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??

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?

Try a search on here mate Mine was the fuel pump of all things. Total found it out by pure chance.

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

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?

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

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...

http://cgi.ebay.co.uk/USB-DIAGNOSTI...k_rvr_id=244371112825&clk_rvr_id=244371112825

http://www.fiatecuscan.net/

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......:bang:

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...)

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

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.

Ziggy122 said:

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

Click to expand...

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.

had mine compression tested today and showed no faults and no codes and no light came on, im baffled!

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

OK, quick update. Today I had the timing checked, all spot on. Had compression checked, all good there also so this means it must be fuel related, I changed the injection rail earlier from a known working punto and yes the problem is still there. Me and my mechanic are baffled:bang:
Could a fuel pump cause a lumpy idle or is it a case of it either works or it doesn't.

Hello again Gavin

I'm not a gambling type but if I could I would bet you a quid that a replacement pump will fix your car

Mine is a year 2000 but the replacement pump was from a slightly later car with a different part number (will have a look in a sec if I can find my earlier post on this).

I have no idea why they miss at idle a bit yet drive ok under load. There's a few doing that from what I can gather.

My pump came from ebay, a good place to look for one methinks

Only thing I will add is, you will need to make/borrow/buy the tool to fit it as its really awkward without and your unlikely to manage otherwise.

A Tech on here may say if this is doable or not but I'd say its worth driving to a Fiat garage and doing the swap there having rented the tool from them if they'd let you? Where I work they have one that fits mine but it was sheer fluke.

I'll try and find the part number but it was say a 2003 pump

Good luck dude

Thanks shaun, I shall get onto looking at my p/n for my fuel pump when I get chance. Am I right in thinking its under the rear seats?? Also I've noticed its seems more lumpy when I'm on an incline

It is under the back seats mate. That when a tool will come in as the pump is held into the tank by a big plastic screw cap of sorts but its slightly recessed and difficult to reach.

I did try with a pair of screw drivers, mallet etc but I couldn't do it until I blagged the proper tool from work. It'd probably be an easy one to make I bet. With the tool the swap itself takes literally seconds.

Only further advice I have is, if you do decide to swap the pump, once your ready to do it, pop the bonnet and find the Schrader valve type affair that lives on the fuel rail. Use a cloth and small screw driver to de-pressurise the rail/system then your good to go

Good luck mate if you try it,bit of a gamble I know but its fairly cheap to do and you'll most likely fix your car after the swap

Thanks shaun, I'll order a new pump in the week and fit it the weekend I'll keep you posted.
If this doesn't sort it then it will stay like it lol ive spent enough on it already.