7 replies to this topic

[Nomorelogic]

so my car had a idle problem, stalling at stops and so on, fixed that with a new idle air control valve, so happy about that, then the car ran perfect for like a month maybe, but then got a new problem, which is massive amounts of over revving now, doing about 3-4000 revs as soon as i put the clutch down, it also has a cruise control type problem which is really annoying, i have to have my foot constantly on the brake when crawling because the engine will go upto 4000 revs when the clutch is down, turning heads, causing noise, drinking petrol and overheating the engine,

i have checked for vaccum leaks and there are none, what else could it be please help me
what can i look for ?
also
i have a fault code cable but no software to check for anything else ?
does anyone have any idea of programs that will work for ford fiesta mk4 1996, any i have looked at are for vw, or brand specific ones for their own devices.

any advice would be great because the car is driving me crazy
liam

[fredflintstone]

Hi Liam

just try these three things:-

1.Has your car got a clutch pedal switch...if so this could cause fault.
2.If you have had a new IAC Valve disconnect and try starting car this will make ecu pick up fault...reconnect IAC and start, ecu should clear fault
3.Disconnect battery for a period of time 40minutes ish

Let us know how you go

[Nomorelogic]

hi fredflintstone i have tried removing the sensors for the idle air control valve, when removed the engine will barely stay on, then stall after 5 or so seconds, when i put it back on no change though, its only when the car gets warmed up does it start the overrev thing, it will be fine until you go over 30 mph then its like that until you turn the engine off, i also tried the battery to no avail, it doesn't seem to make a difference, i heard shorting the positive and negative leads would shock the car and reset completely everything, but i heard doing that would set off the air bag ! is this true ? i have a diagnostic testing lead to go into the obd-ii socket but cant find a program that will work with my car 1996 mk4.

i have yet to try the clutch position switch, i took it off and it made no difference, the switch must have been faulty altogether, unless you never notice a difference anyway, if it is that how would i find it ? just go to the scrap and get a bunch of them, chances are they are either not working or are off a different model , or does it matter, i know the maf from a different model with numbers made a difference and not in a good way.

sorry for the late reply i was sorting out another problem with my car, the back right brake cylinder failed and scared the s*** out of me, then after repairing it, the new replacement went too !!! IDK what's happening there, they were fitted correctly, maybe just a dodgy part i got it from rolllings but obviously not that good, or could it be the servo

thanks very much !!!!

[fredflintstone]

Hi Liam

Firstly DO NOT start shorting the battery...apart from being dangerous you could do more damage to the vehicle...Air bags deploying...No cannot see that happening, air bag systems are very clever/complex and a short circuit should not do anything like that.

When you disconnected the wire from the IAC valve did the engine management light illuminate???

You said it does it when it gets warm...errmmmm tricky one becuase if no MIL (Malfunction Indicator Light) is coming on then you can buy software but I would put money on No TC's(Trouble Codes) will be logged.

Going back to you saying when its warm...then I would start looking more down the line of temp control to ecu, ie Coolant Temp Sensor....If the coolant temp sensor is faulty then as the car warms up the resistance in the coolant temp sensor changes telling the ecu to change fuelling, as you can imagine if those resistances go too high/low the car will think the engine is cold so it will feed it more fuel..thus revs increase

If clutch switch was at fault it would do it from cold not just warm.

Another reason why I say temp sensors is if the ECU is being told the engine is cold then no MIL will illuminate as it doesnt see a fault it just thinks the engine is the temperature its being told.

To do a simple check on CTS you need a multimeter? If you have one let us know and I will talk you through the testing and what to look for. It is a simple test and illiminate/diagnose it instantly.

[Nomorelogic]

Well i replaced the clutch sensor , no difference and any sensor i unplug shows no light on the dashboard, broken light ? maybe, but nothing, the car will stall now if i unplug the IAC, if it doesn't, the engine spins really slow, and vibrates and shudders, like its spinning uneven, if that makes any sense sounds like its grinding, when first starting the car, it revs at about 1800rpm maybe, and roars, then after about 10-15 seconds, it slows down , almost like the revs are too high, but if you turn the revs down slightly, the car will rev too slow and stall (or at least it would, before the whole crazy idle thing started, which i cant remember how it did start tbf, i dont know if i had mentioned this before but the high revs pull the car like it has cruis control for about 10 seconds then it realises that im not actually accelerating then slows down.

i didnt actually mean the battery itself, i meant take both positive and negative leads off then touch both leads together not connected to the battery, i do have a multimeter but have no idea where to find the sensors really, if you can describe where they are and what to test i could do it simply, some people say to check that the TPS has a voltage of either 0.4 or 1.4 i cant remember but how would i test for that also, or could my ecu be faulty, there is like a 1000 things it could be and the garages are only interested in trial and error we shall replace everything kind of thing and ford wont look at me twice, its a 16 year old car

thanks for your help

[fredflintstone]

Hi Liam
I m surprised disconnecting the IAC doesnt put the MIL light on, it should..yes you could be right about ecu but no easy way to check without proper tools and wiring diagrams tbh.

As for the TPS yes this could also be at fault, I believe you can reset them on fords but dont hold me to it...Turn the ignition lights on and press the throttle down to the board slowly and slowly back up...do this about 5-6 times and start the car see if that makes a difference...But like I say ford isnt my speciality so it my not work

Have you also checked ALL hoses from/to TPS and IAC..it could be a simple as one of those split.

Try the reset on the TPS and let us know if it works or not.

You are bang on with garages...what we call in the trade "replace to repair"...but thats the difference between a fitter repairing the car or a technician diagnosing it correctly..

And disconnecting the battery and rubbing the leads together is something I have never come across in 25 years in the trade..and it certainly wont set your airbags off.

[Nomorelogic]

hi again,

the cars brake cylinder blown the other day 2 in 1 week, dont know what happening there, so to be safe bought complete new back brake including cylinders, pipes drums and shoes, so its still being repaired, i can get to it until tomorrow afternoon, so ill check the tps reset thing then, you said there was a solution or something to check on the other posts have you got that information for me ?

would rubbing the battery wires together even do anything ? either beneficial or not, i will try to reset the ecu, but what do i do then ? how long to wait, and how do i know its even done anything ? do you have the name of some diagnostic software that would work on my car, if i have a name i know what to look for then , you say you work in the trade so you might know this stuff better than me.
also changed the clutch position sensor made no difference, no cracks that i can see and another vacuum test with wd40 spray showed that there were no leaks anywhere that i tested, and i thoroughly blasted anything i could see

thanks for all your help so far

[Nomorelogic]

once i have the car back after the brake fitting i will try to take a video and post it here, see what you think