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 Posted: Tue Apr 24, 2012 5:28 am |
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Joined: Apr 15, 2012
Posts: 23
Trade Rating: 0
Location: uk
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Blue skies today so up early and on with it.
Map sensor.- idle 1.25v blipping 4.8v moves around a bit with idle speed but in lag so I think in responce to and not causing the problem.
TPS.- throttle closed .8v open 4.8v constantly .8v at idle
Idler control valve.- cleaned again, stepper motor coils both measured at 50 ohm.
Crank sensor.- coil 300 ohms. good waveform.
Purge valve.- removed and blocked for the moment. coil 38 ohms.
Engine temp sensor.- aprox 3k with cold engine aprox 200 ohms hot
Lambda sensor.- Top 2 wires in the connector seem to be the heater. (measures 18 ohms.)
Bottom 2 wires waveform 0.1v to 1v
Now fed up, don't think I'm seeing any conclusive fault indications, I'm going to spend an hour tidying up the earth strapping then give it some more thought.
Bill.
Added as an edit. Idle and everything is perfect for the first several minutes from cold, its always the same, (nothing random about it ) can someone confirm that the system starts in open loop then goes to closed loop when warm?
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Posted: Tue Apr 24, 2012 1:25 pm |
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Joined: Aug 01, 2011
Posts: 390
Trade Rating: 0
Location: Bath UK
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Hi Bill
Yes they start up in open loop as lambda sensor takes a little while to warm up then it will enter closed loop if the engine temp is hot enough
Your sensor readings look good.
Could really do with scanning for stored fault codes and watching parameters as engine warms up from cold
If you don't have the means to clear fault codes then you could disconnect the battery overnight and then reconnect it and let it relearn the best settings anew for itself in the morning. If you've had a poor battery earth then it may have adjusted to wrong voltages from the sensors so getting the ECU to take a fresh look would be good. You'd most likely need to re enter your radio code so make sure you have it
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Posted: Tue Apr 24, 2012 4:09 pm |
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Joined: Apr 15, 2012
Posts: 23
Trade Rating: 0
Location: uk
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Hi Deckchair5,
well it's running ok now but not solved in the positive way I was looking for. Originaly I had temporarily connected an additional earth strap from the battery to one of the top suspension bolts, this improved the cranking speed considerably. Today I made that permanent with a new battery terminal connector and a proper soldered on eyelet at the suspension bolt end. I also renewed the original earth strap to the gearbox . The battery neg was disconnected for about 90 mins so the stored parameters may have been lost. Then clutching at straws and acting on the advice of a friend (he works at our local garage) I removed the new spark plugs to check the gap, he had suggested closing them to the minimum I felt comfortable with which he said had worked for him in the past and is what I did. Since then it has run fine, I know I should be happy but on reflection I didn't try it after the wiring tidy up and in light of the advice in your last post the possible unintentional reset . If indeed its the plug re-gapping that has fixed it I cant help feeling it may be masking something else rather than an actual cure. I guess my best bet is to run it for a few days and see what happens. Give me a big dumb diesel engine anyday, lol.
Once again thank you for your advice and help.
Bill.
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Posted: Thu Apr 26, 2012 4:19 am |
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Joined: Apr 15, 2012
Posts: 23
Trade Rating: 0
Location: uk
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It's still running absolutely perfectly. The plugs are now back to bog standard gap and it's made no difference so that was not the answer. I can only assume that the cleaning, attention and disturbance I gave everything resolved the issue but a reset and new ecu learning was needed to bring operation back to normal. No matter what I have learned a great deal about 206's and I will feel much more comfortable dealing with any future problems.
Thanks to everyone and special thanks to Deckchair5.
Bill.
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Posted: Thu Apr 26, 2012 5:11 am |
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Joined: Aug 01, 2011
Posts: 390
Trade Rating: 0
Location: Bath UK
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Hi Bill
Glad it's running better. You can really chase your tail trying to determine which of the many sensors that affect tickover may be affecting things. I'm glad you have your plugs back to normal gap as reducing the gap from recommended should never really help things and would constantly be on my mind if anything happened in the future as there would always be that unknown of whether that is affecting things
Most likely the ECU reset and subsequent relearn made all the difference as the ECU had been experiencing wrong voltages from all sensors for some time with your poor battery earth
Good tip- voltage drop test
Compare voltage drop with engine running between your battery earth connection and a shiny metal earth on the engine. Sounds weird I know but you're checking earth cable integrity and looking for near 0v of course where anything above 0.5v would pinpoint a poor battery earth connection straight away. The root of many evils 
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Posted: Thu Apr 26, 2012 6:26 am |
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Joined: Apr 15, 2012
Posts: 23
Trade Rating: 0
Location: uk
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Hi Deckchair5,
Earth strap was frayed through about 75% right where it attaches to the engine/box, wasn't showing any voltage drop or difference when running but a sizeable 2v drop (neg terminal to engine) when cranking. Could it be that the repeated extra cranking 'dip' had corrupted the memory? Anyway been changed now plus the extra strap so well 'over
engineered'.
Thank you once again for your help.
Bill.
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