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Motors Unexplained Breakdowns, Any advice?

Discussion in 'General' started by DeadP1xels, 11 Oct 2011.

  1. DeadP1xels

    DeadP1xels Music Enthusiast

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    Just noticed this i see where your coming from but im pretty confident on two seperate occasions these guys have helped me out completely out of there own way there very busy but still fit it in so its good for me and then don't charge for callout

    + There a family business who have built themselves up from having a good reputation locally
     
  2. Amon

    Amon inch-perfect

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    Bear in mind that there can be several causes for your symptoms and nobody can ever make an appropriate and acceptable diagnosis without inspecting the vehicle in person. Now, I'll break this down into generalised sections for easy understanding, each with bulleted possible causes and each of those subpoints will describe ways to diagnose correctly. The sections are in no particular order, however, whoever that is diagnosing the problem must always start with the basics: air-fuel-spark. Plugging in a scan tool is no substitute and, if I may add, it is breeding an entire generation of ill-suited technicians. That's why there is no longer such a thing as a mechanic... they are all just parts replacers and scan tool readers.

    Fuel
    The fueling system is one of the few circuits that is not monitored by the car's OBD-II computer. Because of this, faults in this system will never trigger a diagnostic trouble code (DTC) to the computer, although other driveability issues will ensue downstream from these issues and, in turn, trigger their own seperate DTC.
    • Have you ever changed your fuel filter? It could be getting clogged up. The next time the car bogs out, give your fuel tank a real good booting to shake any foreign matter from the filter medium. They can never be inspected properly until the tank is emptied and then dropped out from the car to be opened up. The correct way a tech is supposed to diagnose a clogged filter is to let the fuel line fill a metered flask and calculate the flow rate of the fuel pour. Low flow indicates a bad pump or filter, which are one assembly in the tank.
    • A disabled fuel pump circuit can cause no-start situations. Possible causes are dead relays, bad grounds, open/shorted circuits, or simply a dead fuel pump. Proper diagnosis involves using a multimeter to test the circuit at key-on and engine-start situations and monitoring circuit voltages.
    • Ensure your fuel pump regulator vacuum line is secured. A broken or disconnected line will cause poor fuel pressure and a vacuum leak at the same time.

    Intake
    Some of your symptoms lead me to think that you might have something highly restrictive in your intake system. Another possibility is your engine is breathing in unmetered air.
    • Check your air filter; it may be incredibly clogged. Maybe a rag or something bigger is stuck in the MAF or AFM sensor if present.
    • Remove the intake hose to the throttle body and inspect for cracks, rips, and disconnected vacuum lines. Unmetered vacuum leaks, if big enough, can prevent an engine from starting and will definitely cause terribly rough idling. This should definitely be looked at if your car runs on a mass-airflow or airflow-meter sensor.
    • Unlikely, but, your idle speed solenoid (or "idle air control") may be sticking shut and not allowing the car to breathe when starting and idling. You'd know it's defective if you can start with your foot on the throttle.

    Exhaust
    An engine that is unable to exhale will cause driveability issues.
    • Have you ever triggered an engine light recently? It's possible that your catalytic convertor could have blown to shreds or disintegrated and the mangled remains are now causing extreme exhaust backpressure. You can do a basic, but unreliable, check by feeling the gases coming out of the exhaust tip under revs. The correct and acceptable diagnosis by a technician involves using a pyrometer for pre- and post-cat readings.

    Ignition
    Your ignition is timed by either your crank position sensor, cam position sensor, or both.
    • Inspect and resistance check your ignition wires. Old and damaged wires can cause high resistance, leading to improper spark in the cylinder, causing misfires.
    • If the above turns out okay, check the coils and/or distributor. I know distributors will carbon up by design, but coils will go out over time and from all the heat soaking.
    • If you want to go through the process of removing your spark plugs, you can check the spark quality by grounding the electrode to your cylinder head or intake manifold (high resistance to battery ground for safety).
    • Check your ignition timing. I doubt that you've done something to faff it up from it's factory setting-- because it is an involved process-- but incorrect timing will cause symptoms that perfectly match your own.

