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Thread: 08 MPS boost cut?

  1. #1
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    Default 08 MPS boost cut? UPDATED

    hey all,

    recently my fiances 08 MPS3 has been feeling abit sluggish. also couple of nights ago when we went for a drive into the city, we had 3 people on board and i planted the foot down in 2nd gear and it reached about 5k rpm and all of a sudden had a big 'jolt' - feels what i believe to be a boost cut (going from experience from my previous cars ive had)...

    to confirm this i thought i'd load it up in 3rd gear, and it did the same thing but at a lower rpm (4k rpm)... has anyone had this problem before and anyone know whats wrong - or have an idea? there are no engine lights, temp gauge is looking normal, and in fact the car drives like normal and behaves well off boost.

    i will be ringing the dealer on monday and will book it in asap to get it looked at and probably do its 30,000km service on it at the same time...

    its currently got 27,000kms on it, last service was done at 20,000kms however this wasnt done at a mazda dealer - not sure if this is a problem as like some manufacturers for cars and bikes now they have to reset something in the ecu (like a service interval light) though i havent heard of anything for the MPS3 as such?

    and for your information the car is completely stock, no mods whatsoever... its a 08 MPS Sports model

    any help or feedback would be great and much appreciated
    Last edited by marbs; 28-10-2009 at 08:05 PM.

  2. #2

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    Being un-modded I have no idea.

    Was it a cool night?

    Have you driven in dirty/dusty conditions? Has the MAF been cleaned recently?

    These may cause irregular conditions/circumstances.

    We are all yet to discover why/where boost/fuel cut issues arise. Some say load vs boost etc.

  3. #3

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    It was a cool night, but nothing too cool like a winter's cold night... and if it was a cool night and boost spiked then fair enough, but this seems to happen as soon as boost barely kicks in, so it doesnt even feel like its reached anywhere near full boost (not that I have a gauge installed or anything)...

    No I haven't really driven in any dusty/dirty areas, ie. dirt roads or NSW/QLD's orange dust storm but no I havent cleaned the MAF before... might look into it....

    ---------- Post added at 03:39 PM ---------- Previous post was at 03:38 PM ----------

    ^^ oops posted on my fiance's account while she was still logged in, oops...

  4. #4

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    Wouldnt be the stock bov would it?

    Have to admit turbos are not my area of expertise...seems feasible though.

  5. #5

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    wouldnt have thought it'd be the BOV? if the BOV was leaking I'd be guessing you'd be losing a few psi in boost pressure, but I wouldnt think it'd cause a 'cut/jolt' of any sort... ill keep that in mind tho...

    also just checked the MAF and it seems to be pretty clean! thats not to say its not it unless its a faulty MAF.. but if it was faulty i'd be guessing i'd at least get a fault code/engine light of some sort...

  6. #6
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    Fuel related?

    Has it been filled at a different servo to normal in the last tank?

  7. #7

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    thats what I thought originally too and asked my fiance, but she said always BP ultimate, so nope...

  8. #8
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    In that case I'd be checking all the intake pipes/hoses for leaks or splits, associated pipe clamps for tightness etc. Sounds like some extra air could be coming in...

    Or just take it to Mazda for the service and tell them about it (or even better take them for a spin and show them).

  9. #9
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    It could definitely be a bad batch of fuel..
    is it idling roughly?

  10. #10
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    Quote Originally Posted by WombatMPS View Post
    thats what I thought originally too and asked my fiance, but she said always BP ultimate, so nope...
    I have gone off BP Ultimate since having a couple of dodgy tanks a while ago, I was getting a fair amount of KR (knock retard) on the Dashhawk even to the point of it causing the engine to stutter.
    A coupe of degrees of KR at WOT will feel a bit like a cut scenario.
    Try a different brand of fuel, personally I now use Mobil 98 and have never had a problem with it.

    Otherwise, as mentioned, check all the hose clamps, especially the one on the turbo inlet, they are renown for coming loose.
    Nearly all men can stand adversity. But if you want to test a man's character - give him power.
    Abraham Lincoln

  11. #11
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    The MPS's are very fuel sensitive, if the hoses all seem OK I'd still be leaning towards a bad batch of fuel being the cause.

