Technical Engine revs at 2000 RPM on idle

[Mike1alike]

The engine revs repeatedly to 2000 RPM. But it's not like when it's a vacuum leak, the acceleration increases smoothly and lasts several seconds on a vacuum leak, but it's a jerky and repeated rev, it goes up to 2000, it doesn't stay for more than a second, then it goes down and repeats indefinitely if I don't stop the engine or put the car in motion. So, I think the problem is all the time, but at idle it is very obvious, through this repeated raising of the revs.
Here are some recorded parameters, in the attached photos.

I'd say it stands out the following:
Engine load: from 7.5kg/h on normal functioning, it increases up to 20kg/h. A little detail, on cold start engine works nice, the problem appears when engine gets hot.
Evaporation canister control: it became active although when I did this test I did not move the car, it was parked all day but the atmospheric temperature was very high. In fact, this is how this problem first appeared, after I refueled and the pump kept blocking, I wonder if gasoline did enter into carbon filter (is that possible?) when I refueled. So it had oscillating values, it moved between them, returning to 0 between the other values ​​and continuing this dance.
I suspected the coolant temperature sensor, but it indicates the actual temperature in the computer. It started at 75C (I had started the engine before) and then it kept rising, as I said, it seemed to me that it indicated the correct temperature, I don't think the problem is from here.
Idle actuator (Step motor): had high values, much higher than the normal ones for idling, I think it was also 90. But I do not think there is a problem here, I think the ECU gave this higher opening command due to that increased Engine load recorded.
Another detail: having the windows open during the test, it seemed to me that there was a smell of burnt / hot rubber.
My first suspect is the accessory pulley on the flywheel. Its disc consists of 2 metal parts attached to each other with rubber, inside (it is not visible). At a glance there are no traces of molten rubber on the body of the pulley. But as the car manifests, with this repeated and jerky increase in speed, this pulley is my first suspect.

Any other ideas?

 

[Mike1alike]

Looks like I have found what was causing the problem. It was not the pulley I've susspected, the pulley looks realy good, but it was in the accessories belt area, the adjustable tightener was at fault. The roller was being blocked by the deformed cover that was keeping it in place and so there was touching and friction where it shouldn't have been. That's where the extra engine load was coming from.
And by the looks of it I think it took it some time to get in that state. And I think the early effect of the blocked roller was the problem that I've had, the revv dropping down to 500RPM on idle.
For now I took that deformed cover off and placed a washer instead, the washer is pressing the inside of the bearing of the roller and the roller moves free now.
The engine runs free now and normal, good rev on idle. The problem seems to be fixed.

 

[Mike1alike]

Update: the revving problem is still active even though I have release that blocked roller.
So I remembered that before that problematic refueling, I poured 2l of gasoline into the tank, from a bottle. But I did not used a funnel nor did I pushed the little plastic cover at least for half of that bottle. So, by the looks of it in the first picture here, I'm guessing I've flodded the evap carbon filter. And that is why the pump at the gas station kept closing, there were lots of gasoline vapores that triggered it.
So now I parked the car into the sun with the tank cap off and I hope the gasoline in the carbon filter will evaporate. I've let it like in the second photo, with a plastic bag pushed to the tank line and the little holes of the carbon filter opened.
Please give me some advice if you think there is something else I could do to fix the rev issue.
From what I've checked there is no vacuum leak and that is confirmed by the diagnose I did, the manifold pressure was good, between the correct numbers.

 

[Mike1alike]

After more than 3 hours in the sun with the cap opened, no difference, the engins still revvs. I've tested the cranckshaft sensor and it works fine, it's not it causing the problem.
I've placed a tightener around the little hose of the breaher, the one that goes into manifold. It was oily around it and I thought there is the place where vacuum leak could occure, but no difference. At least I hope that the hose is tight now and no oil will get out.
Any ideas, anyone? What is causing this 2000+rev on idle?

 

[Mike1alike]

Do you guys know, is there any temp sensor, other than the one next to thermostat? And if connected to ECU, the temperature looks to be the real value, is it possibile to have another sensor that is faulty and is the cause of this revving problem?

