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Engine check light back on.................AGAIN


Lord-lupo
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Hiya folks

       Shortly after I bought (private) my 02 plated 1.4 Lupo the engine check light came on, I planned on doing a service anyway, plugs, oil, filter and air filter which was carried out, I also purchased a fault code reader to obviously read and clear fault codes.

  I read the codes before I cleared them but now the lights back on, the codes are as follows...........

P1151 long term fuel trim additive air bank 1:range 1: system to lean

P0402 EGR system:excessive flow

        I have now idea where to start looking or changing (I'm used to carbs, points and rotor arm ignition not these electronic things) 

 So any pointers as to where to start looking or bits to change, the car still runs perfectly well..............................at the moment 😁

 

  Thanks LL 😛

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The error messages lead me to suspect an air leak. The fuel and ignition systems are both fine else you'd get other codes. Sensors are most likely fine too. It is possible that O2 is out but unlikely as they are very tough, and unusual to fail in normal use.

The ECU has analysed the exhaust gas and has tried to get the mixture just right by adjusting the throttle and fuel injection pulses and has basically reached end stop. As in, either it can't close the throttle any more (to reduce air) or is adding more fuel to the point where the idle revs start creeping up (above about 900). So to keep the idle stable together with a decent exhaust gas mixture (meaning the fuel / air mix), it has had to reduce fuel, resulting in a lean mix. This can be caused by excessive exhaust "air" from the EGR valve being stuck (unlikely, but possible), or most likely air being sucked in from some other tiny gap. It doesn't take much which is why it can be a pain to fix. Put it this way, a gap the size of the edge of a little finger nail is enough. Sometimes you can hear the air whistling in... there is a way to use raw propane gas from a flexi hose in your engine bay to see if the idle revs change when you get near the leak- they go up.

Also possible are - low fuel pressure (filter, pump, pressure regulating valve), but unlikely. TPS,  or throttle valve misbehaving, giving wrong readings to ECU.

my guess is that the car drives completely normally otherwise....?

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37 minutes ago, mk2 said:

The error messages lead me to suspect an air leak. The fuel and ignition systems are both fine else you'd get other codes. Sensors are most likely fine too. It is possible that O2 is out but unlikely as they are very tough, and unusual to fail in normal use.

The ECU has analysed the exhaust gas and has tried to get the mixture just right by adjusting the throttle and fuel injection pulses and has basically reached end stop. As in, either it can't close the throttle any more (to reduce air) or is adding more fuel to the point where the idle revs start creeping up (above about 900). So to keep the idle stable together with a decent exhaust gas mixture (meaning the fuel / air mix), it has had to reduce fuel, resulting in a lean mix. This can be caused by excessive exhaust "air" from the EGR valve being stuck (unlikely, but possible), or most likely air being sucked in from some other tiny gap. It doesn't take much which is why it can be a pain to fix. Put it this way, a gap the size of the edge of a little finger nail is enough. Sometimes you can hear the air whistling in... there is a way to use raw propane gas from a flexi hose in your engine bay to see if the idle revs change when you get near the leak- they go up.

Also possible are - low fuel pressure (filter, pump, pressure regulating valve), but unlikely. TPS,  or throttle valve misbehaving, giving wrong readings to ECU.

my guess is that the car drives completely normally otherwise....?

 

 OMG I had to ask didn't so many options too, with the links below I notice the exhaust my be the cause too, the exhaust is a bit shagged, can't here it blowing but is suffering from the old tin worm so I need to replace that at some stage, so might be one option to test out, but can't hear any whistling that would lead to an air leak.  

36 minutes ago, Sausage said:

EGR valve is stuck open most likely, take it off and clean it.

http://wiki.ross-tech.com/wiki/index.php/17559/P1151/004433

http://wiki.ross-tech.com/wiki/index.php/16786/P0402/001026

Do egr first and see if the other fault is still there after a bit.

 As above the exhaust needs doing, from fanimold to the back of the car, so may do that sooner rather than later and see if that helps

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I think it has something to do with the lambda sensor aka emissions 

I used to drive below 60mph all day and the engine light turned on several times. To fix that you can just go pedal to the metal for a couple of miles, let the engine and all systems cool down, restart the car and the light should go off

 

Note: Can you tell me which OBD adapter did you use? Mine is giving me error connecting to ECU. It could be the adapter or aftermarket radio 

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On 5/8/2019 at 12:09 PM, GasWeedorAss said:

I think it has something to do with the lambda sensor aka emissions 

I used to drive below 60mph all day and the engine light turned on several times. To fix that you can just go pedal to the metal for a couple of miles, let the engine and all systems cool down, restart the car and the light should go off

 

Note: Can you tell me which OBD adapter did you use? Mine is giving me error connecting to ECU. It could be the adapter or aftermarket radio

 

    That's seems to be an easy try to fix issue, will try that first, here is an ebay link to the one similar to the one I bought, mine was removed by ebay for some reason but I'm sure this is the same model https://www.ebay.co.uk/itm/VS450-OBDII-VAG-Code-Reader-Diagnostic-Scanner-Com-Reset-Airbag-Tool-For-Audi-VW/401752240667?epid=1786741465&hash=item5d8a4cb21b:g:jXYAAOSwAHtaJ8iz

   

 

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On 5/6/2019 at 8:51 AM, Sausage said:

EGR valve is stuck open most likely, take it off and clean it.

http://wiki.ross-tech.com/wiki/index.php/17559/P1151/004433

http://wiki.ross-tech.com/wiki/index.php/16786/P0402/001026

Do egr first and see if the other fault is still there after a bit.

  Dumb question I know Sausage but where would I find the EGR valve? 

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On 5/12/2019 at 9:02 AM, Sausage said:

At the front right hand corner of the engine.

386734_10151384747670450_1982767588_n_zp

Thanks for the picture Sausage, will take a look over the weekend and give it a good clean 😉

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  As haynes don't do a lupo manual I've just ordered a polo one as the mrs has the polo, should come in handy for mine too hopefully.

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One more question, the egr valve has a small metal tube coming out of it which I think is something to do with the vacuum, the 1.4 polo we have has the same egr valve on it as my lupo, on the tube is like some kind of small breather or plug, mine is missing of the lupo does it matter its not there? 

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Not sure which tube you mean, but if it's what I think, it's the vacuum supply that pulls the EGR open. Solenoid controls the vacuum, which in turn varies the pressure (suction), which then pulls the valve open, against the return spring. Think exhaust valve...

Just had a mad thought- this might be the source of your extra air leak- the air might be getting sucked in through that open hose???

Edited by mk2
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On 5/19/2019 at 9:47 AM, mk2 said:

Just had a mad thought- this might be the source of your extra air leak- the air might be getting sucked in through that open hose???

 Yes that's what I thought initially because of the part that's missing (had a look for one but can't seem to find one anywhere), but saying that after taking off the EGR valve (think it was stuck closed) giving it a good clean and scraping out and getting the valve to open again, then doing a re-set on the fault light, touch wood the engine light has stayed off for the past 5 days, so fingers crossed its sorted, 

 

 cheers for your help folks

 

  LL  🙏

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