I,m investigating a problem on a Punto Sporting 1.2 16v(old model - 98). It starts and runs a tickover perfectly on all four cylinders. If you floor the throttle (at rest or on the move) it seems to drop to two cylinders(yes two - not three!). As soon as you back off the throttle all is then well.
Leads and plugs have been renewed, seemed to slightly improve but not cure the problem. If its damp the problem is worse, so I think it sounds like some sort of HT problem? The only thing left on the HT side is the coil pack - which interestingly looks as though its split up into pairs of cylinders. or is it the msin CPU.
Any suggestions before many GBP are invested in expensive coil packs and CPU's.
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Coil Pack - double-ended wasted spark type....this fits in with the fault you describe.
Replace the coil(s) and all should be well, I reckon!
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groups.msn.com/honestjohn - Pictures say a thousand words.....
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Thanks, one coil pack coming up. Are they very very expensive?
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Not sure, being honest.
FYI, 1998 Range Rover 4.6 V8 ones are horrendously expensive - the last one I replaced was over £330+VAT
I'm sure yours will be far more sensibly priced John. I would expect it to be <£60 or thereabouts.
The way in which you describe the misfire ["As soon as you back off the throttle all is then well"] smacks of HT problems. In addition, you have noticed a slight improvement; that almost confirms it for me.
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groups.msn.com/honestjohn - Pictures say a thousand words.....
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Agree it is probably the wasted spark coil pack.
My first Vectra V6 also had wasted spark coil packs, and one of them packed up soon after new delivery of the car.
Every time more than half throttle was used once everything had warmed through, the engine lapsed on to four cylinders. If the engine was cold or half warm, no misfire occurred. When the pack was replaced, the problem was sorted, never to reoccur in three years of then utterly reliable tenureship. I guess internal coil insulation was breaking down.
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Coil failures VERY common on Fiats with the twin coil packs. Last one I bought was not for a 16v, but I am pretty sure they are all the same. Fiat No.46548037 @£42.74 + VAT. If the problem only occurs on load you may have no option but to change both. If fault can be induced at kerbside you may be able to identify which one it is by alternately disconnecting the primary connection plug. DO NOT try to test by removing HT leads with engine running - you may then damage ECU.
Unfortunately, I have seen a couple of cars where the fault was in fact a loss of primary signal from the ECU. To test for this you need an oscilloscope hooked (to the primary signal at each coil in turn) up when the fault occurs.
Regards, Adam
Whatever is rightly done, however humble, is noble.
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Thanks for the replies,
Replacing the coil pack restored normal service!
PS The one on ErIndoor's Punto 1.216V HLX looks very different.
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