sorry in advance for the long read, tried to be as comprehensive as possible).

2007 Mazdaspeed3 Grand Touring auction - Cars & Bids (carsandbids.com)

I'm a bit stumped on what it could be, have searched around the forums and worldwide web to no avail. I have put a few more details below on work done and my attempts at diagnostics - would appreciate any help or ideas! Also if anyone has any trusted mechanics in the Chicagoland area, I'm all ears.

The detailed problem: I've put about 7,000 miles on it since buying (120k now) and have had a few issues. Had a cylinder 3 misfire code early on, but replaced the fuel pressure relief valve (stuck open) and everything straightened out. Replace RMM at ~119k. It has been running a bit rough/loud for the past ~500 miles, almost like a loud lifter tick - wondering if carbon build up/EGR valve/PCV valve issues exist. Engine began knocking the day after a long 200 mile drive after a bit of a high rev pull (~6k RPM). Immediately turned the car off and checked the oil, which was super low, just my luck (a smidge under the Min line). Massive oil consumption came out of nowhere (changed the oil ~600miles before). No CELs or smoke coming out of the exhaust either.

Have only turned it on twice since the original knock. Doesn't seem to knock below ~15mph, once above ~25 it'll knock on deceleration...

So two questions:
- Ideas on what the problem is? Or diagnostic steps I can take? (I'm going to pull out the spark plugs and borescope the cylinders this weekend.)
- Any recs on local mechanics in Chicago?

Side note: If you're reading the CnB Listing, the oil consumption noted was actually fixed by the owner (loose oil line somewhere leaking), he just never drove it enough after the fix to notice that it was solved, so this oil issue is a new deal.

At a loss for what to do, any input/wisdom/gallows humor would be greatly appreciated!
 
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Oil consumption could've the pcv valve

Since it only knock on deceleration I would start by looking at the motor mounts and CV joints
 
As bunny said oil consumption can be that PCV valve failing, messed up crank case pressure also seemed to be to cause of all those smoking gen1 turbos they made some revisions in gen 2 to the VC and connection to the TIP that seemed to help matters.

Check those engine mounts, not uncommon for that passenger mount to die, rear motor mount if it's OEM allows for allot of engine movement even when new so after all these years it could just be tired.

How much knock are you seeing on decel? Are you engine breaking?
 
Bunny and Awa - thank you both, incredibly helpful!

Forgot to mention, I replaced the RMM with corksport about 1k miles ago. Definitely could feel engine vibration much more through the butt dyno. Maybe that caused faster wear on the side motor mounts. Unsure how to diagnose if the side motor mounts are bad - just looking at them?

Makes sense about the PCV as well, was on my list of fixes before the knocking.

Awafrican - the knocking is timed with RPMs and hits once per rotation on decel and honestly sounds like someone lightly hitting the side of the block with a wrench, very noticeable inside the cabin, cringe worthy noise. I don't engine brake/haven't been on the MS3.

Hoping it's not a ringland issue or something on the bottom end *fingers crossed*

It's just odd that the knock is on decel only...assuming if it were internals it'd be a-knocking full time?
 
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If it was rod knock you would hear it at idle

Check that the bolts on the rmm are still tight. Check that all of your wheels are tight
 
That is a great point Bunny...especially your earlier CV joint comment.

I also forgot to mention that I replaced the tie end rods on both sides about 300 miles before the clunk...had a struggle getting the passenger side off/back together. You're CV joint wisdom may be the culprit. You're a wizard...

Really appreciate all your help on this.
 
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Quick follow up to the above - I stuck my head in/under the car,

- CV joint boots seem solid, no leaking or tears, doesn't seem to be any play when grabbing them - is there another way to confirm that they are the issue?
- Without taking off the reservoirs - passenger motor mount is definitely old and dry, and there's a minor tear on the top (from what I could see), if it were truly shot, how evident would it be?
- Wheel lugs were tight
- RMM bolts - will need to check that out this weekend

On the tie-rod ends - I replaced them then drove ~200 miles with it a smidge out of alignment (was hoping to replace ball joints before I got an alignment done). Is it logical that that could have caused some CV failure?

Apologies for all the questions and thanks for everyone's patience! Still hoping on a prayer that its not an engine issue :frown:
 
Reds Garage in North Aurora IL

Derrick will take care of you. Super honest guy and owns a couple Speeds himself. Always 3-4 in the lot at any given time!
 
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