(T) Fiat Punto 2002 1.2 8v won't rev past 3000rpm

Hi all, I did the self-adaptation reset and phonic wheel relearn yesterday but no improvement. The engine light is also flashing now because I can't get the revs up to 5000rpm to complete the reset. The revs seem to have dropped further over the last week, it now cuts out about 2500 initially but once the engine has warmed up it cuts out around 2000-2200. Crank sensor on order and I'll update this thread when it arrives, hopefully mid-week. I checked the part number and it matched up with the one I linked to with the wire attached (46774532).

Have you removed the spark plugs for comparison?

Thats a very odd running condition isnt it

I haven't checked them since the RAC guy replaced them 2 weeks ago, should I? The problem definitely isn't making much sense to me, especially now there's no error codes being stored.

Enough petrol in tank?

Half a tank.

You COULD interpret the MIL only after throttle is applied as a misfire..
Detected by the Lambda sensor in the exhaust

And somewhere it is 'failsafeing' by limiting revs

Plugs are cheap to check

Line them up in the order they come out..

Look for differences in colour

Ideally post some pics on here

I'll check them in the week. I did originally have a misfire code but this hasn't come back since the plugs, HT leads and coil packs were replaced. To me it doesn't sound like it's misfiring, and it starts and idles smoothly.

There's a thread on this forum from a few years ago (here), the guy had the same problem and posted a video of what was happening (here).
It's doing exactly that, revs cut out, engine light flashes etc but I can't even get it to 4000rpm.

Is it like

https://youtu.be/dlaD7xzOidQ

?

Someone else had this problem some time ago and when I suggested crank position sensor my suggestion was shot down by another member but it did turn out to be the crank position sensor.

I cannot say your problem is crank sensor but it could be and it is cheap and easy to replace.

Yes, but it seems more precise/timed than that. Cuts out at exactly the same point, in that video the limit seemed to fluctuate. I notice in one of the comments someone said it's crank sensor in response to another comment asking how to fix the problem, not the uploader of the video though. Fingers crossed!

Edit: just read the description, it was the crankshaft sensor!!
Edit 2: I should add that when I was looking at the 'parameters' section in Multiecuscan, the engine speed reading was bouncing from 0rpm to ~800rpm and seemed to be out of sync with the revs but I don't know if that was a lag/latency problem between the ECU and the ELM interface. Each time the revs cut out, phonic wheel status changed to "faulty" and returned to "OK" when I left it to idle.

The engine ecu picks up the engine rpm from the crank sensor.

That's why I'm hoping replacing it will solve the problem. It seems to make sense anyway. Need to get to the bottom of it by next week so I can return the unopened replacement ECU before I lose £120!

*****FIXED*****

Hi all, just to update this thread, crankshaft position sensor arrived today and has solved the problem! Thank you @jackwhoo for suggesting the sensor and thanks to everyone else for your help. The mechanics I spoke to seemed to think the car wouldn't start if the crank sensor was faulty but this obviously wasn't the case!

Only problem now is I've not managed to get the engine light to stop flashing since the phonic wheel relearn. I did rev to 5000rpm 3 times but I think it might be because I didn't allow the engine to warm up until the fan kicked in?

Anyway, thanks again for the help. I'm sure I'll end up posting again soon because I've got a list of other things to sort out with the car, it's not had a service in over 10 years!

Andrew

Yes, for the relearn you have to warm up the engine first, then do the sequence of 3 times 5000 RPM, keep it at least 3 seconds on 5000 RPM then stop the engine and start it again within 10 seconds.
Nice that you fixed it and nice it was a cheap and easy fix.
The car do not start, as the mechanics told you, when the crank sensor is faulty only when it is completely out and sends no signal. That way by recevieng no signal ECU is told that there is no movement on the crankshaft therefore gives no gas. But many times crank sensor does not go out completely and it just gives wrong readings by wich ECU injects fuel and of course, it is not optimal as it is related to the wrong readings. A common problem with crank sensor when faulty is that it works ok when cold and dosen't work when it gets hot and causes engine to stop. And as long it gives readings that are in range, although they are less than should be with a correct working sensor, ECU does not register any error like in your case Andrew. @jackwhoo Congrats, you were spot on with the diagnosis.