Starting problem with Fiat Brava

[Graham Carr]

Hi,

I was wondering if anyone would be able to assist me with the best way of solving a problem which has appeared on my Fiat Brava (1.4S, N Reg, 1996).

The problem is as follows:

The car starts okay when the engine is cold and it also starts okay if the engine is fully warmed up and you switch it off and straight back on, however if you leave the car for a short period (e.g. the time it takes to do some shopping, etc) and try to start it, the engine turns over but never starts. It can take up to 5 minutes of attempting to start it before it does start up correctly.


I have taken the car to two FIAT specialists, they have checked the ECU for faults but none are displayed, and therefore they have told me that they do not know what the problem could be. I have changed the HT leads, spark plugs and all filters but the problem still exists and obviously this is not an acceptable solution for me.


If anyone has experienced a similar problem and found what the solution was and/or knows what may be the cause, I would love to know.

Cheers,

Graham

 

[Anonymous]

I am very surprised that neither of the Fiat specialists changed the Lambda Sensor, its usually the first thing they say and in this case it could be.

The sensor is screwed into the exhaust manifold and if it has a problem the heat could be adding to it. However, usually issues with this tend to show up on the diags.

The sensor is fairly straight forward to replace

N

 

[Graham Carr]

Hi,

Its funny you should mention the sensor being on the exhaust system, as I had a new exhaust fitted onto the vehicle just before the problem started to appear.
What does the sensor actually do and do you think the replacement of the exhaust may be an issue?

Cheers,

Graham

 

[alfanige]

Explenation

The so called lambda sensor is an exhaust gas oxygen sensor which is utilised in motor vehicles with three-way catalysts for the reduction of pollutants in the exhaust gas. It monitors the concentration of oxygen in the exhaust gas in order to keep the air-fuel ratio within tight limits, close to the optimum catalyst efficiency which is at the stochiometric ratio for complete combustion of about 14.7 kg air per 1 kg petrol.

Allegedly!

And yes they may hvae knocked it or biggered it up in some way!

Nige

 

[judge judy]

thats not my old car is it?

you didnt buy it in nuneaton did you?

anyway had this exact same problem. it wasnt caused by the temp sensor on the thermostat housing (replaced), which tells the engine stuff on correct fuel mix to engine temp etc. my grease monkey had it connected to his gas sensor and all emissions were spot on, so he thought it unlikely to be lamda sensor

the local garage who had it said that the crank angle sensor was being reported as busted, and this was causing the problem.

unfortunatly before could get this fixed the tensioner broke up, and dumped all the valves into the engine. the garage then bought it off me for £300, he could have had for f all, but i played it cool.

anyway hope this helps

cheers

i'm firm but fair

judge judy

 

[Graham Carr]

Hi,

Thanks for all the help you have supplied so far, it could well be this that is causing the problem.

I thought I should ask however that in the last week I have noticed that the exhaust is blowing from where the new exhaust was joined to the downpipe from the engine itself (not sure how long it has been like this), so I am taking this to be looked at this weekend as the exhaust is still under warranty.
My question is, where abouts is the sensor located and could a hole in the exhaust be letting in air and thus giving an incorrect reading to the sensor or have even damaged it?
I also thought I should mention that sometimes the car gives off a very strong petrol smell, usually when it is very warm (i.e. sat in traffic, idling, etc), could this also be due to an incorrect lambda sensor reading/sensor?

Cheers,

Graham

 

[Graham Carr]

Hi,

The first FIAT specialist I had the car into did the following:

1) Checked ECU and said it was reporting that the knock sensor was faulty - Replaced - Problem still apparent
2) Checked ECU again and said crank sensor was faulty - Replaced - Problem still apparent
3) Said problem was fuel problem - added some cleaning solution - problem still apparent
4) Decided that the ECU was faulty - got second opinion that this was not the case as could read from ECU fine

I then took the car to the FIAT specialist who gave the second opinion and they checked the ECU and all was okay, and said that was all they could do.

Since then I have replaced the HT leads, spark plugs and filters, but the problem is still there!!!

Ho Hum

 

[Nigel]

Blowing in the wind

Get the exhaust sorted out first, it sounds like this could be having an effect. If it still happens go back to the Fiat specialist and ask them to check the sensor out.

Le me know how you get on

N(ige)

 

[Anonymous]

Re: Re: Starting problem with Fiat Brava

I'm not sure this could be caused by a faulty lambda, the ECU waits a certain time after starting to allow the lambda to warm up enough to work correctly.

Sounds like it could be the engine temp sensor or a manifold sensor giving the ECU the wrong values making the ECU think its trying to start a cold car.

Next time it fails to start, crank it for a while and then take a plug out, if its covered in fuel then its going to be a faulty temp sensor and the ECU is flooding the engine.

