Hi, I have a 2007 1.2 8v grande punto.

It starts perfect but then runs on three cylinders, I press the accelerator until it clears and then runs ok, it is also a little lumpy on idle when warm.

Does anyone know what this could be? I have a new coil pack, changed the spark plugs and leads. What else do you think I should check?

Flav said:

Hi, I have a 2007 1.2 8v grande punto.

It starts perfect but then runs on three cylinders, I press the accelerator until it clears and then runs ok, it is also a little lumpy on idle when warm.

Does anyone know what this could be? I have a new coil pack, changed the spark plugs and leads. What else do you think I should check?

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compression.

Thanks for your reply.

Do you think it might be the head gasket?

This might seem strange but it doesn't happen all the time, it has been raining today and when I finished work my punto started perfectly but then ran on three cylinders for a while but I also heard the alternator belt squeal. Could this be an indication of another fault?

I hope I am making sense

engine light on?

No eml light.

Was fine this morning, but it will happen again it comes and goes. Do you think the rain has something to do with it?

Just got back in from a drive and it is idling really lumpy. When I turned off the ignition I heard a grumbling noise, could this this be fuel starvation and the fuel pump need replacing. My punto has done 125000 miles?

New plugs, new coils, new leads and still misfiring ? How about ultrasonic cleaning injectors ?

Regards, Bernie

Flav said:

Thanks for your reply.

Do you think it might be the head gasket?

This might seem strange but it doesn't happen all the time, it has been raining today and when I finished work my punto started perfectly but then ran on three cylinders for a while but I also heard the alternator belt squeal. Could this be an indication of another fault?

I hope I am making sense

Click to expand...

If your alternator is squealing in the rain check that water isn't getting on it, do you have the modified scuttle drain fitted? https://www.fiatforum.com/grande-punto/337783-modified-scuttle-drain.html?337783=#post3360376

Also for your bad running have you checked the breather hoses? https://www.fiatforum.com/grande-punto-guides/262269-breather-hose-replacement-1-2-1-4-8v.html

Update...

I found out that the head gasket had gone so this has now been done as well as all breathers, coil pack, spark plugs etc. there is still a missfire on cylinder 2.

It starts fine but then runs on 3 cylinders, when I press the throttle over 3000 revs it seems to clear. Any ideas please?

Swap injector#2 with another one and see if the missfire moves accordingly, if not you can rule out the injector, if yes you get the culprit...

BRs, Bernie

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Bernievarian said:

Swap injector#2 with another one and see if the missfire moves accordingly, if not you can rule out the injector, if yes you get the culprit...

BRs, Bernie

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

Click to expand...

Thanks mate will try that.

I have swapped over the injector but still misfiring on cylinder 2.

Any other ideas? please help im missing driving.

What do we need to get a combustion ?

Fuel: you swapped the injectors with no result...
Air: a faulty valve could cause this, but would be permanent...
Spark: here we go ! Bad plug, bad lead, bad coil ...

Swap plugs from cylinder 2 with another and see if default moves.

Do you have the plug-on style coils ? Do swap them aswell and see for default move.

Finally, each coil receive its trigger from the ECU, verify connections (here you can' t swap !!)

BRs, Bernie

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

I have swapped over the injector but still misfiring on cylinder 2

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.

You mentioned that you've changed the head gasket? What was the original fault that made you change the head gasket?

A burnt or badly seating valve - it's usually the exhaust valve which bears the brunt of the combustion - can give misfire symptoms. A 'bent' valve - or a valve that is not opening and closing properly can also cause the same symptoms as a misfire.

You seem to have done a lot of fault finding work on your car - maybe now it's time to do a compression test. A compression test will tell you if anything is amiss.
Or maybe check your valve clearances first...

OP said the headgasket has been replaced, hopefully the mechanic DID check the head condition (valves) ... ??

@ OP:

- do you confirm this fault is random ?
- does it self-clear after a while (when driving)
- can you perform the plug swap ?
- can you perform the coil swap (if applicable) ?

A few bits about misfire detection:

- detection is disabled when cranking the engine: why it starts perfect...
- detection algorithm needs several misfire before throwing the fault
- once fault occur, the ECU switches off the corresponding injector: limpy engine
- this mainly is to protect the CAT converter from being destroyed by high temperature resulting of unburned fuel combustion...

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