Possible alternator issue?

Discussion in 'Technical' started by Hellsheep, Mar 22, 2017.

  1. Hellsheep

    Hellsheep Administrator Staff Member

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    I have a ecu talk plugged into the consult port while I'm driving around to monitor a few things etc. I'm having problems with initial rough idle and low idle on cold starts only and also voltage fluctuation between 12-15v according to the ecu talk. The voltage spikes also seem to coincide with a slight misfire/brief rough idle. I've recently done a plenum pull but the symptoms may have been present before it. Wondering if it sounds like the alternator is faulty or something else?
     
  2. rob260

    rob260 Moderator Staff Member

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    Easiest way to check the alternator is to put a volt meter across the battery terminals with the A/C on, headlights on high beam and engine at roughly 1500rpm. It's not uncommon to get some voltage drop with ECU talk so better to check at the battery.
     
  3. Hellsheep

    Hellsheep Administrator Staff Member

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    Cheers will do, what am I aiming for? Around 13?
     
  4. rob260

    rob260 Moderator Staff Member

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    Yeah 13-15v
     
  5. Fists

    Fists Well-Known Member

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    Spiking voltage sounds more like an errant/bad earth than a failure mode of an alternator unless the rectifier is burning through. Check your harnesses and earth straps for solid and clean connections.
    Could also be a coilpack sparking to the plenum, have a look at them while it's running in the dark and see if there's sparks.
     
  6. Hellsheep

    Hellsheep Administrator Staff Member

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    I just wanted to add more information to see if it helps a diagnosis before I've had the chance to test anything further. The voltage fluctuations seem to follow the rough idle/misfire. I'm thinking maybe the misfire is what I should be diagnosing and see if the voltage fluctuations disappear when that's fixed? Is there any harm in swapping TT coils with NA coils? are they the same? I believe I've narrowed it down to Cyl 2 misfire.

    Also the car hesitates when cold at low revs, once it's warm it doesn't hesitate as much. It feels like there is almost no power at low revs on a cold start pulling away out of my driveway.
     
  7. Fists

    Fists Well-Known Member

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    Yeah, that's why I suggested the coilpacks, they can confuse ECUs and stuff. NA and TT coilpacks are the same, there's a few revision by year etc. but all functionally the same.

    I'm assuming you don't have any error codes presenting?
     
  8. Hellsheep

    Hellsheep Administrator Staff Member

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    No codes, I'm going to pull the coils tonight probably and swap with a set of known working ones from my TT project then. While I have them off I may also compression test, with the idle going more normal at temp I'm wondering if maybe this engine has had it.
     
  9. Hellsheep

    Hellsheep Administrator Staff Member

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    Just an update, I ran out of time the other day for any of the work, today I had about an hour so I quickly whipped out the spare coil packs from my TT that were known to be good before I pulled them, also grabbed the AFM from the T-piece on the TT and swapped both coils and AFM to the N/A to see how it went. It seems to be running MUCH better so far, the real test will be on a cold start tomorrow and then also after a day of driving in heat throughout next week at work. It now however idles nicely at lights, doesn't seem to be misfiring anymore and oddly enough I'm now getting reading that aren't 0/0 from the o2's on the ECUTalk....The voltage still fluctuates but it's not too bad, it's between 12.7 and 15 usually, the highest I've seen was 16v very briefly.
     
  10. Fists

    Fists Well-Known Member

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    Good news so far, coils are pretty cheap to stock up on.

    Probably a good idea to check voltages with a multi-meter in case it's getting ready to fry some electrics, check across battery terminals while running and also check voltage and resistance between various earth points; plenum, chassis and battery neg, should be negligible voltage or resistance while running.
     
  11. Hellsheep

    Hellsheep Administrator Staff Member

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    Will definitely do that, just need to grab a multi meter. Could the voltage fluctuation also be due to bad terminal/connection? I do notice occasionally the negative terminal gets loose and needs me to wiggle it to get the car started. It's on my list of items to replace as it's dodgy and I hate having to get out of the car (we all know the trouble of getting in and out of Zed's) just to wiggle a terminal that's loose.

    On the plus side, I have some very good news, my cold starts and rough idle and hesitation is completely gone now that I've done the coil packs and AFM. If I get really excited on the weekend I might replace one coil at a time and see if the misfire comes back to determine what's dodgy and then see if it's the AFM instead. The TT Zed I have is pretty much parts as the engine has a shot head gasket I believe and would probably only suit a rebuild though it's not been driven since it's shot, it's just not gonna run again due to other damage, so spare parts for me it is.
     
  12. Fists

    Fists Well-Known Member

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    Yeah, making/breaking connections definitely causes voltage spikes, that's actually how MOSFETs and other small voltage controllers raise voltage, plus the alternator has a load regulator which will be all over the place with an intermittent load like that. I would move fixing that battery terminal to the top of the list, I used to just live with them too but life is so much better when it's a good connection there, dodgy terminals lead to flat batteries and battery damage over time.

    It is also possible the voltage spiking is only in the wiring to the ECU talk unit w
     
  13. Hellsheep

    Hellsheep Administrator Staff Member

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    Alrighty, thanks for that. I'll get onto fixing the battery terminals up then. I think the main issue I have really is one of them is simply loose due to the battery terminal connector being slightly too big for the battery that's in there. Either way I'll get it sorted.

    On a side note I've had an interesting thing happen today (Fix one thing and more go wrong with these cars)

    I tried to start it at lunch time and the starter was cranking however it took about 8-10 seconds to start, then it ran fine. Almost as if the car was flooded with petrol I guess.

    I noticed while driving around and stopped at lights it seems to be idling around 950-1000rpm today instead of 850ish even with TPS at 0.44v. The Injector reading from my ECUTalk isn't in %, but some other whole number value. Normally at idle it's at 1/1 but idling/letting off the throttle all day today it's at 3/3 almost as fuel is constantly being given to the engine. Wondering if it's also pushing fuel when it turns off/is off. I tried to start the car again only about half hour it first happened and had no issues. When I went to leave work, same thing happened again, took a good 10 seconds to start. Where do I even begin troubleshooting this? Also water temps seem to be much higher today too, struggling to keep it below 85, mostly reaches 90 after a drive with the aircon on. Normally it sits around 79-80.
     
  14. DazzaZ32

    DazzaZ32 Active Member

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    Had this issue, Car wouldnt start when warm, high idle, turned out to be dodgy Coolant sensor connection clean that out, as it cost me a tow home,
    Although a free one through insurance.
     
  15. Hellsheep

    Hellsheep Administrator Staff Member

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    Replaced the coolant temp sensors last night just in case, haven't replaced the connectors but they don't seem to be dodgy, I don't have any other symptoms of sensor failure. The aux fan isn't running all the time, the temps seem normal enough, they've only jumped a few degrees (used to be 79, now sits between 85-90, but it's possible this radiator/cooling system needs a flush)

    I'm wondering if it's something fuel pump related. I think I have a few things to work on before I continue any further troubleshooting of individual problems.

    The AAC, FICD and EGR connectors are all falling to bits and last night I found the FICD connector completely disconnected which was causing high idle. Probably best I replace what I know is faulty and then continue to troubleshoot.
     

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