    Last resort
    These are more complicated, technically-inclined procedures that you'd look into only after you've exhaust all the elementary diagnostics.
    • ECU reflash with updated firmware.
    • Valve timing inspection.
    • Injector pulse width and flow testing.
    • Oxygen sensor diagnostics; verify correct switching rates and voltages.
    • Engine harness inspection. Ignition, injector, and sensor inputs may not coming in and out of the ECU as they should. Involves diagnosing with a voltmeter (not "suspecting") your crank or cam position sensor and its wiring.
    • Throttle position sensor and MAF, AFM, and MAP sensors could be giving the ECU erroneous readings. Depending on the vehicle, it can cause no-starts and poor idle.
    • Valvetrain inspection. Some valves may be sticking open or are carboned up, preventing correct cylinder compression. Compression tester or a leakdown tester is needed to know for sure without taking the cylinder head off.
    I don't really have the time or patience to go further, but I dearly hope your mechanic (technician) is not ignoring diagnostic fundamentals purposely.
     
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  3. Xir

    Xir Well-Known Member

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    You're right, but been the guy that used to write the handbook for (one of the) scan tools. :D (in a previous, very short, career) I#ve got to defend them.
    Most mechanics are using it wrong. The scan tool CAN do a lot more than read-out the errorcodes and teach keys.
    I dare to say 90% (probably more) are never used for more though. They are actually diagnosis tools, you can find almost every error with it, but you have to know what you're doing, know how to diagnose, and take your time.

    Problem is...sitting there tapping the scan tool isn't seen as "Working on the car" by many bosses and customers.
    Wielding a wrench replacing something...anything is seen as repairing. :duh:
    While without a proper diagnosis this may be futile.

    Honda actually holds classes for their mechanics to learn this...diagnosis along the air-fuel-spark line WITH their scan tool. And it works this way. You can check and test every signal line, every solenoid, every sensor. Then you know what too look for.
     
  4. DeadP1xels

    DeadP1xels Music Enthusiast

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    +rep for this!!

    Not got enough time to read it now but i will read through it later :)

    Im going to wait till next week unless they call me first if they don't do anything it will probebly end up on my street till my dad gets back so we can take it out and i have some help to actually get it back.....

    All these issues are stressing me out though, i could'nt sleep last night and ended up finally falling off about 4am then woke up realizing i had slept through college.

    Atm my week consists of being late for college because my car breaking down not concentrating wondering why the **** my car is being a bitch

    going to a job i hate to pay to fix the car thats transporting me to the job i hate thats still not actually fixing it.... so im pushing the car im paying to fix with the job i hate :wallbash: BAH BUMHUG!
     
  5. Prometheus

    Prometheus New Member

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    This is slightly random and just an idea, but do you ever get a hissing/ rushing air sound when you open the filler neck to put fuel in?

    A couple of years ago my car was doing the same thing (not a corsa but I'm assuming they all have a similar system), just randomly cutting out as if it was running out of fuel even when I knew there was plenty in the tank.

    I eventually traced the fault to a broken solenoid that at certain pre set parameters opened and allowed the vacuum of the engine to suck the fuel vapours from the tank. when the solenoid broke it was basically allowing the engine to suck all of the air out of the fuel tank and the fuel pump couldn't cope and so the engine stopped due to lack of fuel.

    Leave it 30mins to an hour for the tank to return to normal pressure and it would start and run again no problem.

    I'm not saying that is what is wrong with yours but it could be something just as obscure and random.
     
  6. Krikkit

    Krikkit All glory to the hypnotoad! Super Moderator

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    I often used to get that in my old Fiat, and that never struggled for fuel. Rarely happens with my current car, but that's running a modified tank breather setup to get rid of the fume recirculating jobby.
     
  7. padrejones2001

    padrejones2001 Puppy Love

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    Sounds a little similar to my old car. It would idle very coarse immediately after turning it on (if it started at all) and again when coming to a stop, many times resulting in a stall. In the end, after beating our heads against the wall, it ended up being the fuel system, specifically a bad fuel sending unit and a loose fuel rail.
     
  8. DeadP1xels

    DeadP1xels Music Enthusiast

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    Thats what im thinking it is....

    From a noob point of viiew this is what my brain is telling me.

    The car has never stopped in high gear or at any fast speed either stopped or idling has it broken down.

