I’ve got a 1.2 Fiat Grande Punto and pretty much every time I turn it on it shakes and judders and will only start if I pump the accelerator.

The engine light is also on when I start the car.

( I think I can smell fuel but I might’ve spilt some )

Any ideas or help would be appreciated!

This vehicle is a SORN as I haven't been able to drive it for a while and has just been sitting on my drive. I'm trying to get it back up and running and I've recently replaced the battery after the last one died.

I can't tell you what the fault is but I can tell you exactly what the engine light means.

'A fault has been recorded'.


You'll need a code reader of some description to obtain the fault code from the ECU.


Your problem could be a multitude of things, everyone could offer advice as to what it could be, but unless you have the fault code, we could all be wrong, so don't chuck any money at it until you know the code.


How long has it been sorn and did it run OK when you parked it up.
It could just be damp if it's been stood for months on end.

However, Beg, steal or borrow a code reader and see if you can get the error code.

Thanks, i'm going to borrow a reader off someone so i'll know the code soon.

keat63 said:

How long has it been sorn and did it run OK when you parked it up.

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It's been a SORN for just under a year.

And when I parked it up it had some minor problems. Like it had engine clicking in low gear and problems cold starting ( The cold start problem was the battery it seemed ).

I'll get the code and then maybe I understand whats wrong more.

Just borrowed a cheap code reader off one of my dads friend and the codes which came up are:

02 sensor heater circuit bank 1 sensor 1
engine coolant temperature sensor 1 circuit

It doesn't register to me that a sensor could be causing shaky and sometimes failing starts, but I'm clueless, could this be the issue?

Also, I don't know how to fix these faults from the code reader, and can't find any video online or the components I need, could someone send me a video on how to replace them and/or a component listing?

Once again, any help is greatly appreciated.

02 sensor is the lambda sensor afaik.

mdlcarparts 2012..a very very informed and helpful shop/man on ebay. He goes out of his way to help and his parts are cheap AND gaurenteed.

Hey Tom, seems like you need a bit of theory...

Both sensors are invoved in the air/fuel ratio computation by the ECU, so YES they can and WILL dramatically impede on the way the engine starts and behaves.

The first error states that the heating element of the O2 (lambda) sensor has problem: this sensor measures the O2 contained in exhaust gases, then the ECU compares it to what it should be with the correct A/F ratio (14/1 ish) and adjust the injection accordingly.

Second error is about the coolant temperature sensor: the ECU needs to know the engine's temperature so it can adjust the A/F ratio accordingly. When a (petrol) engine is cold, the fuel vapor might condense on the cold inner walls, the vaporization is poorer so the final mix is too lean to ignite (properly). To compensate, the ECU increases the fuel amount being injected (that was the 'choke' on carb cars). If because of defective sensor the ECU think the engine is warm while it is not, the A/F ratio will be too lean and the engine will have a lot of difficulties to start and will be shaky until warm...

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)

here's where the Lambda's are located on a 1.4, should be similar on the 1.2. Also attached the coolant sensor location.

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)

Thanks for the answers and the theory.

I've currently replaced one of the components and re-did the code reader thing, but that specific code is still there. There is an option to "erase codes" but im not sure if that means like 'reset codes and try again' or 'reset codes forever!'

Should I reset the codes?

Hi Tom, which one have you replaced (I bet the coolant sensor) ?
Regarding the code, some of them, usually the minor ones, might clear the MIL ("engine" light) once the problem has been fixed and after a few "probing" by the ECU shown that everything's back OK. Some other codes won't clear the MIL and you'll have to remove them from the memory, so YES you have to erase/clean/clear the errors and check again!!

BTW: the O2 sensor heat element can be tested with a multimeter (ohms) on pins 2&3 sensor side as well as the feeding from the ECU (12VDC) pins 2&4 loom side @ connector level ...

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)

Bernievarian said:

Hi Tom, which one have you replaced (I bet the coolant sensor) ?

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Yes, you're absolutely right, I replaced the engine coolant temperature sensor 1 circuit one.

I'll clear the codes today and also replace the other part, thanks.

The man/shop I referenced earlier sells 02 lambda sensors ,delivered and guaranteed for ....£10...I have one on my shelf that I didnt use...

Sorry for the late reply. My life is falling apart, as well as my fiat punto.

I'm having problems checking the resistance on the O2 sensor. I did replace this but I hope I didn't replace it with a bad part.

I saw this guys post :
https://www.fiatforum.com/grande-punto/433189-p0115-engine-coolant-temp-sensor.html

And he said he had the same issues as me (his juddering problems don't seem as bad - but it's been quite cold where I am). He said replacing the MAP sensor could fix my car, it that worth a try?

Hi Tom, sorry to read you've had bad times...

Regarding the car, the (cheap)reader might have led you in a wrong direction since not all codes are documented. The manufacturer has a lot of "customized" codes that he doesn't have to share with others, so not all readers can interpret them correctly.

Multi Ecu Scan IS the reference ! Beside the fault codes you can activate devices (actuators, valves, lights, etc.) and you can also read sensor values and even plot graphs of them ! Doing so you would be able to tell if a specific one needs replacement.

As you asked the MAP, being a link in the A/F ratio calculation chain is a good candidate.

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)

Where are you based Tom?

MES is available in most of UK


southwest is main exception

COLD reference tells me you are not there..

Thank you Bernie

Bernievarian said:

As you asked the MAP, being a link in the A/F ratio calculation chain is a good candidate.

Click to expand...

So I should just replace the MAP sensor and see if it does the trick?

They're quite cheap, and I don't care too much if it doesn't work.

varesecrazy said:

Where are you based Tom?

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I am indeed from the south-west, it has been quite cold as of recent - not to say it's always cold.

How far into the S.W. ?

Access to MES might be possible

Charlie

Always better to get you the right tool FIRST. What I used to do when I needed one was borrow it from a relative (if available) but the next time I would buy it !! Now I tend to buy them even if I don't need them (at the moment), they will eventually become helpfull, or just pile-up somewhere in my (messy)garage ...
So even if a MAP sensor is cheap(ish) it's better worth (is that correct ??) to invest in MES...

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)

I will get a multi ECU scan and then come back with the results.

Good decision, but be aware that you'll have to also buy an adapter (yellow cable) to access all the nodes. Alternatively you might also buy the "multiplexed" version: a bit more expensive but WAY more practical !

BRs, Bernie

I decided to buy a MAP sensor and a Multiscan-ECU at the same time.

I tried to use the Multiscan ECU but I don't have a windows laptop ( I'm an Apple fan-boy, so I have a MacBook ? ) so in my head, I was like "f*** it, I'm just going to replace the MAP sensor and hopefully that works".

I replaced the MAP sensor just now, and to my amazement, it works great! The engine started the first time! no juddering, no failed starts, no error codes ( after I erased and checked them again ), and idles at a good amount of revs.

Thank you, guys ( Bernievarian especially ) for helping me get my pride and joy back onto the tarmac. I'm so happy my car didn't end up going to the junkyard in the sky ✝?