Missfire now won't start

  • Hi to all,

    hoping someone can offer a solution to my problem. I drove the car yesterday on a round trip of 100+ miles in the rain and she didn't miss a beat.
    About 1/2 mile from home she started to missfire. Got home, parked up. When i tried to start her this morning she turned over fine (sounds like it has ignition) but just won't start.

    Would it be likely to be rain water causing a short? Any advice would be greatly appreciated as i can't afford to put it in to a garage.



  • check spark plugs and leads.maybe air filter is damp?

  • I'd guess at distributor, learn how to pull codes in the HOW TO section.

    Check for spark by taking lead out and letting it arc closely onto a valve cover bolt.

  • Marco , edymikis

    thank you for taking time out to offer advice.

    I have checked for a spark and all appears well. Next i moved onto the diagnostics box. The cap doesn't tell me which pin is which so i don't know where to plug in the LED etc to pull the codes.

    Does anyone have a diagram?

    Gaz :(

  • So it tries to start and turns over but won't fire?

    Sound like its trying to fire or not?

    Do you have any immobiliser or alarms installed?

    Got spark on ALL plugs?

    Got fuel pressure?

    Got any signs of anything broken? metalic noises when turn over? belts snapped?

    Did anything happen before the missfire? hit a bump, pothole, drive through water, any overheating, weird noises?

    Whats the inside of the dizzy look like?

    What condition are your leads in?

    Try and turn it over in the dark with someone watching the engine bay without a torch to check for arching.

    Any signs of head gasket failure? oil in water / water in oil?

    Have you flooded it? leave plugs out overnight to let it evaporate off…

  • Hi UKmxadmin

    Sound like its trying to fire or not? A.Sounds like it is trying to fire.

    Do you have any immobiliser or alarms installed? A. Yes but seams fine.

    Got spark on ALL plugs? A. Checked 3 and were OK.

    Got fuel pressure? A. Not sure how to check this?

    Got any signs of anything broken? metalic noises when turn over? belts snapped? A. None broken & no funny noises.

    Did anything happen before the missfire? hit a bump, pothole, drive through water, any overheating, weird noises? A. I was returning from a 80 mile round trip without incident then about 1/2 mile from home it starting to miss fire/loose power briefly. Parked up then wouldn't start next day.

    Whats the inside of the dizzy look like? A. Haven't checked but what should i look for?

    I appreciate your help, thank you.


  • Tried to start the car this afternoon (God it's cold out there) and it fired up and started first turn of the key but died after only a couple of seconds.

    I then tried to pull any fault codes. I wired up the LED and link wire then turned on the ignition. The LED lights up and stays on.

    What does that mean?

    This is driving me round the bend.


  • Odd question, does it have fuel? Both my Mx3's fuel pumps have gone faulty reporting the wrong fuel level on the dash, took me ages to find it the first time, not so much the second thou lol

  • Hi Lori

    i put £25 in before doing the 80 mile journey so i am pretty confident it still has fuel in it.



  • A mate that has Green Flag membership came around and called them out.

    The mechanic turned up and i explained the problem. He attached a booster to the battery as it was partially flat from me trying to start it over the weekend. He turned the key and she fired into life leaving me looking like a right tw*t.

    He revved the car and when done gently it was fine but if he booted it the engine coughed and spluttered and nearly died.
    I drove the car for approx 20 miles and again if i gently rev it and ride the clutch a bit it was OK. The problem occurs when trying to pull out at junctions etc when the engine is under load it tries to die.

    So again i would like to know if this is something someone has experienced?

    The Green flag chap suggested that it was "Over Fueling" but again i'm not sure what that means or how to cure it.

    I would appreciate any help with this.

    Gaz :?

  • Your engine will be running too lean due it pulling more air in through a split rubber air pipe from the air filter box to the TB. Wrap loads of strong duct tape around it and you will find that it will idle fine. Check the pipe for splits, common problem as they are most likely the original and they perish over the years.

    Also take off and clean any breather pipes from the PCV valve on top of the front rocker cover, gummed up one cause running problems.


