Massive loss of power



  • Hi Guys,

    I have a mx3 1.8 ( there could be possibly different engine in it but not confirmed)

    I have her as a track car and was out today and there is a pretty big problem

    Problem is, I am coming down the straight, about 60/70 in 5th, heading for a hair pin turn, brake,change down to 2nd, turn in and when I put the foot back on the pedal, the power totally goes from the engine, after a second or two the engine seems to kick back into life.

    I have used the search button and looked through the manual so could be one of many things? Any ideas? Heat temp sensor? Possibly over fueling?

    I have a 4 inch straight through from the cat and the air cone filter replacing the orginal boxes

    Need to get this sorted quick

    Thanks in advance



  • If you do not have a full induction kit then you must still have the the plastic hose on for the sensor and filter to fix to.

    The plastic hose does not get any support when you remove the filter box and just put a cone on, I bet if you take it all off the hose will have a load of tiny cracks in it that let in air and give a false reading and screws the cars head up. If it does its time for a proper induction kit.

    If not, it could be a sensor somewhere giving up, you may have air getting into the crank case that can cause that sometimes or even a lead leaking electricity back into the block can cause that.

    The best way to check is if you open the bonnet at night you will see tiny blue sparks dancing all over the place, check all the leads out of the sockets as I had one go on the plastic part and had cracked a little and that caused the same thing. If its not induction or electrical then go down the route of pulling codes to find it



  • I rekon dizzy or dizzy cap starting to give up the ghost. Would generate alot of heat during track use and as dizzy is bolted straight to engine heat damages them easily. Check dj's suggestions first tho as they are the common ones.



  • Cheers lads,

    Marco, you can see the set up I have at http://www.uk-mx3.com//forum/viewtopic.php?t=2187&start=15

    I actually ended up pulling out the extension hose and moving the cone directly onto the VAF.

    I dont get the bit about opening the bonnet at night? Like lift if up with the engine off and I could see something?

    Is there a heat temp sensor somewhere that could be faulty? Possibly one on the crank?

    I have looked into it a little and people with similiar faults have replaced fuel tanks/lines/filters because of rust?

    Also I see Jesta had a similiar problem, my problem is not exact but maybe it feels more extreame with higher speed and braking.

    On the manual, there is syntopms of this in the Fuel section, I might try as much as I can this week before I send it off, I think its only something simple, annoying though…grrr



  • the leads short out onto the metal work when they start to wear, check at night in pitch black to see if you can see any sparking caused by leads.



  • Mine isnt fully cured, though I dont have reason to suspect any sensors are broken, Ill be fitting new HT leads and plugs in the next few weeks as theres a misfire on occasion, Im expecting that to fully cure the problem.

    It was half fixed by properly setting the idle, iac, tps and the IAA screw. I went for a drive to fully warm the engine, then I put it into diagnostics mode (TEN+GND), started engine again, then wound the IAA in fully, then increased the revs using the throttle stop screw so it wouldnt die, then checked the rev counter, adjusted to 700rpm (or as close as I can tell) stopped engine, adusted the tps to read properly from the new idle setting, took out of diagnostic mode, started engine again, then adjusted the IAA screw so as to bring it upto 700rpm again (it dropped by about 100rpm once it was taken out of diagnostics mode) that made the car alot more easy to drive. What I realised was that the butterfly valve was fully closing when the throttle was released, suffocating the engine and making the idle circuit work overtime.

    Though it still has the minor problems when its cold, but I believe this to be ignition lead related as in the morning ive popped the bonnet a couple of times to find that the engine rocker cover is damp/moist/condensated, which means that the leads will be too, making it easier for them to ground out on the engine.

    Not only that but Ive checked for grounding across various parts of the engine and the engine block has a resistance of 90ohms, not alot, but its 180times more the it should be! (perfect ground is 0.5ohms) ordered a grounding kit but its yet to arrive, seller sent another apparently, but thats not turned up, possibly the snow and stuff, but I doubt it since I bought it on 12th November! Anyway, the point is, check you engine, all the ground leads on mine are oxidised, but the chassis is fine (0.7ohms) its just the engine that isnt ok.

    Hope that helps, J



  • hey si sorry about not gettin back to you.

    i'm sure its its air leakin in behind the vaf. or the vaf itself

    i have a spare dizzy and vaf here.

    a way to check it out is run the car and pull the vaf like stretch the pipe from the vaf to the intake and listen for changes



  • If it is the dizzy I have a complete one for sale, but any of those pipes you have fitted if they let any sort of air in between the sensor and the inlet the cars loses all its power. take the top hose off and check for cracks.

    The bonnet thing, get your car running and then open the bonnet in pitch black you will see blue sparks if you leads are leaking ( i have 2 sets of those for sale too)
    or pull the leads out one at a time and check there are no cracks in the plastic that goes into the engine block, I had one go and that lost a lot of power because you basically lose a cylinder.

    If its none of those then I guess its distributor or sensor



  • If you need the intake pipe I will have mine spare in about 3 days as Ive just bought all the bits for an induction setup



  • you know that 4" pipe from the cat, is that just a straight out pipe or is it with a back box? that could be one of your problems, you want as little back pressure as possible but the wider the pipe the worse the bottom end is, when you in 2nd gear, what kind of revs are we talking as if its a straight out 4" pipe then thats surely waaaaaay bigger than youll ever need, thats like formula 1/truck area!



  • had a good think on this one, hopefully this is right and might help you sort it. Have you set the throttle stop screw, manual says not to, but it is actually really important not to have it so its closed fully, you need a tiny gap, if you dont, then you will wear out the throttle body and have a permanent air leak into the plenum, its also necessary to set the base idle with it, manual says dont tamper, but its an adjustable screw, so its there to be adjusted, only reason they say not to is because the tps would also need to be adjusted to compensate for the new throttle flap adjustment. The AAS is only meant for fine tuning, though it also doesnt require that you adjust the TPS, which the TSS does, so thats why they say adjust it on the AAS because its a lot easier, but the AAS isnt designed to allow the required amount of air through to run the engine properly as the aas circuit is just an idle bypass for the throttle flap, as such the circuit isnt big enough in diamete to supply all the required air, so on engine breaking, ie changing down and the revs coming up due to speed, your plenum will get a massive hike in vacuum, so your brakes should become super powered at the lightest touch, but the engine has no air, causing it to suffocate until you open the throttle flap again, regassing the plenum and dispelling the vacuum, hence the delay and shitiness when it does come back online as the engine will have still been putting in fuel. surprised it didnt backfire!



  • any progress?



  • Hey lads,

    thanks for all the input

    I have been up to eyes in work and Im way for the rest of the week.

    Plan is to first have a look at the air pipe work - look for anything looking straight at me.

    My mechanic reckons its bad leads/dissy, like the lads were saying, is basically shorting in the lower torque bands so we'll have a goo over that

    After that I think we'll look at fuel filter/pump, there is rust on my petrol filler cap so that could be it.

    Just dying to get her back on track again. On the upside fitted HEL braided lines with good high temp fluid which was working well.

    Can someone have a look at my engine bay, link below and confirm that it is a k8. I have receipt for any engine replacement showing something differrent. It makes no real difference to me but would be nice to know exactly what Im dealing with.

    Is there anywhere were I can download the entire manual, anywhere I find it just has it on readable pages, looking to print one out
    cheers



  • your link hasnt worked mate, the manual is in the General discussion top link - FAQ Where to download a manual



  • From pics in your work log, looks just like a 1.8 to me.



  • Thats what Rob said too.

    Makes no odds, just few people said different.

    Cheers


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