Anyone else had this happen? 2007 with about 100K on it. When I pull off of a 45 mph street onto my street (25 mph) and let of the gas, I can hear a fairly quiet backfire. Probably the cat or more likely a muffler that needs to be replaced? When I search, all I find is people who want theirs to backfire...

 

Is it a backfire or just a pop/bang? After I swapped out my oem mufflers on my '09 GS350 for Flowmaster 40 Originals I noticed the pops/bangs more when downshifting. If you're exhaust system is fully stock I'd suggest checking the cats or your muffler.

 

I would put it on a scanner and scan the fuel trims, you might have something triggering your fuel system to increase fuel. Therefore allowing the spent gas out of the exhaust and igniting. If you dont get this fixed you might have raw fuel going through the cats eventually destroying them.

 

It's like a "Puuhh" sound. A slight pop at the beginning and a soft push of air. Like making a lazy but pronounced attempt and sounding out the "pu" in "push". I'd say the sound is not noticeable unless the music is off and you're listening for it. My exhaust is fully stock (to my knowledge). I do not believe the previous owner (original) modified anything on the entire car.


Sounds like I need something a little more advance that an OBD from autozone/advance auto parts? Do you think I can run it by a mechanic and have them diagnose or do I need to specifically hit up a muffler/exhaust shop?

Thank you both!

 

Yes, you will need a high end scanner with live stream. Take it to a decent independent mechanic or lexus/toyota dealer, have them bill you for an hours worth of diagnostics.

It could also be worn plugs not fully burning the fuel, or not properly gapped. Sticking injectors also, could be a number of things, until you put it on a scanner and see what exactly is triggering a rich mixture.

 

My GS (430) does the same. But I have a straight pipe (bypassing axleback), and it makes that very subtle puh, sound as I left off the accel, it can do it almost everytime I do it too! FWIW, I have the Invidia midpipes mated to it also.

You might just have an exhaust leak though... As that is not normal under MOST aftermarket exhausts (I have the topspeed pro 1 exhaust, i believe, and it never did that before the bypass).

 

That is my thought honestly. An exhaust leak. How could I test that besides jacking it up and taking a look underneath for any obvious holes in the pipes/mufflers/cats?

 

That is what you have to do. There is no other good way to check for leaks.

 

I should clarify. I live in an apartment with no driveway or garage and do not have jacks/stands. I suppose Midas or somewhere similar can do that for me.

 

Yeah, ask nicely or find a place that offers a free diagnostic. Just get it up there and if the leak isn't obvious, start spraying soapy water at the pipes until you see bubbling.

 

If you rev the engine and leave the door open, if you had any major leaks you should be able to hear them whistle and echo from the undercarriage.

 

It's VERY VERY apparent if you have even a pinhole leak.... Like ibidu said... You should hear an unusual sound. No matter how large or small the leak.

I've had it on my DP on one of my previous vehicles, and turbo manifolds also.... It was a needle sized hole but it sure as heck made an annoying "ticking" type noise.

GL OP!

 

Closing the loop on this thread. Went to a local muffler shop and within a few minutes we knew what the issue was. The heat shields on the piping in front of the cats was retaining water and the pipes were just sitting in it and slowly rusting. He replaced the piping and left the heat shield off moving forward. End cost was $180 ($90 for each pipe). Thanks for everyone's help!