P0173 & p0325

[Goliat6288]

What's up guys Ive had a CEL for a while and I was thinking it was still the knocksensor code. I decided to check it and I got p0173 and p0325. Something I noticed is that it tries to stall out whenever I break really really hard. Sometimes it actually does turn off some times it doesn't. I've noticed the rpms drop below 500.
Any help is much appreciated guys. Thanks in Advanced.

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[bigb]

brake booster line is probably cracked or installed in the wrong direction, or your brake booster diaphragm is leaking causing a vacuum leak when you brake

There is a god **** check valve INSIDE the vacuum line. what???!

Check that out, and also do a little reading on the brake booster and symptoms of a damaged one. sounds like textbook definition. you are going to want to find this in a yard since I'd be afraid how much it is new

[Goliat6288]

by brake booster do you mean the power brake unit (thats the only thing i found on the manual)?

oh and im guessing this is towards the braking issue and not the codes right?

[bigb]

I guess that is what Mazda calls it. basically the big round thing in the firewall that the brake master cylindar bolts into.

there is a 1 way check valve inside the brake booster that lets air in when you push the brake pedal. if something is not working properly, when you push the brake pedal you create a vacuum leak into the system. That could cause 173 which is fuel trim malfunction and possibly even the knock code. it would have to be a fairly large leak however to cause these types of codes. but think what would happen basically if you cut a huge hole into your intake. the brake booster moves allot of air.

check out this article or just google brake booster

HowStuffWorks "How Power Brakes Work"

[Goliat6288]

yeah in the manual it calls it the power brake unit. it also has 3 ways of checking if its operating correctly or not. pretty easy tests so ill do them by tomorrow for sure.

it could be that since i do hear wierd noises when i brake. cant really describe them. hopefully if its this it solves ALL the problems lol.

[bigb]

if you do need to swap it out, it's a bit of a bitch to change since the master cylindar needs to come out and you need to do a full brake system purge / bleed. plus all the lines that go from the master cylindar to the abs unit. just be careful not to strip those little compression fittings or you will be swearing up and down. slow and steady with the right tools. dont rush this job, be forewarned.

the booster iteself is easy to remove and the bolts that hold it in place are actually on the inside of the car up near the brake pedal.

if this is the problem, congratulations sir as this is the first and only time i have seen one of these die

[Goliat6288]

yaaay... thank you thank you... ill be shooting myself if it is lol. hope its just the line and not the actual unit

[Goliat6288]

forgot to mention that i reset the codes this morning. and after a couple of miles the cel came back on and it was only the knocksensor code.

[bigb]

peel the onion since that *could* be caused by the vacuum leak in the brake booster. make sure that is solid and then move on to the knock sensor. it's possible you just have a bad sensor since those have been known to go on the 2.5

[Goliat6288]

well i did the tests the fsm said to do and it works just fine
these are the tests:


now im going to look under the hood to see if i see a leak... someday