 

[Mike1alike]

The problem is still here.
I saw a guy giving very bad advice, to obstruct the air intake. It does have an effect, but is not a fix so I strongly do not recommend that. I have tried it, but after that I've let the air channel opened.
You can see it here:
https://youtu.be/5wtLo5dB4bU
I've also discovered that the car was short on antifreeze, I topped it up with about 400-500 ml. I thought this is it, there were air pockets in the system and because of that the temperature is being read intermittent and that's causing the problem But is not like that, after topping up and bleeding, the engine runs the same. And it looks to me that the antifreeze got lost throughout the radiator cap. Although it is relatively new, the valve on that cap looks to be stuck open. I can blow through it with no problem. I've ordered a new cap, a better one.
And one other issue is the quality of the coolant. After I topped it up, I found something that shouldn't be there, on the cap, is in the photos. It was not oily at all, there are no signs of oil ìn the coolant, that felt like sawdust, only less harder. I will do a flushing and cleaning of the system, just can't figure out what that thing is.
And regarding the rev up problem, I have anothe thing that I suspect, I will try that tomorrow and will post the result, I hope to be a fix.

 

[TurboToppolino]

Just an idea, does the TPS ( throttle position sensor ) need recalibrating or replacing?
I only mention this as i’ve just replaced a TPS on a 2007 Ducati monster which is the same shape/ fittment as a punto.

 

[Chris parry]

Try Cleaning the crank sensor (If you haven't already).
I had a surge problem cleaned then changed the crank sensor (because I found isolation cable was a bit damaged and all good now

 

[Mike1alike]

Just an idea, does the TPS ( throttle position sensor ) need recalibrating or replacing?

No, the TPS works fine, it shows accurate position. On idle is 0 or .2 (which does not make any difference) and as I press the acceleration the value increases accordingly.
How did you managed to get the TPS out of the TB? And are TPSs on the market? I was under the impression that if there is a problem with the TPS the fix is to replace the TB which comes with the TPS and IACV on. I guess I was wrong.

 

[Mike1alike]

Try Cleaning the crank sensor (If you haven't already).
I had a surge problem cleaned then changed the crank sensor (because I found isolation cable was a bit damaged and all good now

I did clean it and tested it. Is showed variable voltage when I put a metal next to it, so it looks to be working. Done the test after I heated it up, showed kind of the same. If it would be faulty, I don't think it would show voltage, or would it? The resistance acted the same. Without any metal close to it, is about 1kohms, amd it changes while a metal is near. Actually, looking on those results it seems that while it was hot, the resistance dropped down a little bit more than while cold. Could this mean it is faulty? What surge problem did you have, how did the car act?

I've performed another diagnose testing and the same thing gets my attention: Engine load. When I started the engine (did not get to record it), it ran fine and the engine load was 7.125 kg/h. Then it started to rev up and the load was 20 something. If is a load in the engine, the ecu opens the IACV to give it more air and injects more fuel, according to the air intake quantity, so that the engine would run smooth. So I think this is what I need to find out: what causes that increased load? The AC was off, so it's not from there.
The other thing that I tried today was replacing the accesories belt with a new one. I thought the one I had may be slippery and that is the problem. But it made no difference.
I also replaced than that radiator cap with a new one. Strangely, for some minutes it ran nice, I thought that I've fixed it. But than it came back again.
I did not flushed the cooling system yet, but could whatever is in there to cause this problem? Could some problem in there be registred as an increased engine load?
Another thing that I'm taking into consideration now is the oil pump or maybe just the oil. Last time I did not give it a good quality oil (I don't now which one would be good quality), I've kept putting Selenia in the past, but because it kept needing topping up, last time I choose Mobile1. So, a problem with the oil, or the oil pump, causing some friction (not lubricating correctly) would go as an engine load, I'd say. And as soon as the engine accelerates, the lubrication is done correctly again, or somehow the engine load drops, but when idling normally engine load spikes up and so on...
Is there something, some sensors that mesures the force in the engine and according to that is the engine load calculated or is it just calculated by the air/fuel mixing and then the cranckshaft sensor is faulty?

