Technical Hesitation around 2000rpm

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Technical Hesitation around 2000rpm

Punto1cab

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Punto 16v 1.2 Cabrio. 50,000miles. At around 2000rpm it has developed a bit of a splutter, particularly under load. As it is a pre 2000 car there is no diagnostic socket, so it is back to basics. Any ideas where to start? I don't think it is dirty fuel - but is there a filter? If so where? & cleanly right up the rev range.David
 
yep, and some software - IAW-Scan2 or MultiEcuScan.

I always had issues getting IAW-Scan2 to work properly with the 16v ecu but free version of MultiEcuScan will read and clear codes and let you view all the sensors and log (upto 4 different things with the free version iirc). Google search will bring up both bits of software.

But that won't be all that useful unless you have actually had the engine management light come on.

Bit of a splutter could be alot of things though - is it always the same or on and off issue? is it at all worse when warm? has it been getting progressively worse or just started and stayed the same?
 
Took me ages to get my iaw scan working because the vag-com to usb leads are such patchy quality (it took me 4 goes to get one that finally worked)

The most important thing is that the vag com cable has the ft232 chip in it because it won't support the baud rate the Fiat ecu puts out otherwise.

As for fixing the issue, i'd start with the most basic of basics, plugs and leads and coil packs (or at very least run the engine in the dark and watch for any arcing), from there with new plugs and knowing leads and packs were at very least ok.
 
Thanks to you all for that. A quick check on HT leads shows no corrosion or obvious problem. Looking at in the dark is a neat idea! I'll check & see how old the plugs are as well. Can the coil packs be checked on basic electronic measuring equipment? ie what sort of readings are to be expected.
I'd give it an "Italian tune up" down the road at 6000 rpm for a mile or so, but not until the cam belt is done!
No warning lights have come on by the way
David
 
The fault is there, hot or cold & has only recently (50miles) appeared. Spark plugs last changed in 2010 with coil packs & leads. About 12000 miles ago.
D
 
Mmmm, if it has new(ish) plugs, leads and coils. I'd lean towards crank sensor dying maybe. They tend to get worse with temperature but thats not always the case, just common, I even had one that did the opposite - really had and spluttery when first started and cleared up.
These often don't report a fault in the ecu and if they do they just report a misfire rather than the sensor itself - i think if it completely failed and went open circuit it might flag up but i have never seen that happen on a FIRE engine.
Cheap as chips from S4P atm... https://www.shop4parts.co.uk/?name=store&op=Details&ProdID=828&sku=72819

Took me ages to get my iaw scan working because the vag-com to usb leads are such patchy quality (it took me 4 goes to get one that finally worked)

The most important thing is that the vag com cable has the ft232 chip in it because it won't support the baud rate the Fiat ecu puts out otherwise.
Bizarrely for me its not my cables, I can try plugging it in and it just didn't connecct with IAW Scan, but i could close that and open MES without touching the cables and it always worked - no idea why, perhaps it was just an issue with my particular ecu. I don't have it anymore so who knows, i just used MES on the 16v and it just worked so never really bothered trying to get IAW Scan the work properly.
 
Mmmm, if it has new(ish) plugs, leads and coils. I'd lean towards crank sensor dying maybe. They tend to get worse with temperature but thats not always the case, just common, I even had one that did the opposite - really had and spluttery when first started and cleared up.
These often don't report a fault in the ecu and if they do they just report a misfire rather than the sensor itself - i think if it completely failed and went open circuit it might flag up but i have never seen that happen on a FIRE engine.
Cheap as chips from S4P atm... https://www.shop4parts.co.uk/?name=store&op=Details&ProdID=828&sku=72819


Bizarrely for me its not my cables, I can try plugging it in and it just didn't connecct with IAW Scan, but i could close that and open MES without touching the cables and it always worked - no idea why, perhaps it was just an issue with my particular ecu. I don't have it anymore so who knows, i just used MES on the 16v and it just worked so never really bothered trying to get IAW Scan the work properly.
Trying a new pair of coils first
Will post how it gets on
DavidH
 
Trying a new pair of coils first
Will post how it gets on
DavidH
New development!!
Coil Packs arrived & as they did so I noticed the injector warning light making an occasional appearance. If I made it hesitate (under 2k revs in higher than necessary gear), revving makes it go away.
So in with a bottle of injector cleaner & see what happens. I don't want to be replacing injectors at £100 a go!
David
 
Result!
New belt/water pump & two coils etc fitted by local garage. Car rejuvenated!
Everyone happy!
Thanks for advice out there
David
 
Result!
New belt/water pump & two coils etc fitted by local garage. Car rejuvenated!
Everyone happy!
Thanks for advice out there
David
AARGH! A definite splutter yesterday & with "injector" light briefly on!
Won't panic until the tank has used Wynn's magic jollop. Mrs H hasn't yet noticed!
Runs smoothly up to (& beyond!) 6500rpm though!
D
 
i still think very early signs of crank sensor on way out is prime suspect - it all sounds like that to me, occasional misses without EML for a while, then them becoming more frequent over time and then EML starting to flash is exactly what happens, so cheap and quick to change it seems silly to not try it in my view... under £20, one bolt and one connector.
 
i still think very early signs of crank sensor on way out is prime suspect - it all sounds like that to me, occasional misses without EML for a while, then them becoming more frequent over time and then EML starting to flash is exactly what happens, so cheap and quick to change it seems silly to not try it in my view... under £20, one bolt and one connector.
Sound advice I think! I'll let you know...won't be for a week or so though!
D
 
i still think very early signs of crank sensor on way out is prime suspect - it all sounds like that to me, occasional misses without EML for a while, then them becoming more frequent over time and then EML starting to flash is exactly what happens, so cheap and quick to change it seems silly to not try it in my view... under £20, one bolt and one connector.


The "problem" is still around, but not so obvious. I'll get a crank sensor & when I get around to it (!) fit it. Or it will sit on the shelf with the other bargain bits! (wiper blades, spare antenna, rear exhaust system.....
Thanks for your help
David
 
i still think very early signs of crank sensor on way out is prime suspect - it all sounds like that to me, occasional misses without EML for a while, then them becoming more frequent over time and then EML starting to flash is exactly what happens, so cheap and quick to change it seems silly to not try it in my view... under £20, one bolt and one connector.
Bought a genuine Marelli crank sensor (as you say about £20!)
Where does it fit? I have peered around the engine & cannot see anything likely ( & I am a reasonable DIY mechanic!). Front/back/top/bottom!
Any advice welcomed
D
 
attachment.php

https://www.fiatforum.com/punto-mk2...erything-1242cc-fire-engine-2000-onwards.html
 
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