Technical Punto Mk2 possible ECU problem- help !

[Wull777]

I have a 2002 1.2 8V Punto which 'appears' to be running constantly in 'limp home' mode- ie. the ECU warning light is flashing and as soon as it goes above about 2000rpm the engine cuts completely- it comes back on right away when the revs go back down. The ECU was replaced about a year ago and has been running fine since- I also bought another one thinking this was the fault but the new one did exactly the same. I bought a code reader but it shows no faults recorded and I've un-plugged each of the sensors one at a time and the engine has exactly the same symptoms. I've also replaced the ignition coils with no difference- help !- any ideas ??

 

[Ziggy122]

phlonic wheel learn?
let the engine warm up till fan kicks in
rev upto 5k rpm let it settle on.its own
repeat rev.sequence total.of 3 times it should sort it hopefully

sounds like ecu needs to learn.engine

ziggy

 

[s and b]

phlonic wheel learn?
let the engine warm up till fan kicks in
rev upto 5k rpm let it settle on.its own
repeat rev.sequence total.of 3 times it should sort it hopefully

sounds like ecu needs to learn.engine

ziggy

he says it cuts out over 2000 revs so how would he do a phonic learn?
not that it needs one of course can you even do one on a 16v?

i would suggest seeing as you wont have access to a fuel pressure gauge that you consider either a faulty fuel pump or associated firttings causing fuel starvation

this is a bit of a stab in the3 dark of course as proper investigation could really need to be done by someone competent and trustworthy rather than your approach of swap things and pulling things off (ps ive done this too mind before now)

 

[Wull777]

Hi- thanks for the suggestions- as you guessed, the engine won't rev above ~2000rpm, so it's not possible to take to 5K.
Fuel starvation is a possiblity, although it's a bit strange that the power to the engine completely goes at exactly the same point each time- could it be that the ECU is cutting off the engine because it thinks there's a lack of fuel ? Also, having seen previous posts, would resetting the ECU be worthwhile ?

 

[Wull777]

Should have added to this - the car has been with a Fiat Dealer as well !!- they told me that the ECU wasn't showing any failures , so they would have to fit a new Fiat ECU - at a price of over £500 and then view any codes it stored. (they spend around 4 hours on it and found out nothing more than this).
However if the original ECU in the car turns out to be okay, they won't take back the new Fiat one... the idea of the service Engineer was that we should just scrap the car.... pretty bad for a Fiat agent I thought....

 

[fingers99]

2 faulty ECUs seems rather unlikely!

There are folk out there who will inspect (and fix, if required) ECUs for a hell of a lot less than £500. And you'd expect any stored codes to be as accessible with the ECU on the car as with it in bits on a workbench.

So, entering the Dark Zone, what might cause what is effectively a hard cut at 2k rpm?

Electrical interference is a possibility. Check for:

Carbon cables. It's not beyond the realm of possibility that someone has made up and fitted copper HT cables. This is a no-no on modern fuel injected engines.
Non resistor plugs. The plugs -- from most manufacturers -- should have a R somewhere in the code.
Faulty crank sensors can sometimes cause a hard cut. Generally this is because the earth sheilding has become inoperative.
Faulty cam sensor.

I'd not rule out the fuel pump -- you should be able to pick one up at a scrappy cheap.

 

[Wull777]

Thanks for that feedback. I'll check out the points you list - I'm especially concerned about the crank & cam sensors & the fuel pump since they are more 'unknown', to me however I would have hoped that the HT leads and plugs should have been fine since it's been running well up until this point, however I'll check them out.. Cheers..W.

 

[Wull777]

SORTED !! - took a few weeks and some persistance, however it turns out that the Crankshaft sensor was faulty. I decided to buy a new one and try replacing it (given that other people have reported temperature related problems with these) - as soon as the new sensor was fitted - problem solved.... engine revs as per normal again.
The only small problem is that the ECU fault light in the dash still flashes (I tried to clear this using the meter I purchased but it still flashes). This is no real problem, given that the car now revs normally..

 

[danielb]

Mine had temperature issues with the crank sensor and temperature. Replaced and its fine, but now it's running properly, do the phonic wheel learn and It'll stop flashing.
Dan

 

[Ziggy122]

need to find out if its flashing cause a mis-fire is been detected
or its flashing cause the phlonic wheel learn for some reason has been reset?

Ziggy