Misfiring - Advice needed

Discussion in 'Tech/Mech General' started by TerryL, Jun 29, 2016.

  1. TerryL

    TerryL Funster

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    Following on from the thread about "thrashing" the engine periodically I've got an intermittent problem that I think may be related. I'm not a "thrasher" but like to give the engine a workout every now and again. X250 07 Ducato 2.3 Multijet with 75000 miles.

    But we've just done a lot of miles (I'm talking thousands here) in Scandinavia and frankly the roads are not up to giving the motor the 10 min workout proscribed. In fact I've rarely got it above 50mph and tend to stick around 2000 rpm in 6th. But every now and again, particularly if I've just used a high power setting to, say, climb a long hill, the engine suddenly starts misfiring and hiccupping (that's what it sounds like) under "normal" cruising loads. After a few minutes it settles down but the engine management warning light comes on (my ODB reader says Throttle Actuator Control Range / Performance Bank 1) and we go into limp mode. I've discovered that I can "clear" the misfiring by giving it full throttle for around 10 secs, but the light stays on until 5 restarts when it goes out. It seems to come out of limp mode after a 5 min stop.

    My point - is there enough crap generated in the cleaning process that could cause this misfire? Or should I be looking for a dealer?

    Interestingly, over the past 2 days I've been doing some higher speed motorway cruising and the fault hasn't re-appeared.
     
  2. Boringfrog

    Boringfrog Funster

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    "Full throttle for 10 seconds" while stationary or driving? Either way I wouldn't do it.
     
  3. andy63

    andy63 Funster

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    Could well be just your throttle control as your fault code reader is indicating... usually two potentiometers that cross reference with each other and indicate to ecu the speed of throttle operation and how much.. If one was faulty it may give the eratic running described over part of the range...
    Andy.
     
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  4. Stealaway

    Stealaway Funster

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    Any reason why?
     
  5. TerryL

    TerryL Funster

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    Sorry should have said while driving. Did stop during one of the episodes and try revving to 3000 rpm whilst stationary - still misfired but with smell of unburned diesel and didn't cure it.
     
  6. WillH

    WillH Funster

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    Could be injectors or, if you are getting black exhaust, air filter.
     
  7. PP Bear

    PP Bear Funster Life Member

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    All the same symptoms for me, had no4 injector diagnosed, but I knew it wasn't that. Gave me the right run around for weeks. I extended the loom as some forums suggested it might have been too short, cleaned all connectors etc. It was intermittent and really hard to pin down. Checked the throttle actuator and was working find.

    Ended up finding the turbo dump/boost was sticking. So drove up on my levelling ramps and had someone rev the engine while I watched to see if it was working properly and it wasn't moving at all. Freed it off with an adjustable spanner and lubed with some spray and it was like driving a new vehicle.

    Might not be the same with you, but that was my experience after having the same symptoms. Even my mot tester had commented on the misfire, but now all gone and a quick fix as well :)
     
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  8. TerryL

    TerryL Funster

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    Thanks PPBear, sounds a good possibility. Will have a look when I can get the van onto some firm ground.
     
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  9. TerryL

    TerryL Funster

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    Further - yep that's the problem but I haven't been able to free it off. I can live with it until I get it to my local garage.

    Thanks once again - knew I'd get the answer here.
     
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  10. Scattycat

    Scattycat Funster

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    Afriend has just had a similar problem with his car.
    It turns out that one of the injectors had come lose.
     
  11. TerryL

    TerryL Funster

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    Thanks Scattycat but I'm fairly sure that's not the problem here. But I'll get garage man to check it anyway.
     
  12. elamessa

    elamessa Funster

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    Egr valve sticking?
     
  13. TerryL

    TerryL Funster

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    I know it's been some while now but I've finally got to the bottom of this and thought my experiences might be helpful to others.

    Got the van home okay and took it to my usually excellent local garage who, despite not normally handling larger vehicles (can't get them into the workshop), offered to sort it out. I pointed out what I thought and had been suggested was the problem, and after reading lots of advice on the forum also mentioned that there was a history of throttle body failures. When they rang the following day to say it was all fixed the head honcho said "no, you don't have a turbo relief valve, we've checked the throttle body and it looks okay. The problem was the EGR, so we've blanked it off. It's running fine now". So I paid him and took it home the "pretty way" to give it a proper run. Yes you've guessed, I only got a mile along the road............... Admittedly it was a lot better but still not right. Went straight back and after a discussion we agreed that I should run it for a while to see if what they'd done would clear the system with a bit of use. Hmmmm! But having planned to go to Malvern I agreed.

    And it was better, but the Malvern trip did not clear the fault so back to the garage. This time he suggested a Terraclean, where a chemical process was used to thoroughly clean the engine, so that was booked in. £120 later although the motor appeared to run more smoothly and quieter, the misfiring still occurred. I understandably lost confidence but took it to Lincoln anyway, just to check.

    Once upon a time I used to do all my own maintenance but computerisation has put a stop to that and of physically I'm not now agile enough to do much more than check the oil etc. Re-reading all the various threads convinced me to bite the bullet and take it to the local (well 25 miles away) Fiat Commercial dealer, armed with a detailed account of the symptoms and what had already been tried. My philosophy was that I could take it to a variety of garages "who knew what was wrong" and end up spending a fortune replacing the wrong bits. I was already £200 down!

    A very knowledgeable service receptionist carefully read through my prepared notes and said he was pretty sure it was the throttle body, giving me a thorough and reasoned explanation, including the history. We booked a date when he would put it straight onto the analyser to prove it then get it fixed. Unfortunately the analyser was being updated when I took the van in but, not needing it for a while, he took it in anyway and promised to let me know their findings. It took a few days before they had a proper look, but they actually found three problems: the exhaust front pipe into the cat was leaking and had been for a while; the EGR had not been "blanked off" but rerouted involving the brake servo (!!!), and there was corrosion around the throttle body and it's wiring harness. It took somewhat longer to get a new throttle body as Fiat had modified it following the water-over-the-scuttle debacle some years ago. It was this water overflow onto the throttle body that caused the main problem - at that time a reseal and plastic shield was an approved Fiat mod and a warranty replacement if the customer asked for it! As it wasn't safety related it was not a product recall. Incidentally all the info I've read mentioned throttle body problems but as far as I can remember none actually explained why. Well now you know.

    They fixed the exhaust leak, fortunately just a realignment, resealed the scuttle, checked the EGR operation and replaced the throttle body. I picked it up this morning and (after refilling the fuel tank they'd emptied test driving it) took it for a run. I could not reproduce the fault and it performed beautifully so we'll try a trip to Blackpool next week to prove it.

    A couple of recommendations then for owners of earlier model Sevel X250's. If your vehicle hasn't had the engine cover mod carried out it's quite possible you will suffer this problem. As a first check, examine the wiring harness underneath the throttle body for corrosion - that in itself could have been the cause of the fault. I was lucky the harness didn't need replacing (my man mentioned £200!!!) but it's worth a good look. Then either get the cover - you'll have to pay for it and it might no longer be available, the dealer couldn't put their hands on one for me - or maybe find one at a vehicle breaker.

    Sorry to be so long-winded but I've always felt that someone is bound to benefit from anothers experiences.
     
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  14. TerryL

    TerryL Funster

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    Sorry, double post.
     
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