Hesitation/Jerkiness/loss of power under acceleration

  • Hi there everybody, I am a newby to UK-MX3.

    I am having the same hesitation misfire problem under acceleration as member mattuhh. I was wondering can anyone give me a step by step guide on how to blank off my EGR valve as I have herd this could be the problem, and is also throwing up code number 29 which is EGR valve vent. I have tried almost everything else I am running out off ideas.


  • Weird, it is un common to have egr problems on a mx, but if its throwing up codes then something could be wrong with it. Although dont see how egr system effects your symptoms.

    Have you tried sparks and new leads, ( common fault due to v6 heat transfer )

    If you can get hold of a dizzy also, id try that. ( common fault again due to heat transfer ).

    Is your ducting from air filer box to manifold tear free?, if it tears you get a air leak which upsets your air flow meter. Have a really good look and pull ducting around.

  • Hi Garfy. Thanks for the quick reply.
    I should have mentioned in my post that the car had a new dizzy & leads just before I bought it. (the previous owner had this problem but changing the dizzy & leads failed to solve it). Also I've carefully checked the ducting on a number of occasions.

    Things I've tried based on what I've read on forums:
    Spark plugs, from Bosch to NGK. This actually made a great difference with the car running faultlessly for about 3 days. However things just returned to normal after this . (The plugs looked their normal colour).

    Other things I've tried are replacing the BAC valve & air flow meter.

    I've also tried disconnecting the exhaust to eliminate CAT. The engine ran just the same.

    Things I've thought about trying include the fuel pump/filter. (I've changed the high pressure filter).

    To sum up, the symptoms the car displays are as follows:

    Engine always starts without problem.
    idle seems ok (when cold),but on warming up displays a slight miss every 40/50 seconds them settles down then repeats slight miss again.

    On moving off, drivability is not too bad, but hesitation/jerkiness becomes more pronounced as engine warms up.

    Not sure which way to go now. Thanks for any further help.

  • sounds perhpas like your over fueling once warm, that would explain why it ran well after new plugs. Are they now quite sooted ??

    Wonder if your o2 sensors on mainifolds are changing resistance once the exhaust is upto temperature.?.

    Theres so many things i could be in honesty, the fact that it does it when warm helps a bit tho.

    I cant see why the fuel pump would play up ??. Usually bullet proof.

    What sort of age and mileage are we looking at?, you think compression is good on all cyl ?

  • Got thinking but have you replaced the egr solonoid valve?, reading below The egr does have an effect under temperature.

    http://www.mx-3.com/manuals/showimg.php?file=/1992 Workshop Manual/F2/92_F2-127.gif

    I cant remember if i have a spare solonoid valve as i stripped my egr system out.

  • i have one here somewhere i think if needs be

  • Found mine, the small plastic pipe onto it has snapped, the egr valve and other solenoid must have gone with the old k8. I've still got canister although its prob of no use.

  • Thanks for the quick replies gents.

    My car is a 1996 with 109k. What I can say is that the car is smooth at high revs if I keep it in the higher rev bands it pulls like a train so I think the compression is good.

    Funny you should mention over fuelling because I had thought of that, but if I just sit in the car and let it warm up on the drive and wait for it to start hesitating/missing, then, if I try to rev the engine it really struggles to get the revs up, but when it finally does and I give it good revving up to about 5000rpm there is a really strong smell of petrol, but not when I am driving.

    I haven't changed the EGR solenoid valve.To be honest I would be looking to strip or blank off the EGR which ever is easier. Would you recommend this? Is it a major job or straight forward? Would be looking to do it tomorrow if its easy enough. Plugs are a light brown colour as they should be.

    I have thought of O2 sensors as well but no error codes are coming up to say there are any faults. Would they even show any faults anyway?

    Cheers Stu

  • This sounds just like the problem I'm having too, only difference is mine always revs fine in neutral and doesn't smell of fuel.
    I still haven't found the cause of my problem, as after I cleared the oil out of the spark plugs they have stayed bone dry.
    Sometimes i hate cars lol

  • Just out of interest are you running any kind of induction kit…??

    or has the air box been disturbed recently....?

  • mines completely stock, put a new air pipe on, but have checked it since and it all seems to be fitted fine.

  • did you run through the throttle body setup me and marco have?

  • the o2 sensors are a pain the arse. Try and pull codes again once warmed up to see if any other codes are there?.

    think stripping out the egr is not a major job. Id try and strip that out first and then see how things are.

    for any parts have a look at probestore.co.uk as a price guide for sensors etc.

  • I am going to have a go at stripping the EGR valve out and going through the throttle body this weekend so wish me luck will keep you posted thanks for the advice gents.

  • did you have any joy on this problem? mine is almost the exact same symptoms. lacks below 5k but after that pulls really hard and smells of petrol. i am guessing the egr valve must have been the issue or you would have told us right?


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