Hello all,

My 1.2 Active Sport 8v ('52' plate) had the engine light come on a few days back. I OBD'd out a P0120 and cleared to see if it would return. It did after a night's rest and maybe 10 miles of drive.

I noticed that with about 45 minutes of urban driving the light went out again on its own but after a half hour rest the light returned and stayed on for the drive home.

When I start up and I'm idling, the revs go up and down on its own roughly every second, so getting the car rolling from cold can be a little laborious but seems to behave a little better the higher the gear. In 3rd I'll get an occasional lack of power and have to floor the accelerator momentarily or change down to 2nd.

Obviously this isn't ideal to drive and I've kept it off-road since Monday evening but will have tinkering time tomorrow afternoon and Saturday.

I've seen online that the P0120 is to do with "Throttle/Pedal Position Sensor/Switch "A" Circuit Malfunction" but not sure if my explanation could help you guys narrow down the cause.

I bought the car 2 months ago from a trader on auto trader and have been told by other people that there is a 3 month warranty for 'traders' but I've already been back to the guy to repair the head gasket, coolant thermostat, and starter motor...

I am New to motoring, having passed my test last April, but have learnt so much in this short space of time (mostly from loitering in these forums!) and would like to attempt more of my own repairs.

Please see below a list of what I've done / had done so far:

Ht leads
Head gasket
Bonnet release cable
Starter motor
Thermostat
Coolant flush
New bolts fitted to air filter box as it had a tendency to jump off the TB inlet

I hope I've listed everything of relevance but please do let me know if further information or diagnostic results are required.

Unfortunately my obd scanner isn't a usb jobbie, just a handheld that displays and can clear codes

I've had a scan of the net and found I can get a whole TB unit from breakers for £30-40 delivered but would rather do a repair if possible. Money is a little thin on the ground at the moment

Since the 8v is a Cable engine

There is 2 sensor on the throttle body

ICA (idle control actuator)
And the
TPS - Throttle position sensor
Which is the bit that knows how open the butterfly valve actually is

If you've got your foot down - it want to know that, so it can ensure with other sensors readings that its going to mix the correct fuel

If the sensor is plugged in tightly
And the connection is clean and good
The wiring isn't damaged in anyway, its probably a case of a dead/dying sensor

Not to worry
The throttle body is actually a DIY job

A decent set of allen keys and spanners you'll be fine

Something like this off ebay would be ideal
http://www.ebay.co.uk/itm/FIAT-LANC...arts_Vehicles_CarParts_SM&hash=item3cd34e7580

Airbox off
Battery disconnected
2 multi plugs on left
Throttle cable clip
Disconnect throttle cable
2x Bolts holding the engine ECU into place
3x Bolts holding throttle body down

Refitting is the reverse of removal

If you look the guides section about cleaning the throttle body - its pretty much that you are doing

i dont think a clean is needed, but if the throttle body is gunked up, try a bit of elbow grease first

Ziggy

Thanks for the rapid reply.

I think I'll try cleaning it up a bit first.

Is there anything special I need to do in re-fitting the throttle cable or just put it back where it came from? I don't want to snap any more cables because getting that bonnet release through the bulkhead was a pig.

Going by previous MOTs the car has lived most of it's life by the coast so the salty air can't have helped.

I will take some before and after pictures and give another driving report tomorrow afternoon or Saturday.

Thanks again for the quick reply and the pointer towards the guides for cleaning

Dan

Have you tried a throttle/peddle reset.

I think its. Put key into ignition turn to mar/don't start it.
Leave for 90 seconds.

Turn off.
Then put back on for 90 seconds then start the engine the go for a slow or fast drive
The car then is supposed to go into a learning process.

Feck knows if it works like-but I've heard of mechanics do it after doing work on fiats/Alfas .

