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'97 ahl 1.6 cam sensor

murran Jun 23, 2012

  1. murran

    murran Registered User

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    not had this a4 long when it started intermittently being down on power lower in the revs.
    i fault code read it when i first got the car (seemed to be running fine) and it had a cam hall sensor fault in it but it cleared and i thought no more about it.

    now its down on power below 3krpm. you can drive around it by not flooring it. like if your holding a constant speed but accelarating by putting just a tiny bit more throttle on. but if you floor it or go too much throttle it seems to drop power in an obvious step kinda way, if you know what i mean?
    above 3k tho its very sprightly, seems to have plenty of grunt on motorways easily holding 80+ uphill.

    with it running you cant clear the "cam hall sensor - no signal" fault. you can clear it without the engine running but start it up and its back again. the engine man light isnt on.
    ive checked the timing and thats fine, the cam sensor has 5v and a ground.

    ive yet to take the car to work to scope it up. if it has got a signal coming out, i'll check the continuity of the signal wire back to the ecu. see if that throws up anything.

    or do you guys think the power problem could be something else? throttle position sensor? map sensor dirty?
     
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  3. Bradderz_1988

    Bradderz_1988 Dont replace it, Upgrade it !!

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    Unplug the sensor, pop a multimeter on the correct pins and pull the fuel pump relay and have some one crank the car whilst you check the sensor for a signal.
     
  4. murran

    murran Registered User

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    right theres a signal coming out and i have coninuity back to the ecu on the signal wire.

    the car is getting progressivly slower and more jerky. but still just the cam sensor fault.
    im thinking that this cam fault has nothing to do with it. think its more an airmass fault, but with the airmass unplugged its near undriveable.

    not had chance to check out the signal voltage on it. guna look into it.
     
  5. murran

    murran Registered User

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    been looking into the signal voltage coming from the airmass.
    its an old style hitachi unit. 12v supply, ground and a signal wire.
    the signal wire at idle is showing 1.3v and when you rev it up the most it reads is 3.3v. that seems low to me given the 12v supply? i would have thought 8v at least?

    anyway i removed it and covered it in carb cleaner and gave the wire mesh a wipe down. on refitting it and revving it up i now am seeing a touch over 4v which is better but it only feels very slightly better on the road.

    think im on the right track. priced up an airmass from gsf............. £117 plus vat!! damn.
     
  6. murran

    murran Registered User

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  7. Bradderz_1988

    Bradderz_1988 Dont replace it, Upgrade it !!

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    Murran your in the trade right just have euro etc send you one try it then if it doesnt cure it send it back saying its the wrong one and et your cash back or have them credit your trade account. Its what i would do rather than trust someone on ebays word for it on a second hand unit.
     
  8. aragorn

    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    revving it in neutral wont see anywhere near the full range of voltages on the MAF sensor. You need load on the motor, and that means driving it.
     
  9. murran

    murran Registered User

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    from reading up at work on esi from the bosch kts650 today, i should be seeing atleast 6v from bursts of throttle when stationary.

    what it reads while driving i dunno? could try and run the multimeter in the car? or gaffer tape it to the windscreen? lol. could do with taking it to work so i can plug the diagnostics in and drive it tbh but our lass is always using it.

    might be cheeky and pop into gsf, i know them very well at the sheffield branch. see if they'll let me borrow one off the shelf hahahaha. i'll ring danny up in the morning and ask him nicely.
     
  10. murran

    murran Registered User

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    well the chap on ebay has said if the airmass he's selling is no good then he'll refund. guna have a go at that i think.

    i got a "no" at gsf! lol.
     
  11. murran

    murran Registered User

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    the second hand airmass came thru the post today. fitted it just now as it was going dark. been for a spin in it and its much better. pulls from low revs and doesnt bog down like it did.

    guna check the signal voltage tomorrow. but atm i think thats £20 well spent.
     
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  13. aragorn

    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    good stuff :)
     
  14. murran

    murran Registered User

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    well idle is showing around 1.6v so not that much different there... but can get to read up to 5.6/5.7v revving it up when stationary.

    car still doesnt feel fast in the slightest. but then being a 1.6 pulling around a big chuck of car its never going to be, any car with under 100bhp per ton id class as officially underpowered! but then i knew that when i bought it and i'll stop complaining it now!
     

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