2005 Mazda MPV. 77000 miles. Months ago threw CEL's that since disappeared. One was for misfire the other for the cat. Sluggish and uneven acceleration for like 6 months. Cleaned MAF sensor and IAC but they weren't very dirty. Checked under and a hole in the flex pipe between 2 cats.

No CEL so it's likely not the o2 sensors. Is it a hole that just develops from rust or whatever and causes exhaust leak thus making acceleration sluggish and eventually the hole getting bigger and bigger? Or is it because of a clogged cat?

 

A couple things can cause it to break.

I would say number 1 would be rust.

Number 2 can be bad motor mounts causing the engine to move too much causing the flex pipe to break.

Is it a hole or a crack? Take a pic.

 

It's a hole so I'll rule out motor mounts. I hope it's rust as the exhaust leak could've made the car sluggish through acceleration until the hole ultimately popped open.

 

if you have an exhaust leak, then yes you will be losing backpressure which causes you to lose torque off the line when accelerating... if it feels like you have to put your foot down much more for the car to move, then it would be due to the leak.. if you live in an area of snow, the salt from the winter wreak havoc on exhaust systems... but there is always moisture inside the exhaust system that can cause it to rot from the inside...

i have never seen a clogged cat occur before...

did you check the tube on the PCV valve? if i recall on the MPVs it was common for the tube to collapse causing rough idle and poor acceleration..

are you a member of any of the mpv forums? i would try there too...

 

A clogged cat will not create a hole in the middle of a pipe unless there is severe rust. I would think if it rusted through, it is a normal carbon steel pipe and not the stainless like most have. Replace it and the problem will probably go away.

A blocked cat will give you very sluggish acceleration. You could always knock the ceramic out and see if that solves your problem, but you won't have enough back pressure but acceleration will be better.

 

trying to learn here....

could heat have caused that too ? heat and vibration causing it to break ?

 

you mean like heat causing the exhaust pipe to create a hole in itself? highly doubt it... the hole must have started from a rust point where it began to eat itself eventually through the pipe...

 

I actually changed the tube to the PCV valve as it is a common occurrence last year. I am a member at the MPVclub forum and they advised me to check for any CEL's even though I don't have any as it could be from misfiring, o2 sensor, etc. Would it be wise to just change the flex pipe and go from there? I hope it was just rusted so I don't have to mess with emissions or engine stuff. Thanks for all your help everyone.

 

if the flex pipe is indeed compromised, i would go ahead and get it changed... it shouldn't be expensive

if the hole is only on one side, you could try patching it by wrapping with some exhaust tape... that should help give you an idea if your problem is with the exhaust... your accel should improve by sealing up the hole...

 

Think I can wrap this?

 

I called Advance. I know it's Advance but he didn't recommend the wrap kit even though it was just $11. He said just take it to a muffler shop.

 

wow that is a big hole... i didn't realize u could fit your fist in it... that is prob where you are losing backpressure... def get that replaced... you will just waste the 11$ by wrapping it...

felx pipes are always know to rot out faster due to the way they are built... water splashes up and lodges itself into one of the seams and it will just rot from there... i try to stay away if possible... has any of the MPV guy been able to switch from a flwx pipe to a rigid pipe? maybe a muffler shop can cut that section out and just weld in a pipe of pipe...

 

replace it.

 

Wow. That is a big hole. Definitely replace it.

 

Not related to the busted pipe but what is the condition of your plugs?

 

I spoke to a muffler shop that my friend recommended and they said if their universal fits it'll only cost $90 installed. I'll see on Saturday.

Yeah it might be a good idea to do my plugs soon at least before I start changing coils which tend to go bad on this car. I only have 70k miles but not all cars are my Accord. I'm like 4 payments away from paying off this puppy too so looks like repair money will replace note money.

 

do the plugs at 60k, then the coils at 90k... should be a good tune-up interval for these vans...

 

http://www.flickr.com/photos/53052618@N08/6038414036/

http://flic.kr/p/acxEtg

Bad o2 sensor as it's white. Cat clogged (after flex) so changed that too. O2 went bad and fucked both cats. Muffler shop can't do cat Nor o2 in it (cat before flex). That cat is showing wear as well. Still don't know why. $300 so far

 

P0302 cylinder 2 misfire. Coils are a common issue. Should I go plug first?

 

I spoke to a mechanic at a local joint and he said dont bother with the o2 and other cat yet. Do coil first. With my luck it's the rear one which means manifold removal. Happy BDay to me

 

Update: Changed out rear coils and plugs works like a dream. Took me 7 hours for intake manifold removal, TB removal, unplugging a lot of stuff and of course bolts. My hands are still black with red cuts everywhere but it saved me $200. The plugs were black and one was cracked. At work in pain.

 

Wow....7 hours. I thought the I35 was a PITA at 4 hours.

Look at the cuts and bruises then at this.....



It makes the pain go away. It may be a PITA but nothing easy comes cheep. I did the plugs on my I35 twice, Pathfinder and my TL. All total I probably saved about $600 doing the work my self.

 

Nice work, it's amazing how long it takes to do this stuff sometimes.

 

Props to you on DIY.

and wow that's a BIG hole.. haha definitely wasn't expecting that.

 

Thanks for props. I should've taken a pic of the plug. That thing was done. I'd post the pics that someone posted for the install but it pains me just to see that bay.

 

Do it.

 

As you wish. Just go here and scroll down

http://forum.mpvclub.com/viewtopic.p...er=asc&start=0

 

The problem came back after a week with my wife driving. No CEL and when I got home and drove it to Advance it drove fine. I still see old codes and the Advance guy said it might still be running open loop and I have "sleeping modules". Ideas?