  • Hi timorridge,

    thanks for that i will have a good check of the air pipe. Can you tell me what you mean by TB?


  • Throttle Body, the 3 pronged fork that sits on top of the engine where the rubber pipe connects. Assuming you have a 1.8 engine?

  • If you don't know how to test fuel pressure then best you don't try and do it. Its starting now anyway so its getting fuel.

    To check dizzy take off the cap and look for any obvious signs of corrosion, burning or wear. Also remove all leads and check contacts for signs of corrosion.

    How does it idle? low/high steady/hunting

    Check all air hoses for signs of a leak, look for cracks, splits, improper seating, has it collapsed or gone soft etc

    Take off air box and VAF and have a good look over the hose going from the VAF to the Throttle body for any splits or cracks.

    Look at the plug going to the VAF for any signs of corrosion.

    Push the VAF cone in very gently and let it slide back out gently, isit smooth? or does it get stuck/jerky? does it slide back out? it should be spring loaded.

    Check that the plastic resonator is fitted properly. (bit that fits to the concertina inlet pipe after the vaf.

    Look at the breather pipes, are they clear or gunked up inside?

    Look at the throttle body, is it clean or dirty inside?

    IF ITS DIRTY it might be worth Looking up how to clean the TB and all bits attached and set them up properly. TPS, Stepper/IAC etc

    Check all the small vacume pipes on the inlet manifold for leaks, remove them all and refit.

    Check all pipes going to the PCV and also to the EGR.

    Thats enough to be getting on with…

  • ukmx3admin

    wow that is a comprehensive list of things to check.

    Looks likely to be a job for the weekend as by the time i get back form work we only have about half an hour of light left.

    I really appreciate all your help and i will keep you updated.

    Gaz :(

  • timorridge

    thanks for your help. I will keep you updated.

    Gaz :?

  • Every thing you have mentioned and experienced gazzoouk
    strikes a chord with my nightmare a year or so ago! (do a search on my posts, the one in the newbie bit) I'm no expert! (as recently discovered/proved) lol But Id take a stab at coil/hall trigger unit in dizzy? coil is quite easy to check with a good meter?
    Unplug the 3pin and 6 pin plugs on dizzy and check the male/dizzy side.
    primary winding resistance should be @20 oC (not today tho!) between the first two pins on the 3 pin dizzy connection (1st is pin closest to ya)
    0.49 - 0.73 ohms ?
    For secondary, (remove dizzy cap to expose coil post) put a meter between pin 1 again and the recently exposed coil post should be 21000 - 31000 ohms
    (21k ohms - 31k ohms dependent on meter range) In these sub zero temps youll prob get lower readings but any readings out of spec maybe point to ya prob?????
    The hall trigger/IG unit is a difficult beast to check? I could find no 'base' meter readings to check against anywhere online etc so took plunge and bought a new unit (UKPS) fitted, sorted straight away
    Pulling codes did not work for me, I had strange 'ghost' codes of '10' '11' '13' etc, I reset ECU, fitted item, vvvrooom! good to go :P
    Not saying for deffo it is that for one moment, but from experience with 2 failed coils and 1 hall/IG unit in 2.5 yrs and virtually mirrored symptoms/issues, worth a check? Hope ya get sorted gazzoouk :o

  • Thanks blackmevyv6

    thats interesting to read. Now i am again going to sound like an idiot but what and where exactly is the hall trigger/IG unit.

    Thanks again


  • Sorry gazoouk, its all in the distributor body! best thing to do to check everything, is remove dizzy cap with leads still attatched (less chance of mixing up) then remove whole dizzy body? (Two 12mm bolts on dizzy mounting flange on side of front cam cover/ cylinder head). also check the 6 posts in dizzy cap and the center carbon brush ( on one of my caps the brush was burnt away! but still ran ok ish!! ) As mentioned before on here, if everything looks ok in cap best leave rest alone in there? coz after removing rotor it all gets a bit complicated under the next circular black cover where the hall trigger/vanes/ig unit live! if ya dont mark everything with a black pen or something it could get messy on re assembly??? :( best do the meter check 1st then dig deeper ? good look hope ya get there :) kev b


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