  12. #12
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    Default

    i've booked the car in to get looked at this friday so will see how that goes... but yes it could be a bad batch of fuel... will keep that in mind also...

    ive had a quick check over the car n hoses n everything, and it all looks to be in order... no kinks, nothings pinched, not loose or no splits that i can see...

    bad batch of fuel seems the most feasible at this stage... but we'll see wot mazda says...

    ---------- Post added at 09:21 PM ---------- Previous post was at 09:16 PM ----------

    btw jmac, yes the car is idling perfectly... not rough or anything at all....

    really its on WOT when i load up the car at a lower rpm, it cuts just before the car gets going.. so hasnt even reached anywhere near full boost yet....

    but ive noticed aswell that sometimes on part throttle, it seems to hesitate (on boost).....

    anyways will keep you's informed, but i appreciate the ideas being thrown around.. keep them coming if u can think of anything else... really strange since no one else has had this issue either... so im hoping its something minor.. like a bad batch of fuel.. but i dunno if the mazda mechanics will be even able to tell this?

    ---------- Post added at 09:24 PM ---------- Previous post was at 09:21 PM ----------

    what i might do is this week when my fiance fills up, i'll get her to run the tank down, then get her to put in mobil synergy 98 fuel and see how that goes....

  13. #13
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    Quote Originally Posted by marbs View Post
    l....

    really its on WOT when i load up the car at a lower rpm, it cuts just before the car gets going.. so hasnt even reached anywhere near full boost yet....
    theres the missing piece to the puzzle, loading these engines up at low revs is a no no, particularly in the higher gears, i.e 5th gear, 2k rpm + WOT = Knock Retard, the engine is pulling timing to save itself from harmful detonation.

    There are a few threads covering the topic, as a rule of thumb if you need to get somewhere quickly from cruising in a higher gear, drop a cog or two, then plant it, your engine will thank you for it, and its more fun too.
    Nearly all men can stand adversity. But if you want to test a man's character - give him power.
    Abraham Lincoln

  14. #14
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    Just thought of something else...stuffed O2 sensor

  15. #15
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    Quote Originally Posted by MattMPS3 View Post
    theres the missing piece to the puzzle, loading these engines up at low revs is a no no, particularly in the higher gears, i.e 5th gear, 2k rpm + WOT = Knock Retard, the engine is pulling timing to save itself from harmful detonation.

    There are a few threads covering the topic, as a rule of thumb if you need to get somewhere quickly from cruising in a higher gear, drop a cog or two, then plant it, your engine will thank you for it, and its more fun too.
    the only reason why i was loading it up in 3rd was because i planted it in 2nd gear while rolling and it hit the cut... thinking maybe because the car is governed by boost limit in 1st and 2nd gear, hence why i tried 3rd...

    fair enuff loading it from 2k rpm, but even from 3k rpm? if thats a problem, that sounds like a crappy design (ecu) to me...

  16. #16
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    At 3k it's well into boost...

    Will be interested to see what Mazda says.

  17. #17
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    Quote Originally Posted by TallDan View Post
    Just thought of something else...stuffed O2 sensor
    would a stuffed o2 sensor cause such probs? as far as i knew from other cars/past cars ive had, o2 sensor really only works when in closed loop (when cruising) for good fuel economy? so at WOT or opening/closing the throttle (part throttle) shouldnt have any affect? unless its different on the MPS3's?

    yes will be interesting to see wot they say... but fingers crossed maybe its a bad batch of fuel and after my fiance has run the tank low and filled up a new batch of fuel.. with a bit of luck the problem might 'disappear'

  18. #18
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    Not 100% sure to be honest, just threw it out there as something else to look at as they're a semi-common replacement on these things.

  19. #19
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    well like most of you suspected.... it was bad fuel!

    my fiance ran the tank down then ended up filling up the car with mobil synergy instead of the BP we're used to....

    power is all good, no hesitations and no cut outs of any sort (boost or fuel)..

    even loaded up the car with 3 ppl on board, 3rd gear, 2k rpm and WOT and it pulled fine all the way through the rev range...

    thanks everyone.....

  20. #20
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    Good to hear you got a resolution. I use BP Ultimate also and had one servo in particular where the car always ran like crap when I filled up there, I suspected that their Ultimate may not have been all that...

    So now I have two servo's I regularly fill up at and have never had a problem at either.

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