Fiesta 1.3 CFi High Idle Revs
Discussion
My 1996 Fiesta with the 1300 CFi engine has no engine breaking on the over-run, especially when hot. With my foot right off the throttle, say approaching a roundabout at the end of a fast stretch of road, the car hardly slows at all. If I dip the clutch, I can see that the engine revs are sitting at about 2200/2500 rpm and this figure then gradually reduces to about 1000 rpm over a period of probably 5 seconds or maybe even more (by which time I am perched on top of of the middle of the roundabout!).
Can anyone advise me please? Is this the fault of the engine management unit itself, the water temp sensor (gauge appears to read Normal), the throttle position sensor, the throttle plate control motor, the intake air temp sensor or the manifold pressure sensor?
All thoughts and suggestions very gratefully received.
Can anyone advise me please? Is this the fault of the engine management unit itself, the water temp sensor (gauge appears to read Normal), the throttle position sensor, the throttle plate control motor, the intake air temp sensor or the manifold pressure sensor?
All thoughts and suggestions very gratefully received.
Thanks, Rob, that is helpful. I guess that I'm probably going to have to work my way through all the sensors, one by one. As for the diagnostic light, I do get an orange light that comes on with the ignition but it goes off all of its own accord after a few seconds, sometimes even before I key the starter motor. (Also, it shows an airbag symbol?). Cars were much easier to diagnose and repair in the old days, before the advent of the microchip! Thanks again, Paul.
The light you see is the SRS (airbag) fault indicator, and is nothing at all to do with EEC IV.
if the car runs well except for the idle hang up, i'd look towards the CFI unit first. maybe the throttle plate is sticking, or even the throttle position switch is faulty.
Does the throttle pedal move when you turn the ignition on and then off? there is a chance that the large DC motor on side of the CFI unit is sticking.
The CFI system fitted to that vehicle is also known to suffer with leaking 'O' rings around the injector and also engine collant temp sensor mis reading.
An air leak on the emissions side would lead to a high idle speed all the time.
edited to add
the temp gauge runs from a seperate sensor,so don't be fooled by it.
>> Edited by Nighthawk on Thursday 2nd September 22:27
if the car runs well except for the idle hang up, i'd look towards the CFI unit first. maybe the throttle plate is sticking, or even the throttle position switch is faulty.
Does the throttle pedal move when you turn the ignition on and then off? there is a chance that the large DC motor on side of the CFI unit is sticking.
The CFI system fitted to that vehicle is also known to suffer with leaking 'O' rings around the injector and also engine collant temp sensor mis reading.
An air leak on the emissions side would lead to a high idle speed all the time.
edited to add
the temp gauge runs from a seperate sensor,so don't be fooled by it.
>> Edited by Nighthawk on Thursday 2nd September 22:27
Many thanks, Nighthawk; there's plenty of food for thought/testing here. The car does indeed run well and there is no immediate evidence of the throttle plate sticking. As for the throttle position switch, I guess that it is just a variable resistor, in which case an ohmeter should show up any problems there? I have just checked to see if the throttle opens when I turn the ignition on - the engine is still warm and I saw the smallest of movements the first time I turned it on but no further movement subsequently. Should it move each time or not? I too was wondering about the motor sticking - is it possible to lube it in any way? As for the temp sensor, I discovered only this evening that there there are 2; one for the gauge and the other for engine management. It's dark and I haven't yet managed to locate the second one which I believe is on the back of the block, somewhere under the inlet manifold. I have got some resistance figures from Haynes and might try sticking a 4.7 Kohm resistor in to simulate the sensor at fully warmed up temperature. Do you think that would be a reasonable resistance figure? I don't believe it can be an air leak problem because, given a few seconds, the tick over speed always drops back to just under 1000 rpm, it just takes far too long getting there. This said, what would be the symptoms of leaking 'O' rings around the injector? In the light of your most helpful suggestions, Nighthawk, my money is currently on the engine coolant temp sensor. I'll let you know of my findings when I have had another go at it all. Thanks again for taking the trouble to provide such helpful advice.
I think the last time i tried sticking in a resistor it was about 10k, but that was for poor cold running, it's NOT a ford fix, although there were many TSB's released to cover poor running on CFI vehicles.
I'm also wondering if the car could be getting a naff reading for the VSS (vehicle speed sensor) as this helps to control the return to idle when the car is in motion.
do you know anyone with a code scanner?
that will speed up the diagnosis.
I'm also wondering if the car could be getting a naff reading for the VSS (vehicle speed sensor) as this helps to control the return to idle when the car is in motion.
do you know anyone with a code scanner?
that will speed up the diagnosis.
Thanks, once again, for your thoughts Nighthawk. I don't know anyone with a code scanner but I guess that a number of local garages will have one (for a fee). If so, how competent must the operator be to obtain a successful diagnosis, or is it just a case of plug it in and translate the codes? All I want is for someone to say, " Your problem is ....." and I can then get on and replace whatever is at fault. A quick look on the internet suggests that to buy a code scanner myself would cost more than the car itself is worth. Pity because, as an electronics engineer, I could get very interested in properly understanding the business of vehicle diagnosis and, later, maybe also tuning.
Hi John
The EEC IV system employed on the 1.3 CFi fiesta is quite simple realy, If you can get a code read from the module, it'll usually give a description of the area causing concern.
from there, it's a case of getting out the old multi meter and pin checking.
Only the more complex systems like the ford dealers FDS2000 and the newer WDS will give guided diagnostic routines and probing routes with simple yes/no fault determination.
many small IMT's have snap on code readers or similar and would happily plug into the 2 pin SCL connector and give you an idea of which system is at fault.
This might well cost a couple of quid, but i can tell you it's far quicker and easier than manualy testing the system sensor by sensor.
feel free to mail me, or if your north west I could try and sort some help for you.
The EEC IV system employed on the 1.3 CFi fiesta is quite simple realy, If you can get a code read from the module, it'll usually give a description of the area causing concern.
from there, it's a case of getting out the old multi meter and pin checking.
Only the more complex systems like the ford dealers FDS2000 and the newer WDS will give guided diagnostic routines and probing routes with simple yes/no fault determination.
many small IMT's have snap on code readers or similar and would happily plug into the 2 pin SCL connector and give you an idea of which system is at fault.
This might well cost a couple of quid, but i can tell you it's far quicker and easier than manualy testing the system sensor by sensor.
feel free to mail me, or if your north west I could try and sort some help for you.
Many thanks to you both, 911mot and John P, for your interesting suggestions. The breather pipe is definitely still on because I have removed the air filter several times recently. I'll try disconnecting the speed sensor and see what happens. I would indeed have gone down the Halfords EEC IV tester route had it not been for the fact that this must be a very late P Reg Fiesta, with a 16 pin connector inside the car rather than the 3 or 5 pin connector under the bonnet. According to my researches on the internet, the 16 pin connector means a much more complicated language to talk to the EEC IV unit, requiring kit from Crypton and the like costing hundreds of £ rather than tens. Nighthawk has been most helpful with his offers of help and, when I can find a local garage with the necessary kit to just read out the fault codes, he will guide me from there. Trouble is, the first outfit I approached wanted nearly 40 quid. The other trouble is that I have got to get the car back from my young son! Thanks again for your kind interest.
Gassing Station | Ford | Top of Page | What's New | My Stuff