 

[TurboToppolino]

If yours is the same shape as the one i changed, it’s held in by a round metal spring clip with teeth to hold in place. To remove try to squarely pull/ prise it out. The metal spring clip will be deformed so it’s single use only.
Ducati also say you have to buy the throttle bodies complete if it needs one……. Load of rubbish!

 

[TurboToppolino]

Another photo.

 

[Mike1alike]

This is what I found on the internet:
"load is measured by the MAF sensor. In other words, it measures how much air (and fuel) you're sucking into the engine and then compares that value to the theoretical maximum."
So, it could be a faulty MAP sensor (Puntos have MAPs that do the MAFs job), but I don't think it is faulty, or it is an vacuum leak that I couldn't find just yet. But considering that the engine does run even when I cover the IACV intake channel (the throttle body), I'd say it does look like an vacuum leak.

 

[Mike1alike]

I took the car out for a drive and this time it looks like the problem is fixed. I will pay attention to it, but for now all the signs are good, the engine runs as it should and very nice.
So the problem was the faulty radiator cap, with the valve stucked open. I didn't really bled it thoroughly after I've discover the faulty cap and after I topped up the coolant. So it did have air pockets, but even if I would have bled it, with that cap the problem would have reapeard. And clearly the pressure inside the system was low and it should be 1 bar. Higher than that, the valve should open.
And placing the new cap it managed to get the correct pressure and I'm guessing it even bled itself throughout the valve.

 

[Mike1alike]

The problem is back again.

 

[Chris parry]

Mike sorry to hear the problem is back again.
In reply to your question about my crank sensor. First let me tell you I cant get the fiat scan ect to work properly on my car so just do old fashioned fault finding not computer readouts.
My serge problems always started when the engine warmed up. I deduced eventually after checking many things that the plastic coating on the sensor wires had broken down and when the engine warmed up it warmed the wires up which was allowing them to make some sort of short out to each other! Point to note the outer sleeve looked ok but after I replaced the sensor I cut open the wire and inner wire sleeving was melted a bit

 

[Mike1alike]

I've teste with oth a new crank sensor. It does exactly the same. Tested with new MAP sensor, the same. I now purged the coolant. It looks bad, very brown-black dirty. I will replace it. For now I've put just water into the system. At first it ran ok, eventualy it keeps revving up. Some weird things came out of the cooling system as I topped it up and done the bleeding. Troughout the radiator cap came something looking like that thing that i've taken a photo of, on the cap, only hardened. There were some pieces of it caming out with air. The engine ran nice, than I've placed the car with the front end higher and the coolant level started dropping down. Untill I've put the hands on a new bottle of demineralised water, the revving started again. Then I topped it up and bled it, but no change.
The thing is that when I first start the engine, it runs ok for a couple of minutes. If I accelerate it begins to rev up, if I don't accelerate it takes it a little more time but it does rev up again.
It is really bugging.
Could the temperature sensor be faulty even it shows the accurate temperature both on the computer and on dash board? There is just 1 temperature sensor, right?
Could it be a step motor problem? It does appear to be open more than it's supposed to be, but I've thought that the computer gives it the command to open so much. I will check how that "engine load" raport is calculeted between the air/fuel ratio, but I'm thinking now that the step motor could have some problems. But on the other hand, another thing that is weird is that the engine does not shut down when I covered the throttle air intake. Maybe the evap was opening during that time and that is why it did not shut down though.

 

[Mike1alike]

I still have a little bit of petrol in the tank, the one that I've put before the problem first appeared. Soon I will be able to see if with that petrol gone the problem will be gone as well, or if I can just write that off and the problem will still be there.

 

[RalphM]

Is the connector on the throttle peal clean and tight.

 

[judderbar]

I had a weird problem after changing the antifreeze where the engine revved up like that in a very scary manner and then settled down and never did it again.

If you have air going near the sensor it could create same weird problem?