Symptoms of failing stock BPV or leaking seal around BPV?

L

ljstevens

Member
:
2008 Mazdaspeed 3 GT
Hi All.
Does anyone know what the symptoms (driveability etc) would be in my MS3 if the stock BPV (I hope I am referring to this correctly) was either faulty or the seal around it was leaking or not keeping pressure?
I hope some people will be able to provide some insight. I look forward to reading the responses.
Thanks
L
 
Hi Chimmike.
Ha! I was trying to do it backwards in order to try and get an objective response as possible. I have been trying to isolate the cause of an issue with my car. I have tried changing spark plugs, mass airflow sensor and cleaning the CAI. It is hard to explain, but in summary my car is hesitant/stuttery at low revs when I accelerate and sometimes when I let off the gas. For example if I am on the freeway doing 60mph in 6th gear, I will be doing around 2,000 rpm or so. If I go to overtake and hit the gas I will get some hesitation/stuttering until the revs build to over about 3,500 rpm, then the engine smooths out. Less often, I will get a similar stutter when I let off the gas and I am within the 1,500 rpm to 3,500 rpm range. The way it seems as that it is stuttery until the turbo fully kicks in with all the torque. I had the tech at the Mazda dealership drive it when it went in for a service and he thought it was fine, but I don't think he tried to replicate the same conditions, he just drove it hard. It's almost like you need to go from driving softly to driving hard, and it's in this transition that the issue occurs. Hard to explain with a few words, sorry!
 
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i have experienced the highway driving/accelerating to pass issue you mention a few times, mainly if you just step on the gas and the rpm's are in the lower range, only in 6th tho. i have found that either easing into the pedal to bring up the rpm's, or downshifting doesn't cause the issue.
 
I think the hesitation you are feeling is the boost building. If you are that low in the rpms and you go to punch the gas it is not going to instantly have full psi. If it were me and I wanted to punch it to pass someone I would downshift into 5th. You shouldnt be going WOT, I know you did not say you are or did, lower than 3 grand anyways.
 
^ Agree. This car does not really like sharp and strong throttle tip in below 3,000 rpm. You should be gentle with the pedal position when there is not enough rpm for the turbo to spool properly. That really does not happen on the stock turbo very well until at least 2,800 rpm. Just downshift one gear if you're going to pass and your rpm is less than 3,000 rpm. It should jump up to 3,500 rpm or so and you're good to go.

Also the suggestion that you may have some bad fuel makes some sense. Are you running at least 91 octane, preferably 93 octane if available? Top off your tank with some high octane fuel from a known good source.

Do you have a boost/vacuum gauge? Consider getting one if you don't. They are cheap. Most issues with the stock bpv (and they are rare) is the inablity to hold boost or hit target boost under WOT at higher rpm. That would be obvious on a boost gauge. That does not sound like your issue.

Also, your car is old enough that you may be developing some cracks or splits in some of the hoses and vacuum lines. I've had to replace several. How long have you owned the car and how long has this condition been present? Is this something new or, if you bought the car used, has it been that way?
 
Sorry for the delay in replying. Thanks for all the comments. To try and answer the points. I only use 93 gas from Shell or ConocoPhillips. I very rarely bury my foot for WOT, especially if the car is not up to temperature. This honestly happens even when I only tip the throttle in the rev range I mentioned. My car is an '08 with 72,000 miles. I bought it about a year ago at 55,000 miles. The issue started surfacing about 9 months ago... so since I have owned the car. I originally changed the spark plugs for the Iridium ones recommended on this board. That didn't make a difference. Then I changed the Mass Air Flow sensor and thoroughly cleaned and re-oiled my Cobb CAI. All these changes don't seem to have helped. I will try and look around the engine bay for vacuum lines this weekend, but I am not too sure where to start peeking to find these - is this hard to do? I am mildly competent :) I have changed fuel pumps, brakes and shocks before on other cars.
 
You shouldn't be trying g to over take someone in 6th gear... The 6th gear is meant for cruising... If you going to "over take" someone on the high way do it in 5th or ease your way it the throttle... You should never wot in 6th gear in our cars...
 
^ You replied to a post over two years old. That guy may not even own the car, now and has most certainly long since forgotten about this issue.

BTW: I did go WOT in 6th to overtake a Porsche Boxter S. We were both north of 120 mph on my way to about 160. I closed on him easily enough, but he had more absolute top end and pulled away when I became drag limited. I'll not disclose when or where this encounter took place.

Your response is way too general. Actually, there are ligitimate conditions to use WOT in 6th, but you do need to make sure your engine will be above 3,000 rpm when you do. That means about 80 mph. 5th is good to 120, and is preferable, from a gearing perspective until you pass 120. It is good for general highway speed passing.
 
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A friend just blew up his MS3 WOT in 5th, it's never a good idea if you are running over stock boost.
 
There are threads about this phemenon over on MSF. I'm assuming your friend went WOT below 3,000 rpm and loaded the engine when at low moment of inertia on connecting rod movement and at max torque when coming up on boost. That seems to be when most if those cases happen.

There is no benefit in going WOT below 3,000 rpm, and some risk. I don't think you meant to imply that we should not use 5th at all.

None of this pertains to leaking bypass valves, though.
 
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