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[Mal]

Here goes.........well the engine light has been coming off and on for a while now.   It appears for a few seconds then goes straight out while i'm driving. Happens ever say 50 odd miles so I have sort have let it go as she has been running fine anyway.

Tody though after stopping ( Then shopping ) I tried to start her and she just spun round really quickly on the turn of the key. No firing. Tried it a few times then gave her a pedal full of gas and it started. Happened again on the way home when the wife wanted to stop somewhere else.

Just checked the codes...engine not running and there is a 31 dispalyed. Is this me Crank sensor again as I only replaced it this time last year

The other codes present are:
89
13
73

and of course the 31

 

[aaronjb]

31 is normal if the engine isn't running - with the engine running that code should disappear (if it doesn't then yes it indicates a problem)

I suspect your problem lies elsewhere, though:
13   O2 Sensor 1 Open Circuit
89   O2 Sensor 2 Open Circuit
73   Mass Air Flow Sensor Voltage Low

I wonder if these circuits share a common fuse or earth point?

[Mal]

Wouldn't know on that.

But I will check codes again with the engine running

I hope it's a simple fix as a loose earth or fuse. Don't fancy spending out on expensive parts this time of year

[Mal]

Happy Days.

Paper clip test with the engine running......no 31 so that's a bonus

So I am left with the

89
13
73

Any connection with the 3 or are they all seperate faults.

[Kevin Wood]

Hmm. both Lambda sensors and the MAF. Sounds like something has thrown the fuelling out on both banks.

Is it getting up to temperature OK?

Are symptoms and worse when cold or hot?

When it plays up, try unplugging the MAF sensor and see if it'll start and run better without it.

Does it drive OK once it's started?

Kevin

[Mal]

Ah Kevin sounds like its a job for your Tech 2 

Car gets up to temp fine.
Car runs fine.
Tickover is Fine.

I will try unplugging the MAF Next time she plays up.

That's why I have never been bothered about the intermittant EML. Until today when she wouldn't start unless I gave her a throttle full on the accellerator pedal.

It starts fine now though

[aaronjb]

Hmm. both Lambda sensors and the MAF. Sounds like something has thrown the fuelling out on both banks.

Is it getting up to temperature OK?

Are symptoms and worse when cold or hot?

When it plays up, try unplugging the MAF sensor and see if it'll start and run better without it.

Does it drive OK once it's started?

That would just give you a 'low/high' error on the Lambda sensors though, wouldn't it, rather than an open circuit error?

Actually.. does the open circuit refer to the heater circuit or to the signal circuit, do you know?

[Mal]

Anyone else have any ideas. 

[Kevin Wood]

Heater circuit is not monitored on the Motronic 2.8.1 setups.

It can't check for an open circuit per se, so I'm guessing it's just seeing 0v or no activity from the Lambdas. The fact that it's both sensors makes me think it's something common to both banks rather than both having failed. 

Kevin

[aaronjb]

I bow to your superior knowledge, Kevin

In that case, perhaps a really, really lean mixture event? Lean enough could cause the sensors to read ~0V and a post-MAF air leak somewhere could cause the MAF to register an unfeasibly low voltage at the same time..

Having said that, I suppose there is no way of knowing if these codes are related to the non-starting event (which I'm guessing is what Mal is actually worried about) or related to the light flicking on every now and then during normal running.. not without hooking it up and viewing live data, anyway :-/

[Mal]

It's time to get it on a Tech 2.

Pm has been sent to Kev