Hi there,

I've been reading this forum a lot, ton of useful info here, thanks all for that! However, I couldn't find any help to my problem. I have a 2005 Punto, not sure which mk. Now to the problem:

The car keeps cutting me off, seemingly random, sometimes at junctions, sometimes while driving. When it happens, the battery and other lights are coming on, just like when you stall the engine and it stops. As I try to restart it, the CODE light comes on, and the car doesn't start. I have to wait about 10 minutes, with the key out from the ignition to be able to start it. After that it starts and drives fine until another random point, sometimes 20 minutes, sometimes a week later when it stops again. Also, the car behaves a bit funny, sometimes powerless and sluggish under 2000rpm, sometimes revs itself to 2000 and back in idle, which goes away if I stop the engine and restart it in a minute. These might be completely unrelated to the cutting out, just telling you, to give as much information as I can.

Someone suggested that the battery could be the problem, so I replaced it with an almost new one. Only thing is, the one that was in it had 440A, the new has 340A. Could that be the problem? Or probably something totally different, I am completely clueless about cars. I really have to solve this cheap as I can, please help me figure out what could be the reason for all this. Thank you!

I am guessing the fault is arising from the immobiliser system somehow because it seems to me that the chip in the key is intermittantly unable to connect to the signal that should be transmitted to the key chip from the entrance to the key hole.

I suppose this happens for both keys?

It might be a minor fault that is easy to trace by checking the wiring around the ignition key barrel

Thanks for he quick answer! Unfortunately I only have one key for it I will check the wiring around there, it does seem like something like that could be causing it, but then again why does it start working after a couple of minutes? I was thinking something in the electrical system, maybe causing a spike or loss of power so the immobiliser cuts out. Or some problem with the ECU could well be a reason for all of my problems...but I'm just throwing in ideas as someone, who is totally incompetent...

I could take it to a Fiat garage and they would surely be able to find and fix the problem, but I'm trying to find the cheapest possible way out of this

Check the earthstrap from the top of the gearbox to the battery negative terminal for security, cleanliness at the terminals and corrosion of the cable itself especially the last inch or so before the bottom terminal.
Check the wiring and plugs to the sensor(s) at the top and bottom of the timing belt cover at the left hand side of the motor.
Self revving can be causes by dirt in the throttle body. Removing the air filter housing and cleaning the tb can cure it. While the af housing is off check that the inlet manifold is secure and the vacuum hose to the brake booster servo is properly attached at both ends.

Woah woah woah....

Sudden cut out and take 10mins before itll let you restart is a classic case if failing crank sensor. ...
Once cool its fine...

Id looking at test it when it cuts out to see if it doea go open circuit....


Ziggy

This is a classic ECU fault symptom on UNO Fire engines.
Replace the ECU.

Ziggy122 said:

Woah woah woah....

Sudden cut out and take 10mins before itll let you restart is a classic case if failing crank sensor. ...
Once cool its fine...

Id looking at test it when it cuts out to see if it doea go open circuit....


Ziggy

Click to expand...

With a code light?

judderbar said:

With a code light?

Click to expand...

Maybe so
When the engine stalls, the power suddenly stops
The immboliser might not like that

If the Key code light is going out after an Off then to ignition stage, i wouldnt worry

Ziggy

Ziggy122 said:

Maybe so
When the engine stalls, the power suddenly stops
The immboliser might not like that

If the Key code light is going out after an Off then to ignition stage, i wouldnt worry

Ziggy

Click to expand...

Never say never but when you start a car the voltage falls very low to around 10 , so the design will be sufficiently robust to handle a voltage drop of just over 14 down to 12.25 when stalling.

Thanks for all the ideas guys, I had a trip to my mechanic today, had him check all the things you've mentioned, but only found an air leak. That was fixed, but the car is the same **** as it was. I guess it is time for me to take it to the fiat garage, hopefully they'll be able to sort it out. I'll keep you posted about the results...if they quote a few hundred quids, I'll just set the punto on fire and buy some other car. Never had a **** one like this, but never again...

before blowing up your car, did you atleast plug it to a computer to see what error it logged?

I gave it to the garage I used to take it for everything, they plugged it in and said there were only"immobiliser" and "key" error codes in the system. I also told them to check out everything you guys suggested but they didn't find anything apart from the air leak I mentioned before. Maybe this really is something only a fiat specialist can track down, or they just suck at what they do at my usual garage Anyways, it is at the local fiat dealership for diagnosis now, they'll ring me tomorrow with the results, and I'll keep you posted. Hopefully this post will help others with similar problems out thanks for the answers!

This may be a long shot but im gonna say it cause its a pennies cost typa fix

There is a thin wire on the throttle body that is an Earth for the ECU (which has the immboliser partially built in)

If the wire gets corroded or snaps off - which has been heard of before
it causes failure to starts (immbo faults), and can cause sudden power outs (putting the immbo back in)

Its literally the left hand side, ensure its not green filled puss, give the terminal ring a clean and the throttle body as well

this may be all thats needed - and a penny fix

Ziggy

I got it back from the Fiat garage, not good news though. They spent an hour diagnosing it (for £84) and didn't come to a certain conclusion about the problem. They suggested another 2 hours of diagnosis (for another £168) to be exactly sure what is causing the problem. I didn't want them to do it for that price so I got just a bit closer to the solution. This is the info on the paper they gave me:
"Car didn't cut out on test by itself. Disconnected throttle body, which should have stopped it but it hasn't. Examiner thinks vehicle is a 1.9 diesel and vehicle has a misfire. Suspect fault with ECU but further diagnosis required for wiring checks"

They also said if it was the ECU, then the bill with part and diag and labour would come around £800, which is just too much, but also said, that if it's a wiring problem it could end up around the same amount. That was when I told them not to do anything further. I am thinking of buying an ECU, coil and HT leads off ebay (around £100-150 for all of those) and try to find a garage who would fit them for me or try and fit them myself. If it is in fact a wiring problem, I can still sell those parts for almost the same price, but at least I tried. What do you guys think I should do?

of course they suggested 2 more hours of diagnostics

I got it fixed and came back to post the update, hopefully it will help out someone else. I ended up ordering a refurbished, recoded ECU from ebay, it was £80, and two ignition coils for £60, two HT leads for £10 and four spark plugs for another £10 (of course I bought the wrong type so these were not fitted). I've done a bit of research and it suggested that along with the ECU, I should get all those other parts replaced as well, so I did. The garage I usually go to fitted them in an hour and also removed and cleaned the throttle body. Labour was £60. Altogether I got it fixed for £220 compared to the Fiat garage, who quoted around £800. Their suggestion to do more diagnostics was also probably a ripoff attempt. Since the service all symptoms ceased to exist, drives perfect, no stalling, no revving. Sometimes the check engine comes on flashing a few, but there's no loss of power or any other sign then, that would suggest something serious, but I will have to figure out what is causing it later on. Altogether I am very happy with the result, saved a ton of money and got the car working fine.

Thanks for all the advice in this forum, it really has helped a lot!