I seem to be having problems with my Punto 75SX (1994).

When I first start it seems to run OK, but then the revs drop and rise again several times.

Once I start driving along the road, its as though somebody is messing about wiv the throttle, in that the power goes for a while then kicks in wiv aggression. Occasionally when I have been driving for some time (engine nicely warmed up), when I pull up to a junction or roundabout, the revs fall to such an extent that the engine sometimes stalls.

The Cylinder Head was skimmed and the Cam Belt changed 8 months ago but all was well until 1 month ago. I have had the Fuel Filter changed, and done the Oil, Oil Filter, Air Filter & Plugs myself, with no change.

Although its running a bit rough, it still returns 43MPG+ (47MPG last week).

Does anybody have some idea what is causing this? As I can't really afford "£ FIAT DEALER PRICES £", but will buy Leads or Coils if this WILL fix it.

Thanks guys and catch up wiv ya soon.
. g1ovh at hotmail dot com .


Looks like none of you surfers/readers and so-called Fiat Friends dont know how to sort out my problem. Guess either your too thick to help, or just too damn rude not to reply merely with some much-needed support.

Oh well it looks as if I dont "Fix It Again Tomorrow" (FIAT), I'll most likely have to try a possibly more reliable "First On Rubbish Dump" (FORD) again!

Oh well thats the fun of owning cars I guess!

sorry m8 i never saw your post till today


what engine size is your punto?

Sorry mate i have only just seen this post, sound like an electrical fault, ECU maybe even the brain, my aunties 1 went on her Bravo and it cost £600 for a new 1, worth getting it checked then if it it that, see if you can get a second hand 1.

The devil made me do it officer

could be air leek. check the ruber seal between air filter housing and throttle body.
post back if it works or not.

Usual things to check are MAP and Lambda sensors.

Would have seen this before if I didn't have such a bad ISP (NTL) as I haven't been able to get on here for days.[!]

Pete.
Cinq sporting 1242cc
Cinqs&Seis Yahoo group
Clubcento

Clean your connections to the sensors, you could try some 10K boost to clean any internal sensors. Also might be worth checking the throttle position sensor.

Im not stupid or rude, Im evil and I have a life outside this forum.

OK guys thanks for all your help, and sorry for the sarcasm.

Donz - for your info the 75SX is a 1242cc engine. Thanks.

Robin - hope the ECU is OK, see below. Thanks.

Dave - Seal is clean and un-damaged. Thanks.

fixitagaintomorrow - Cheers mate, I use NTL and seems like that Worm Virus slowed things down a lot. I have cleaned the contacts on the MAP & Lambda sensors, but no change, see below. Thanks.

Evil-Punto - Cleaned all sensors, no change. Not sure what 10K boost is but I may try some Fuel Injector Cleaner to see what it does. Thanks.

UPDATE - After some electronic testing, it would appear that I was running the car for some time with a dodgy front ignition coil (replaced with a Unipart coil from Partco for £20 ish) so I think the Brain (ECU) has tried to learn the bad characteristics of a Punto with a dodgy coil.
I have tried disconnecting the ECU and leaving that disconnected for some time (2hrs+) and now the car seems to run a bit rough, but more stable (if that makes sense).
I have cleaned the Idle Stepper Motor, with no noticeable change, but that was only last night.
I am going for a long drive over the weekend so will see how it performs then.
I believe the ECU takes some time to 'learn-the-engine' so will see what happens.
Will try to keep you updated but as I have had nearly 12 Migraine's in the last 4 or 5 days it may take me some time.

QUESTION - I am thinking of using some Fuel Injector Cleaner but not sure which to go for. Has anybody got good or bad experiences of Fuel Injector Cleaners, the kind you add to the fuel tank?

Optimax petrol has cleaners built into it.

Dispite what people say, ECUs do not and cannot learn.
They are governed by a set of values which are altered by inputs from the lambda, AFM, temperature, pierburg (if available), and throttle position sensors.

Just a quick response to UK guy Neil, I have a 75 ELX from `94 and it has sufered from strange revving problems, but not a severe as the ones you describe, also a big lack of power at 3-4000 rpm. Sometimes when the engine has been running for around 5 minutes on a hot day, the ECU seems to get confused -its not sure whether the engine is hot or cold and then stalls the engine. My car has suffered a faulty coil in the past, infact it has never been the same since running it effectively on the 2 cylinders for a few miles!
I have taken it to a main dealer, and apart from a £400+ fee (including service) they couldnt find fault, although they acknowledged a "slight hesitation". So I would like to know what you find out.

Quick update:

I have tried Shell Optimax, and my Punto seems a little bit better. It has just sailed through the MOT again, this time with over 100,000 on the 'clock. The only problem the tester encountered was measuring the emissions, as the revs 'rise-n-fall' - 'rise-n-fall' - 'rise-n-fall' all the time (evidently the emissions test requires a steady engine speed). However with some patience he passed it. <yipeeeee>

My question is "has anybody had this before, as the tester thinks it may be the Idle Control Stepper Motor. I am not sure if I should try removing-n-cleaning this or not?"

