Technical High revving all on its own

[fergus69]

Recently, my mark II Punto has been revving unnaturally highly after turning on the ignition. So much so that I have to turn off and restart (many times sometimes).

Sometimes it does this in the middle of a journey, and it is so high (it obviously affects the way the car drives too) that I have to stop in the middle of the road, engine off.

Help would be greatly appreciated. Thanks.

 

[Punto.Power]

Could be the stepper motor well its known to go and cause the car to rev to the limit, and only way you can stop it is by turning off the ignition.

 

[Xen]

is the stepper motor the ICV? i have a similar fault

 

[Punto.Power]

is the stepper motor the ICV? i have a similar fault

Yeah, Idle Stepper Motor (idle control valve ICV) it might just need a good clean with carb cleaner or it could be just nackard, but then again a faulty lambda can cause crap idle, you could even have a coolant blockage witch can cause the same symtoms as the first poster described by having to turn off the ignition, best bet is to get a diagnostic if you can. Mind you, a diagnostic can still fail to show the fault.

 

[Xen]

Yeah, Idle Stepper Motor (idle control valve ICV) it might just need a good clean with carb cleaner or it could be just nackard, but then again a faulty lambda can cause crap idle, you could even have a coolant blockage witch can cause the same symtoms as the first poster described by having to turn off the ignition, best bet is to get a diagnostic if you can. Mind you, a diagnostic can still fail to show the fault.

yeh, i had diagnostics done on it and it didnt show up, but i removed the tb and blew through the idle hole and it had no resistance at all - think its stuck wide open.

 

[TCelica]

I had the exact same problem, it's the car accelrator sensor, its broken and needs replacing. It will get worse and worse, if not replaced, such as when your sat waiting at traffic lights, it will begin to volunteer rev. Defenitly the car accelator sensor.

 

[The Sultan]

a faulty throttle position(tp) sensor can cause the car to open the idle control valve unusually but not normally aboth 3000rpm

a faulty idle control valve (icv) can cause revs in excess of 5000rpm

the big difference between the 2 faults is and (Icv) fault will not show on examiner as faulty (although there is a test feature on the examiner that will run the valve through various open positions and it's then up to the technition to judge weather it's working properly or not this is only how ether available to fiat technitions with fiat equipment

but a (tp) fault is obvious to diagnose as the throttle angle on the screen will be open when the throttle is obviously shut

both of these are replaceable items at a fiat dealer with special tools so don't go out a buy a hole tb it's a waste of money and may not fit your car due to subtle differences

hope this helps

 

[fergus69]

It sounds similar to what you said TCelica - it doesn't rev on max revs or anything but it is high enough to make me stop the engine in the middle of the road.

Can someone explain how the throttle sensor works then? I thought the throttle was controlled by a direct cable to the butterfly valve. If so, how would a faulty throttle sensor cause these problems?

How much money am I looking at to get a new one put in if that's the problem?

 

[The Sultan]

you have a cable throttle but there is a sensor measuring the angle you open it

it is likely the icv thou as a faulty throttle angle sensor cannot cause it to rev so high

 

[Xen]

Just wondering, whats the purpose of the TPS? surely since air flow is measured after the TB and the fueling is supplied to match, there is no need to have a TPS? so whats it do?

 

[spankysmagicpiano]

My classic Panda does this. Fine on the motorway on a long journey, come off and it goes mental. It's has gallons of carb cleaner through it but no joy. Not much help to you but just wanted to let you know you're not on your own

 

[Diss_50]

Same here as well had the same problem - ICV - Very embarrasing sitting at lights with Evos etc as if I wanted to race them with my granny in the car! whom I was taking to the shops lol . The mechanics I took it to just replaced the whole throttle body. Got a good deal on it as it was a 2nd hand unit from a young Mk1 Punto!

 

[Shaunyboyuk]

Id say clean your idle control valve first and see how it go's from there.

 

[The Sultan]

Just wondering, whats the purpose of the TPS? surely since air flow is measured after the TB and the fueling is supplied to match, there is no need to have a TPS? so whats it do?

no there is nor air flow meter on these engines

the injection system is (speed density)

it measures the manifold pressure (map) air temperature and the engine ecu has the engine speed and a fancy equation involving the size and shape characteristics of the manifold

the ecu knows from this how dense the air is and also how much the engine will be sucking in at set throttle angles and engine speeds

the throttle position sensor has a number of uses
1 pre warning to the ecu that the map is going to drop or rise
2 it tells the ecu when to take over the idle control automatically ie throttle completely closed

so basikly when you open the throttle the ecu takes a guess at how much fuel your going to need at that tp and engine speed it takes this guess from it's adaptive map

then it uses other sensors like map and lambda to fine tune the mixture

most of the other engine sensors are not quick enough to pick up on you quickly snapping the throttle open so it need the tp and adaptive map to allow it to be responsive

 

[Xen]

ahh i see, makes sense now cheers littlepip

 

[Xen]

Was most probably ICV in my case as a different TB sorted it

 

[Alan83]

I've the same problem as well and I sent it to the garage and I was told that the Throttle 'something' meter is spoilt and it's going to cost me 250 pounds on that. OMG... What should I do as I've just started going to this garage and I'm a foreigner. I'm not sure whether they are trying to 'chop' my money off. Some advise please... Thanks!

 

[fergus69]

Hi,

If you take off the air filter and have a look at the throttle assembly, you will see that there is a bronze coloured valve. My problem went away by manually pushing and pulling the valve, so I assume it was just getting stuck.

Alternatively, I was told that the problem could have been the Idle Control Valve (ICV). If this is the case then you can buy a whole new "throttle body" off somewhere like ebay. I did for about £15 just as a spare. My mechanic seemed to think that this would fix the problem.

The only other likely cause I can think of is the Electronic Control Unit (ECU) being faulty. However, leave this as a last resort as these can be pricey. The ECU is the black box just behind the throttle body.

Let me know how you get on, I'll help if I can.


Jon