neilcmusic said:

I tried leads and plugs , couldn't get one plug out but changed all others that seemed ok , I'm now thinking it's idling rough because exhaust has hole on , I have noticed something that may be related , underneath the centre of the engine there is a rubber hose hanging down , should it be attached to something or is it some sort of overflow?

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Hose hanging down from center of engine is extremely vague.
Find out what is on other end and someone may be able to help

conors891 said:

Hole in exhaust should just make it sound loud. It might effect the lambda sensor but that should just make the engine run rich rather than idle poorly.



My engine was running poorly before. Fixed it by changing the throttle body.

Before changing it I tried an ecu reset trick. It involves disconnecting the battery and shorting the leads for a few seconds. Then reconnect. Then turn on the ignition for 30 sec, then off for 30 sec, then on for 30 sec, then start car, wait for engine to heat up, when fan comes on for 2nd time turn off the engine. Then start again and drive. This is just from memory so perhaps someone here will correct me if I've missed something. Its worth a shot.

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If hole in exhaust allows air from atmosphere to reach O2 sensor the ECU will read air at O2 sensor as lean fuel/air ratio and add more fuel trying to correct fuel/air ratio. This will lead to excessively rich mixture which will cause problems through the whole rev/load range and eventually damage the O2 sensor and catalytic converter .

jackwhoo said:

If hole in exhaust allows air from atmosphere to reach O2 sensor the ECU will read air at O2 sensor as lean fuel/air ratio and add more fuel trying to correct fuel/air ratio. This will lead to excessively rich mixture which will cause problems through the whole rev/load range and eventually damage the O2 sensor and catalytic converter .

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Yeah you are correct, it may cause messy air/fuel ratios. I just know from personal​ experience I've disconnected my O2 sensor before and it still idles fine.

conors891 said:

Yeah you are correct, it may cause messy air/fuel ratios. I just know from personal​ experience I've disconnected my O2 sensor before and it still idles fine.

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Where is o2 sensor , I'm assuming that if I disconnect and all is good then it's a problem with the exhaust and I can fit new exhaust and reconnect?

neilcmusic said:

Where is o2 sensor , I'm assuming that if I disconnect and all is good then it's a problem with the exhaust and I can fit new exhaust and reconnect?

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In between the exhaust manifold and the cat. Some models have a second one after the cat too I think.

conors891 said:

Yeah you are correct, it may cause messy air/fuel ratios. I just know from personal​ experience I've disconnected my O2 sensor before and it still idles fine.

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Disconnecting O2 sensor will cause different effect on fuel/air ratio than an O2 constantly giving lean signal to ECU

OK , I'm going to have another go at getting the one plug out that was stuck , I'm just worried about damaging it , I removed lead from stuck plug whilst running and it effected running idle , now does this mean that plug is ok because surely if plug was damaged then removing lead from it whilst running wouldnt make any difference?

neilcmusic said:

OK , I'm going to have another go at getting the one plug out that was stuck , I'm just worried about damaging it , I removed lead from stuck plug whilst running and it effected running idle , now does this mean that plug is ok because surely if plug was damaged then removing lead from it whilst running wouldnt make any difference?

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well you now may have a fault code stored after disconnecting plug lead while running, can doing so damage ignition components if you don't ground the lead.


yes be very careful not to damage plug or head.


just fix the exhaust.

OK , I had my shredded wheat and managed to get the last plug out , it wasn't too bad but put a new one in anyway , still idles the same so short term I'll put new leads is and do exhaust which needs doing anyway and hope for the best , if the head gasket has gone I'm in serious trouble !

Shorting what out?
Never touch the battery terminals together ffs....

Leaving the battery off the car eventually shutdowna anyway safely....

As for the stuck plug probably needs more brute force....
I have in the past used a breaker bar to crack a spark plug loose

Oil in the well is all good an that
But sont go mad
Hot soark plug area and oil is kinda asking for disaster a wee bit - probably smoke alot too
A small amount and a hot engine may work tho

Ensure spark plug well is clean tho before


Also ensure the throttle body is clean too!

And exhaust holes do mess up
The person saying itll make a lambda say its lean / rich means itll compensate and it will sometimes cause it to run crappy

Ziggy

Holes and cracks in manifolds can cause bad running... happened to my first nissan, tiny crack in manifold... ran ok but hit a dip in the road or have a run up a hill from a dip in the road and it would start choking and stay at whatever rpm you was at.

Tried absoloutley everything and then after 6 months, the heatshield on manifold fell off one day when doing a service and there it was... perfect round crack around 3rd hole on manifold pipe bend... bought one from scrap yard and it never did that again.. it didnt even blow from the crack but under tension / flex it opened up and caused hell...

wouldnt crack in exhaust or manifold cause engine light to come on ? , im surprised that rough idling hasnt put light on , im getting a code reader tommorow , will code only show if there is a light on dash?

Not necessarily.
Get Multiecuscan and a lead to connect to your car.

Just spoke to previous owner , thr punto was sitting for 4 weeks and battery died , he jumped it , I've since read that ECU is lumpy for a while after this , if this is the case roughly how long will it take to learn driving style ?

Where is hole in exhaust system?
Have you repaired hole?

Does lumpy tick over after driving?

Have you checked air filter?
Changed oil and filter?

ECU "learns" quite quickly . It does not learn your driving style it tries to adapt to the engine from the sensor information it receives.
A phonic wheel relearn would be a very good idea.

jackwhoo said:

Where is hole in exhaust system?
Have you repaired hole?

Does lumpy tick over after driving?

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Still not replaced exhaust , have bought it but not done it yet , hole is rear of car in middle section am hoping to got this will solve rough idle however I've heard only causes rough idle if in front of cat ?

I would have thought the exhaust hole near rear of car is far enough away from O2 sensor number 1 to cause idle problems.

You really should get MES and scan for problems.

Ive jad 3 cracks on my punto manifold
1 on weld feom cat to down stream sensor

No eml

Crack around downstream sensor
No eml

And cant remember where other one was

But except noise i never lost power and car drove fine

If u dont have the gearbox mounted bracket - it can be why it cracks
Since i retrofitted a custom one back on after mine rotted - had no more cracks

Ziggy