By the way this Punto is still giving me better than 45 MPG all the time! <amasing>

<blockquote id="quote"> face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Evil-Punto


Despite what people say, ECUs do not and cannot learn.
They are governed by a set of values which are altered by inputs from the lambda, AFM, temperature, pierburg (if available), and throttle position sensors.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

I'm sorry to disagree, but this is not true in the case of smaller Fiats. Other Fiats may differ, but on Cinqs and Puntos (certainly 55, 60 and 75's), the ecu can be 'rebooted' effectively, and from there it needs around 100 miles to pick up it's settings. When you do this, the car runs a little rough and may hesitate a bit, but as the miles go on it smooths out. During this period, the ecu is looking at the engine's sensors to see what the best set of values for fuelling and ignition timing are. It's worth doing if you do engine mods, such as exhausts and filters.

Pete.
Cinq sporting 1242cc
Cinqs&Seis Yahoo group
Clubcento

has it worked right at all since the skimming it might be the ignition coils then mine would hesitate a bit then jump into action after 3000 rpm. it might also be the idle cntrole valve

FixIt - the reason the car will run badly when the ECU has been "reset" is because its memory of "the best way to run the car" has been wiped. It doesn't learn, it knows what the variables are and adjusts things until it gets as close as it can, at this point its stops and uses these figures. If you sell the car, the ECU won't learn the driving style of the new driver, it just remebers the settings for the last one.

Is not "adjusts things until it gets as close as it can" the same as learning?
Or have I missed something along the way??

The ecu does learn the best way to run the car, as you yourself said. The best way will vary with different setups, my 1108 ecu didn't really want to know when I put the 1242 in so I did a 'reboot' and after a couple of days it was all smooth and splutter free. The values it decides on during this learning period are what it uses for reference later on.

I sort of understand what you mean in that the ecu is not a self aware item that can remap itself to any engine, but it does learn. There is only a finite amount it can adjust, and won't optimise like a Superchip.

Pete.
Cinq sporting 1242cc
Cinqs&Seis Yahoo group
Clubcento

I have a Punto 75sx 1995, my Punto has suffered from unstable revving as may of you have. Resentely it failed the emmisions test because the tester could not keep the revs within the specified range.
Anyway to cut a long story short the Lambda sensor was changed, I think thats what it was called anyway, it's the one that sits on the exhaust manifold. Since then it has been like a different car, responsive, smooth, economical, brilliant.

Hope this helps all you fellow sufferers.

Cheers guys. Thanks Tony D for your suggestions. My car has been into Priory Fiat in Godmanchester, who checked the ECU and found no Fault Codes stored. They road-tested the car and reported the same fault as I had described (surprise surprise). Their diagnosis is the Throttle Position Sensor, with the following brief explanation; "....the TP Sensor has failed and so the ECU is trying to adjust the Fuel Injection Pulse Width to compensate for readings from the Lambda Sensor. These readings are delayed and so the car is not able to achieve smooth running. Once the TP Sensor is replaced, the ECU can take a position reading of how wide the Throttle is opened, and any difference is fine-tuned by the readings from the Lambda Sensor....". So my car is booked in for the TP Sensor to be replaced and the ECU/TP Sensor to be re-calibrated. This is going to cost me in the region of £130 ish on Oct 1st so I shall keep you all informed. Thanks to everybody for all your help and advice. Lets hope it is finally going to be sorted.

TP sensors can usally be adjusted is this not true for puntos.

Well well well, what can I say, Fix It Again Tomorrow Garages are all the same. They (Priory Fiat in Godmanchester) have now replaced the TP Sensor, and reported that although the initial fault is now fixed, the Spark-Plug leads are NOT Fix It Again Tomorrow genuine items, and < surprise surprise > the leads are arch'ing' to the Crank Case. So they now suggest the leads should be replaced, but at £45:00 + VAT I think not. I bought these leads from Halfords on the 14th September, and fitted them on the 15th September, that was before the Original Diagnosis by Prior Fiat on 17th September. So what else can I say. I shall look at these leads this evening (in darkness) and if they are arch'ing' then I will try to re-route (with engine off), or fit the Original Fix It Again Tomorrow leads.
Let you know what happens.

Last night I checked the leads, <wo ho ho no sparks> but just in case, I re-fitted my original Fiat leads. At the same time I cleaned & checked my plugs, still looking good with a gap of 0.9mm as required. Dont get me wrong the car is running a bit better, but it is hesitant. Not running as smooth as it used to be, but at 102,000mls what should I expect. Well -erm- after speaking face-2-face with other Punto drivers I meet in Car Parks (and no I dont make a habit of it) seems they are all usually pretty good. So I have dusted off the cobwebs and dug deep, I now have on order an Ecotek CB26-P to try.
Will let you know how it goes.