Hi. I'm posting this on behalf of a friend who's asked me for help with her car. It's a W-reg (2000?) 1.2 SX 16v, and it won't start from cold without a lot of help. It basically seems like it's refusing to acknowledge that the car is cold, and trying to run it as if it was already hot. It starts if you give it some throttle, but as soon as you lift off, it splutters and dies. Once you get it warm (by manually adjusting the idle speed), it's fine.

It started after the car overheated & boiled over in traffic a week or so ago. The coolant has been refilled & bled and a gas test has been done to check the head gasket is OK. I left it idling a while ago and it overheated again because the fan failed to come on. I was wondering if the same sensor that monitors the engine temperature also activates the fan?

Some things that I have noticed (and rectified), bearing in mind that I had never seen the car before it overheated:

1. the throttle cable adjuster lock nut was loose (even after the RAC adjusted the idle too high in order to get the car running). I've re-set the idle to about 850 rpm when hot.

2. the throttle cable was not fixed into it's clip a few inches below the air intake pipe. I've clipped it in place.

3. the throttle cable outer is broken where the metal bent pipe meets the plastic bits. I've glued this, and strapped the cable so it holds it sort-of in place.

4. I think the fan fuse was missing. On the upper block of fuses, the third fuse in the right hand column wasn't there. I've put a 10A fuse in (I know it should be 7.5A, but I don't have any). Trouble is, I can't get the engine warm enough to get the fan to kick in anyway - it doesn't seem to want to overheat any more!! For this reason, I don't know if I've fixed the fan or not!

I've checked that there's a spark when I'm cranking from cold, and the injector light goes out before I crank & doesn't come back on. The fuel pump seems a little noisy to me, but I don't know fiats, so it could be normal. I've run it with the air intake disconnected from the filter as well, to ensure the filter isn't blocked.

I've also reset the ECU (disconnected battery for 45 mins) and then let it idle for 5 minutes before switching off & on again. I'll find out in the morning if this has fixed everything.

Does anyone have any suggestions as to what is wrong?

Right, firstly it's a Brava, not a Bravo as I thought. And the ECU reset didn't solve the problem. Are the fan and the cold idle controlled by the same sensor? And if so, where is this sensor (photos would be nice, as I don't know the underbonnet very well). Ta.

fan problems are not uncommon. there are 2 methods used to control the fan on this model, and this depends on whether or not the car has climate control (A/C). both methods are based on the coolant temp sensor.

if the car does not have climate control the fan simply comes on when the signal from the colant temp sensor triggers the relay to power the fan. this should happen when the temp gauge is slightly above the half way mark. if this is not working you need to locate the relay (on front side of battery tray) and use a multimeter to check the wiring. this is also prone to bad connections due to rust and dirt, so clean up all the contacts and grease them.

if the car has climate control the fan has 2 speeds. both are independant of each other, the higher speed coming on at a higher temp. this setup uses the coolant temp sensor, and also used a 4 stage pressure switch. if only one of the 2 speeds in not working it is probably due to a problem with the pressure switch.

the cold idle management on the 1.2 models uses the coolant temperature sensor. if the car is cold started the butterfly valve assumes a position that is based on the coolant temp sensor's reading (and battery voltage oddly enough). this change in position will effectively do the same as an idle speed control valve on other cars. if the temp sensor was faulty the butterfly valve would not adjust its position and cold idle problems would occur. similarly if the actuator that adjusts the butterfly valve position was faulty cold idle problems would occur.

since the coolant temp sensor is involved in both issues i would think this is a good place to start looking for faults. however since you have also found damage on the throttle body it is possible that this is also an issue and could suggest the butterfly valve is not adjusting its position.

also possibly an issue, on the 1.2 models the throttle position sensor needs to have its range learnt by the ecu. disconnecting the throttle body or battery can make the ecu lose this range, and the only way for the ecu to relearn this is using a fiat examiner machine. this is a common cause of problems on the 1.2, however these problems are usually a high idle (2500rpm) so it doesnt seem likley that this is a problem on this particular car, however it is something to have in mind.

if i had to take a guess, i'd say the fan problem is due to rusty contacts on the relay, and the idle problem is due to a fault in the throttle body. i'm basing that on the probability of how common those faults are on this model.

Cheers, Jug. I'll check the fan relay out the next time I see the car. Where does the coolant temp sensor live? It may just be a loose connector, so I could check this as well. Incidentally, the car does have AC & ATC, but I don't know the condition of the AC system.

If I do find the coolant temp sensor, is there a way to fool it into thinking it's fully hot or fully cold (open circuit or short circuit perhaps?).

if you look at the attached image it shows where the coolant temp sensor is.

the table also shows what the resistance should be of the sensor at a range of temperatures.

now that i've read about it i realise that the temp gauge can work even if the coolant temp sensor is faulty because it has 2 thermistors inside, one for the gauge and one used by the ecu.

if you stick a 6kohm (6000ohms) resistor in the 2 pins used by the ecu, you will simulate a cold condition. it the car then does a start cold ok, you know the cold start problem is due to a faulty temp sensor. (seems likely now that i know the sensor is actually 2 seperate sensors in one)

the 2 pins to use are shown on the diagram, its the 2 that are next to each other in the connector.

hope this helps

That is absolutely superb. :worship: I'll let you know how it goes.

any news?



or is he still trying lol.

give the guy a chance

I probably won't see the car again until the weekend, and I've got to lay my hands on a 6K resistor before then!! The owner's also said she may take it to a garage (not a FIAT one though, so she may struggle & probably get fobbed off) but I'm hoping I'll get my grubby mitts on it first to save her the trouble, and earn myself a few brownie points in the process. I'll let you know when I've tried it.

Well, thanks to everyone for all your help, but my friend has part-exchanged her Brava for a Toyota Yaris, faults and all, so I didn't have the chance to try any of the fixes.

I reckon the sensor was reading hot all the time, so the dealer she bought it off disabled the fan so it wasn't always running. She bought it in the summer, so had no real problems starting it back then, it only came to light when the cold weather came along, and then it overheated in traffic (in the snow).

Just my theory, but I will never know. Thanks again for your help anyway.