 

[kev]

kev

Just for interest - is the lambada (whatever) sensor the 1 on ur downpipe - mines been smacked on a speed bump and theres a dirty gr8 big dent in the pipe - has ne1 got a spare for a 1.2 2001?? Also just to say that you should never start an engine for a few secs only - my dads astra got through three sets of valves that way - they just clog up and dont return - it is a p reg ecotech astra though!!

Regards - Kev

 

[Deckchair]

trouble starting when warm

The lambda sensor is ignored when starting and for the first few minutes as it will not be hot enough to record properly so it isn't likely to be that. More likely is the engine temp sensor as that will give the ECU a better idea of what fuel/air mixture to use but that wouldn't stop the car from starting for 5 minutes! A possibility is a head gasket leak. Are you losing water? What can happen is a small amount of water leaks into the cyclinders when it is just warm but doesn't happen when the engine is hot as it is evaporated immediately.When it DOES start after causing problems does it start on just one or two cylinders? Is there white smoke out of the exhaust? Have you had any problems or repairs done recently?

You say it starts OK from cold or hot but does it start strongly without problems or is there still a misfire?

Is your fuel injector electric pump running when you turn on the ignition (listen for it)

There's so many things that could cause your symptoms that the more info you give us the better.

 

[Graham Carr]

Hi,

Thanks for your response, I will answer your questions in order below:

1) The car is not losing water or oil, in fact I very rarely have to fill them up at all

2) I have not noticed any smoke coming out of the exhaust when it does eventually start.

3) Repair wise, in the time since I got the car second hand, I have had a faulty oil sensor replaced, a faulty Thermostat replaced and a brand new exhaust fitted. The problem appeared shortly after the new exhaust was fitted (as previously mentioned I have noticed it blowing from the join to the downpipe and will be getting that sorted this weekend), and the thermostat was replaced a couple of weeks previous to the exhaust!!

4) On the turn when it does eventually start, the revs are fairly laboured for a couple of secs and then pick up to normal.

5) If I turn on the ignition I hear a glugging noise for a second or so which I presume must be the fuel injector pump starting up.

As for other information, the only things I can tell you are as follows:

1) The car appears to run perfectly fine once started with no loss of power noticeable, etc

2) Sometimes when standing in traffic for a long period, etc, a strong smell of petrol is witnessed, not certain what could be causing this.

3) The car last had its MOT in May, and all emissions, etc were noted as being within the limits, thermostat and exhaust were replaced a couple of months after the MOT however.

4) I have had brand new filters (air, oil, fuel), HT leads and spark plugs fitted.

I hope this provides you with some more information.

Cheers,

Graham

 

[Anonymous]

Re: Re: Starting problem with Fiat Brava

Still sounds to me like the temp sensor or one of the manifold sensors.

Whats the MPG like?

Next time it gets into the not-starting state, take a spark plug out and see if its wet or dry. I think its flooding.

Also, have you tried cranking the engine over with you foot flat on the accelerator pedal when it won't start?

 

[Anonymous]

Re: Re: Re: Starting problem with Fiat Brava

2) I have not noticed any smoke coming out of the exhaust when it does eventually start. >

That's good



OK now did the thermostat need changing because the engine was overheating or over cooling? Over heating could point to possible head gasket gone, Over cooling not a problem

As regards the exhaust, the car should start well even if it had no exhaust. But I wonder if they've punctured a fuel line and you're losing fuel pressure on the return line. That would account for the fuel smell and poor restarting




Sounds like too much fuel on a warm start as you have replaced HT leads and plugs and coil is obviously OK as it runs fine otherwise so that points to possible eng temp sensor



Ok that's good

As for other information, the only things I can tell you are as follows:


OK


That's very worrying. Always check out any strong smells of fuel. There's the clue as to the overfuelling.

Need to get under the bonnet and under the car when it's just warm and check for fuel leaks. Turn the engine off and listen and look for fuel leaks. Check underneath, it could be dangerous with fuel spilling around a hot exhaust and cat convertor.

As Nige says take it back to the exhaust place and get it sorted pronto. Tell em you've got a strong smell of petrol and the car won't restart since they fitted the exhaust and they ought to come running with a fire truck!

 

[Graham Carr]

Hi,

Just to let you know the situation so far, I took the car to get its exhaust fixed which has now been done, but that did not solve the problem.

So I managed to find the number of a mobile engine tuning and fault diagnosis guy, who came out on Saturday to look into it.

Anyway after a good 3 hours testing this, that and the other, he eventually found that the cause is a faulty throttle potentiometer (it was givin strange, fluctuating voltage readings), but as you well know this is part of the throttle assembly and cant be replaced separately, so instead of forking out for a brand new one (extremely expensive!) i have opted for a second hand unit which when fitted should solve the problem.

At least I now know from the extensive tests that every other parts of the engine and electrics are fine

Thanks for all your help,

Graham

 

[Graham]

Hi,

Just thought I would let you know that I have now had a second hand throttle assembly put on my car, and can confirm that the starting problem is now nowhere to be seen

Cheers,

Graham