Loss of power/not running

[VivaGT]

Hi,

I was after some advice about a problem with my Ibiza. Its a T reg Mk2 Cupra Sport GTI, 2ltr 8v. It used to lose power going round fast bends and then it would coast to a stop, then it would start and go again no problem. This was never diagnosed but at one point the battery went totally flat and we charged it, repaired the earth strap and put new batteries in the key. The car the ran and drove for about a mile but then stopped, it now starts but won't keep running and it seems to be getting fuel but no spark. Any ideas?

 

[edc]

Fuel but no spark to any plug suggests coilpack on bulkhead of the king lead.

 

[DPJ]

Does it start, then cut straight away?

 

[crossedmike]

If turns over but doesnt start coil pack either dead or dying
If starts then cuts out crank sensor

 

[Biker]

If starts then cuts out crank sensor

An imobiliser fault will give the same symtoms, ie starts up but cuts out straight away.

 

[VivaGT]

Thanks for the replies so far. Yeah it starts then cuts straight away.

 

[Cupra Kid]

If it starts and cuts straight away i would say your having immobiliser issues. If the coil pack was fully shot then i wouldn't expect it to start at all.

 

[Caffienated]

Sometimes a crank sensor will stop it starting altogether.

On mine the wire to the sensor had been damaged by road debris or similar and to begin with shorted in damp weather, then moved on to whenever vibration brought the wires together.

Crank sensor can be tested without removal or buying new parts obviously would make sense to wait til the car's throwing a fit to test it...

 

[Caffienated]

Immobiliser shows up in VAGcom come to think of it too... Gotta say I've never had an immobiliser problem, but from posts I've read about them this could well be one.

You anywhere near Middlesbrough or Sheffield ?

 

[VivaGT]

Thanks for the reply. Local garage tried new coil pack and new hall sensor in the distributor but still same symptoms.

Caffienated - unfortunatley nowhere near Boro' or Sheffield as slightly north of Aberdeen. You mention about testing the crank sensor - how would we go about this?

 

[Caffienated]

No worries... if you'd been closer I could have come for a head scratch and plugged a vagcom in.

This link http://www.seatcupra.net/forums/showthread.php?t=266057&page=3 takes you to a similar problem.

Post 4 on the second page refers back to the original post on crank pos sensor tests.

To be honest, I'd read through both threads. They're pretty long, but there's loads of useful ideas in there and discussion about what you're seeing.

The test spec for the crank sensor shows some sort of test lamp in use. Iirc, you're only looking for high and low, so any sort of test lamp would do. I used a mulitmeter on mine...

Basically, ye crank sensor provides engine speed feedback for the ECU which goes into its sums for how much fuel to squirt in. Naturally, if there's no signal, (there would be one at idle if everything was working) then the ECU decides you don't need fuel, so the ignition can spark as well as it likes, nothing's going bang... Bit like the infamous Pug205 Tachymetric relay. You should have fuel at the rail even with the crank sensor down, you just won't have squirts from teh injectors cos the solenoids won't be being signalled.

Speaking of relays, there's a grey relay (#172? unsure) that the Golf boys blame non-starting on just as freely as we say 'Coil Pack' on this forum. I changed mine to no avail...

Good luck!

 

[VivaGT]

Thanks for the help so far. Update - got a local auto electrician to have a look, gave us 2 fault codes - 00520 'Air mass flow meter' and 17978 'Engine control unit blocked'. The feeling is that the ECU needs repaired or replaced, can anyone confirm/correct this?

 

[VivaGT]

Hi again,

Was looking for clarification on these fault codes please, does the 17978 one mean that the ECU itself has a problem or is it something like the immobiliser is blocking the ECU from operating? Really looking for guidance on whether to send ECU off for repair or if it is an immobiliser fault. Also if anyone can shed any light on the 00520 code that would be good aswell. Thanks.

 

[VivaGT]

Sorry to be a pain but can anyone tell me how to disconnect the ECU? I have got it unbolted but the wires are still plugged in, not sure how to unplug them without damaging it? Did a search on the forum and found a thread from a couple of years back where someone mentions a sliding clip system but I still don't understand how this works. Would post up a picture but I don't think the forum will let me.

 

[crezz]

one end of the clip pushes one way to release the main harness, once thats done it should be pulled off.. have you sourced a new ecu?

 

[VivaGT]

Thanks for the info crezz, however we thought we'd try a few more things before unplugging the ECU. From the beginning the car has had new coil and a new hall sensor. The distributor turns and the engine turns over freely but no spark at the plugs. We did have the car scanned and got 2 codes; 00520 'Air mass flow meter' and 17978 'Engine control unit blocked'.

Having searched other threads on here we have tried leaving the ignition on for 30 mins to reset the immobiliser etc. and also unplugged the wiring block from the back of the ignition switch and hot-wired it but to no avail. Car turns over but still no spark. We're inclined to think that its the ECU and would send it off for repair but would like to be sure before unplugging it. Also wondering if it may be the ignition switch transponder, is this the black circular thing around the top of the switch where the key goes in and has a wire going to the immobiliser? Is there a way to test this or if it needs replacing, how do you remove it?

Really lost for ideas and would be grateful for any thoughts or a sequence of checks to make which might help identify the problem because its more than possible that although we have checked many things not doing them in the right order may be the problem. Thanks.

 

[VivaGT]

Hi again, ECU has now been repaired, but our other fault code was for the air flow meter.

We have a couple of further questions, firstly; could a faulty air flow meter spike the ECU if we just connect it up again - should we replace the air flow meter as well? Secondly, is there any process we need to follow when connecting up the repaired ECU (it has been made free-running)? What I had in mind here was that for our Fiat Punto you have to carry out a phonic learn cycle - ie. rev it up to the limiter 3 times so that the ECU learns the crank sensor position - is anything like this required on the Cupra?

 

[VivaGT]

Update; Finally got this solved, replaced ECU but still wouldn't start, now runs after replacing the crank sensor so it seems that the crank sensor was the problem. Just thought I would post this in case anyone else has a similar issue.

 

[Caffienated]

Glad you got sorted!

I had a minor nightmare over the crank sensor year before last, which is why i now believe nothing that fault codes tell me unless I've worked through the system and checked everything else that can be checked first.

My take is that while fault codes can be useful determining complex things, trying to use them as a substitute for diagnosis like so many mechanics seem to do now (main dealers *not* excepted) is likely to lead to many things being 'repaired' that were simply not giving the correct reading because something else upstream had cut the power to it... This is why car repair books used to give good thorough system descriptions each section so that you could think it through and consider why something might be unexpected apart from the obvious possibility.

 

[chipmunk82]

My 16v has been running fine the last 7-8 months since purchase, until yesterday when it started dropping the revs and the engine would stall, most times it would kick back into life but not always. It doesnt feel like its running full power either maybe 100-120bhp. The oil light started flashing when it cut out too but all levels are fine.
Haven't put it on vagcom yet but does this sound like anything familiar like coilpack as mentioned above?