Thanks, oldhammer. I'll do this after I've had the TB out cleaned and reinserted

But isnt that process on for fly by wire tgrottle bodies
8v is just a cable

Ziggy

I'd be inclined to look for any obvious wiring issues. If none found, grab another complete TB from a scrappy, clean, fit, clear code and say a quick prayer to the God of Small Cars.

I've taken out the TB now and cleaned it up. Please see pics



And after



I've used ear bud cotton sticks to dry out the pin connections and found there was what looked like a little corrosion in the 3 pin connector. This looks to have cleaned out ok.

The black unit that the 4 pin connector goes into though has like a cave inside the TB which is still pretty dirty and is taking ages to dry.

I've left it hanging on the line to let this freak British sun dry it out before connecting everything back in but will update you all after.

I noticed that when removing the air box, the top left (looking from the front of the car) screw/nut was missing. Could this be allowing unfiltered air through the intake, and would this aggravate/cause this problem?

I mentioned in another thread that I was thinking of upgrading the intake but will definitely do this if the missing nut is going to be a problem.

Thanks,

Dan

Got it all fit back in and was idling high without the air box on but not jumping revs. Installed air box and the revs idles at normal (900ish?)

I applied steady pressure to the accelerator with my hand and found that holding at 2.5k revs reproduced the auto-revving thing again

I tried a quick drive around a couple of back roads (literally a 2 minute drive) after letting the car warm up at idle on my drive, although the fan didn't spin up during or after the drive.

The drive was fairly similar to when this issue appeared first, just seemed to be present at a higher rev count.

Tried re-seating the ECU connectors (so I could inspect for water damage too) but no problems or change to how the car is revving as explained above.

I'd like to rule out any diy jobbies before either buying a replacement TB / talking with the trader to see if he can do it. I like this car and don't want to have to get a refund

Can the Throttle Position Sensor (I'm guessing the unit with the 4 pin connector within the TB) be replaced independently to the entire TB?

If not, is there any specific range of voltages I should be able to read, and which wires will I need to read from?

Sorry for the super specific questions, I'm in pc repair by trade and finding car repair similarly enjoyable.

Dan

My guess is that if you walked into a scrappy (rather than used eBay) you'd get a new TB for 15 quid. The MPI Seicento TB is probably (check with ePer) the same. The sensors certainly are.

Yep, stuff can be replaced independently of the TB. You may be able to find the nominal values in the Punto factory manual (check classifieds).

Remember that these things live in a much more hostile environment than PCs, so relatively aggressive cleaning (maybe one of those little glass fibre pencils) and silicone grease are your friends.

Took a drive (in my dad's car) to a breakers this morning and picked up a used TB and cleaned it up. Had to leave it to this eve to fit due to other commitments but got it all cleaned up and swapped over with mine.

Glad to say it worked a treat and idles much quieter (at about 825 rpm - is this normal?)

Pressure on the accelerator by hand held steady at 1k, 2k, 3k rpm and even sounded healthier, but this may just be me hearing what I want to hear.

Filled with confidence (and manflu) I took a drive (to the supermarket for sinutab) and am really happy with how it's driving. It feels smoother, much more responsive, and I no longer have to fight against it to do what I want it to do.

Being happy with it, I took her to get a drive through wash, although I'll do that by hand next time.

The MIL turned itself off after a minute or so when testing revs as above. I'll update with how it's running in a week or so.

Another off-thread question, what is the thing called for the passenger door that holds it open at certain points? It's been brought to my attention that mine doesn't work!

Thanks to all who've helped in this thread

LonDan;3283666 said:

Another off-thread question, what is the thing called for the passenger door that holds it open at certain points?

Click to expand...

Check strap! Just replaced my front ones, as they creaked like crazy. Nearly £30 a pop, though, from Big Mick at Eurocarcare.net.

PS: Hope you're feeling better, soon...!

Excellent, thanks. Watched one on eBay. Will order on pay day

Quick update on this, still running fine aside from another issue but I've another thread open for that. No more jumpy idling thus far.