Backfire on over run

  1. Newbie Joined: May 2012 Posts: 15
    #1
    Bought a 98 Mk1 saxo VTR about a month ago now and at first I kind of ignored the ridiculous backfire on over run as it sounded cool for a while.

    Anyway, now I am sick of it. I cant go anywhere without it backfiring like mad as soon as I let off the gas! I mean even when driving like a granny to the shops I sound like a typical boy racer type backfiring all the way to pulling up to a set of lights.

    Surely this isnt right? Its pretty extreme and obviously wasting fuel, annoying as hell on long journeys too!

    Is this a known problem? What can i look for? I just did a full service and it changed absolutely nothing.

    I know my exhaust is blowing at the mid section due to a hole at the mid box joint and also small hole in the back box joint also.. grr!

    I have had blowing exhausts before though and it never induced backfire.. so what gives?

    Ideas please?

    Im thinking of checking for any leaks in intake mani as this would surely mess up the air fuel mix right? also going to check out the condition of my lambda sensor.. maybe give it a soak in fuel for a bit.

    Also: Where is the MAP/MAF sensor and how do i clean it? Im sure I saw someone on here advocating cleaning this anyway!
  2. Established Member Joined: Apr 2010 Somewhere better than you! Posts: 1359 '98 Mauritius VTR
    #2
    It aint a normal thing mate, i own a 98 VTR and never once had a backfire. Thats about the only help i can be though..
  3. Newbie Joined: May 2012 Posts: 15
    #3
    Quote:
    Originally Posted by JayT439KRJ View Post
    It aint a normal thing mate, i own a 98 VTR and never once had a backfire. Thats about the only help i can be though..
    This is what i guessed I hope i can get some ideas on whats going wrong here..

    It would only backfire if its overfueling esp on overun thats as far as i really understand it. What is causing that I have no idea.
  4. Established Member Joined: Apr 2010 Somewhere better than you! Posts: 1359 '98 Mauritius VTR
    #4
    Thats all way over my head mate, dont have a clue about cars, just enjoy driving them

    Hope you get it sorted
  5. Saxperience Forum Bum Joined: Jan 2008 Down't road from Sheffield Posts: 4641 Was:16v 106 XS ..... Now: Import 1.8 MX5
    #5
    Quote:
    Originally Posted by VTR_rick View Post
    I know my exhaust is blowing at the mid section due to a hole at the mid box joint and also small hole in the back box joint also.. grr!

    Fix that, and chances are it'll go away. I know whenever i've had a blowing exhaust before, it's popped and burbled off throttle.


    If it doesn't fix it, at least you've sorted your blowing exhaust...
  6. Established Member Joined: Oct 2009 exeter, devon Posts: 1224 Clio 172
    #6
    id also say get your exhaust sorted, it definitely wont be helping

    is the car completely standard?
  7. Newbie Joined: May 2012 Posts: 15
    #7
    Quote:
    Originally Posted by BertieG View Post
    id also say get your exhaust sorted, it definitely wont be helping

    is the car completely standard?
    Yeah 100% standard.

    Just ordered a whole exhaust system minus cat (that cant wait till mot time!) as the front pipe is caved in after what looks like meeting a curb and like i said the rest of it cat back is old rusty and blowing.

    Will update when its all on.

    Cheers all!
  8. Saxperience Forum Bum Joined: Sep 2011 Doncaster Posts: 2627 Fabia VRS, mk1 fiesta + some others
    #8
    they rummble and burble abit on over run, but even when going hard it shouldnt pop and bang.
    especially with a standard exhaust system.
    check the air filter isnt blocked causing it to overfuel.
    it could be many things though, mostly sensor related.

    maybe it has anti lag, but no turbo, causing it to retard the ignition 180* so it sparks on exhaust stroke making it pop and bang like a ******* without doing anything.
  9. Saxperience Forum Bum Joined: Jul 2010 South Wales Posts: 3078 ZX 16v, 205 GTI, 309 Goodwood, 405 MI16.
    #9
    Quote:
    Originally Posted by m4tt274 View Post
    they rummble and burble abit on over run, but even when going hard it shouldnt pop and bang.
    especially with a standard exhaust system.
    check the air filter isnt blocked causing it to overfuel.
    it could be many things though, mostly sensor related.

    maybe it has anti lag, but no turbo, causing it to retard the ignition 180* so it sparks on exhaust stroke making it pop and bang like a ******* without doing anything.
    LMFAO.

    this guy obviously doesn't know about the wasted spark principle that these engine management systems run on and the fact it doesn't make one bit of difference.

    my 205 did this till I got the fuelling adjusted, it was running a bit rich, if your lambda is dead it will do this.

    other culprits could be ecu temperature sensor, cleaning parts never helps I find, you just need to test and replace whatever is faulty.
  10. Established Member Joined: Mar 2010 Basildon, Essex Posts: 1042 Citroen AX VTS
    #10
    does it do it even from cold?
  11. Newbie Joined: May 2012 Posts: 15
    #11
    Quote:
    Originally Posted by Gareth_R View Post
    does it do it even from cold?
    Hi Gareth (ax_rick, fellow basildonian from axoc here, feel ashamed to tell anyone I dumped my ax for a Saxo lol!)

    Anyway, yeah does it from cold, even starting her up you can hear poping.
  12. Newbie Joined: May 2012 Posts: 15
    #12
    Quote:
    Originally Posted by welshpug View Post
    LMFAO.

    this guy obviously doesn't know about the wasted spark principle that these engine management systems run on and the fact it doesn't make one bit of difference.

    my 205 did this till I got the fuelling adjusted, it was running a bit rich, if your lambda is dead it will do this.

    other culprits could be ecu temperature sensor, cleaning parts never helps I find, you just need to test and replace whatever is faulty.
    Lol...


    And yeah I fear the lambda is prog knackered. No history so no idea when it was last shown any love