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Old 13-07-2011   #1
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Misfire on idle??

Hi guys, need a little help here its a bit of a long post so bear with me.....
I got a punto mk2 1.2 8v a few weeks ago and ive noticed its missing on idle, however i cant narrow it down to any particular cylinder. Its not a really bad miss and the engine is not shaking that much. However when sitting at traffic i can feel it through the floor and seat if that makes sense, its not all the time its just every 5 seconds or so.
Whilst driving its perfect and cannot notice any problem.

So far I've changed;
Spark plugs
HT leads
Both coil packs
ECU

None of these have made a difference at all and I'm running out of ideas, the head gasket,water pump and cambelt was changed weeks before I got the car would the timing belt being slightly off cause a crappy idle??
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Old 13-07-2011   #2
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Re: Misfire on idle??

i have changed the exact things you have changed, plugs, leads, coils, ecu, manifold and cat and recently had a headgasket done.

And its still misfiring but mine does it while im driving sometimes too!

Does anyone have a bloody clue why?
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Old 13-07-2011   #3
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Re: Misfire on idle??

Try a search on here mate Mine was the fuel pump of all things. Total found it out by pure chance.
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Old 13-07-2011   #4
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Re: Misfire on idle??

loosing compression??

piston rings worn, valve seats worn and not sealing properly...cheap spark plugs also do it...incorrect timing

mine is missing at low revs aswel if you let go a 2k revs in first gear engine shakes and can feel it miss no engine lights...but i know what the problem is on mine well i think i do lol
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Old 13-07-2011   #5
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Re: Misfire on idle??

Thanks for the replies guys, the spark plugs were bosch (never had a problem with these before) I'm getting a compression check done friday although I dont think this is the cause as it doesn't happen whilst driving. Fuel pump sounds possible is there any way to test this?
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Old 13-07-2011   #6
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Re: Misfire on idle??

well if you get the lead and the free program you can test all of this kinda stuff all the cilnderd coil packs the spark the injectors and the fuel pump i just done it all on mine as i was messing about with it as i got it today 13 quid for the lead and free software so you cant complain for what it does
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Old 13-07-2011   #7
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Re: Misfire on idle??

Got a link to this lead please?? I've been told by a few people that all fiat 8v's idle like **** surely this isn't the case...
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Old 13-07-2011   #8
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Re: Misfire on idle??

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Old 13-07-2011   #9
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Re: Misfire on idle??

Thanks will get one of those leads and take a look at some live data.
Got it hooked up to a snap on scanner last week and it reported 2 faulty coil packs, so replaced them and ECU along with plugs and leads, fault still there but now no code......
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Old 13-07-2011   #10
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Re: Misfire on idle??

What i done was clear all the fault codes and then when the light came back on i had alook at thank god i did.. as before it had 6-7 faults! but cleared it and then it was just the one fault.. the 7 faults were knocked up due to miss fire and back fire.. on a massive scale due to poor spark plugs that had gone past there use by date! so clear all the codes and then see what it says when the lights back on (if its on eetc...)
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Old 13-07-2011   #11
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Re: Misfire on idle??

Compression Testing might be next on the cards

But why did you replace the ECU - if the fault still occours - means old ecu was fine

Ziggy
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Old 14-07-2011   #12
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Re: Misfire on idle??

ECU testing will check out an ECU for 30 and only offer an exchange if its faulty. OK this makes them judge and jury but I believe they are too big to play silly beggars.
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Old 14-07-2011   #13
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Re: Misfire on idle??

Quote Originally Posted by Ziggy122 View Post
Compression Testing might be next on the cards

But why did you replace the ECU - if the fault still occours - means old ecu was fine

Ziggy
I replaced ECU because after reading things on the net and the fault codes pointed to it, e.g both coil packs faulty. As I said driving is fine its just the idle its going to the garage tomorrow to have timing and compression checked. Still no EML light and no fault codes so I'm guessing its a mechanical fault.
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Old 14-07-2011   #14
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Re: Misfire on idle??

had mine compression tested today and showed no faults and no codes and no light came on, im baffled!
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Old 14-07-2011   #15
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Re: Misfire on idle??

i had same with mine i re placed everything but its was my injectors i used a cleaner called fortie on ebay it workd fine aftet but i change them two thats the cheap way insted of 250 ecu try it m8
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