    Now as i said yesterday the car broke down and i could not get it going but after a while it started to kick back into action and you could feel rumbles as you turned the key.

    Eventually the car started but would idle heavy till stall, i decided to stop there because i needed to make it clear to the mechanics that the problem was still there so he could see, however i have no doubt in my mind that the car would have started if i carried on going. (they started it as i walked away)

    So initially i was thinking the car was choking on dirty fuel/Not getting enough

    The mechanic has told me there is a small split in the fuel tank but would'nt effect it they did think it was the fuel pump but between picking it up on the third breakdown and giving it back to me 4 days after they must have decided infact it was'nt the pump whether that was because they did'nt want to charge me more incase it was wrong i have no idea.

    The car is not stopping dead and not moving again which obviously tells me that something is loose or not working all the time everytime its stopped "except the first" its gone again so maybe its another sensor? im not sure its very frustrating
     
  9. Blarte

    Blarte Moderate Modder

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    Give the Distributor cap a good inspection ... had a metro GTA once (don't mock me) Did exactly the same thing as yours in HOT or Cold weather .. in wet weather I would Kangeroo ..
    Anyhow turns out crack in cap ..
    It may be that simple
     
  10. Krikkit

    Krikkit All glory to the hypnotoad! Super Moderator

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    No dizzy on these cars, coilpack only.
     
  11. Blarte

    Blarte Moderate Modder

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  12. mvagusta

    mvagusta Did a skid that went for two weeks.

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    Fair enough, but don't forget the other stuff I posted!

    I think you need new mechanics, unless you're happy for these problems to go on for who knows how much longer? Weeks? Months?

    A mechanic's job used to be much easier, now there's electrical and electronic equipment all over the place, it's often a pita just to change a spark plug these days, where once upon a time it could and was done with a beer in one hand. Sure any numnuts can do a basic service, but I think it's about time your car was serviced by an expert.

    If we're all going to start posting explanations of how to diagnose what the problem might be, then this will become a very long thread...
     
  13. outlawaol

    outlawaol Geeked since 1982

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    I had an old '89 Buick lesabre that had nearly the identical problems as listed here. It turned over and ran ok in cold weather and rainy weather. At one point it would not run right, took it to the garage and it turned out to be that coil pack.

    It could be that, but who knows. Its worth checking I guess! :)

    Also I am so glad my Honda has a cap/rotor - its so cheap to fix and it lasts forever!
     
  14. Krikkit

    Krikkit All glory to the hypnotoad! Super Moderator

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    I already suggested checking the coilpack, they can fail quite readily from heatsoak. The ones on my car are exactly the same - they're directly on the rocker cover drooping down to the spark gap, so they suffer immensely.

    Wild stab in the dark for these kinds of problems half the time. :)
     
  15. IanW

    IanW Grumpy Old Git

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    This often helps (well it makes me feel better!

    [​IMG]
     
  16. DeadP1xels

    DeadP1xels Music Enthusiast

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    Seriously i have come to this....

    After the forth time i felt like standing on the bonnet and launching my foot into the windscreen

    Oh well i have decided not to call the garage till they call me with a solution of sorts even if its "we have no ****ing clue"
     
  17. wiby645

    wiby645 Member

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    ive had exactly the same problem with my car before (saab 9-5)
    my problem was the crank position sensor, and iirc saab and vauxhaull crank sensors are the same.
    i feel your pain, cars with unknown problems and mechanics who cant fix it, its very fustrating.
     
  18. Teelzebub

    Teelzebub Up yours GOD,Whats best served cold

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  19. DeadP1xels

    DeadP1xels Music Enthusiast

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    called the garage

    The fuel tank as said before had a split in it and when filled to the top it was leaking fuel they also said there was some rust in there and was probably getting in the fuel

    They have replaced the tank and fuel send unit with a second hand one from the scrappy

    I really hope this is the problem because i might just set it on fire if it breaks down again.
     
  20. Krikkit

    Krikkit All glory to the hypnotoad! Super Moderator

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    If it doesn't work get the crank sensor changed - they're £20 on eBay, and if it makes no difference you can sell it on. :)

    Good to get your tank and sender sorted if it's been leaking and getting contaminated with road debris.
     

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