I have mentioned this before but the symptom are becoming a bit clearer now.

The car still seems to be idling too high at junctions, as if it is running from cold start all the time, I only do short journeys but even after 5 miles the idle seems to be around 1300rpm (there is no rev counter so I am just going by ear).

I revved it at idle and when the I released the throttle it idles higher than it did before it I revved it. This afternoon the engine cut out on me, now it might have just been me, but my foot was on the clutch at the time so I can't see how it could have been.

Could this be a fault with the throttle position sensor? The cable from what I can tell seems to operate an actuator which then has a variable resistor which then tells the value how much to open and close. Is this right?

In normal driving conditions the engine is perfectly smooth.

No ECU light has come on and it is a 2010 Panda Active 1.1 Eco.

Ours is a 59 plate 1.1 and has done the exact same in the past. As you say no tacho but audibily higher note sitting at idle, fuel economy drops through the floor and if you turn the car off it also runs on a for few seconds before juddering to a stop. Restarting, and 9 times out of 10 it "resets" itself back to normal.
No idea why and when it did it under warranty Fiat main dealer couldn't find anything in the ECU logs. Happened more frequently in damp weather. After liberally coating all the electrics under the bonnet about every 4 months, it appears to have gone away this year but could be coincedence.

Edited to add, that ours also cut out on us twice whilst coasting up to roundabouts with the clutch fully in ahilst it was having one of these moments, so it's not you, it is the car.........

I don't like the sound of that, nothing worse than those faults that are impossible to diagnose.

What do you mean by coat the electrics? Put some sort of grease on the terminals?

The throttle position sensor (TPS) is a dual track potentiometer. The ECU compares the voltage from the wiper of each of the pots and sets a fault code if they differ significantly. I think it's unlikely to be the TPS itself but the electrical connectors are known to cause odd problems occasionally. Try unplugging/replugging the TPS connector and also give the electrical contacts a spray with some electrical solvent cleaner. Do the same with the other adjacent connectors on the throttle body.

High revving at idle can be caused by a leak in the inlet manifold. Check that the air filter housing is properly seated and also the small hose that is attached to the back of it.

Thanks, I am not that good with mechanics, I fix computers for a living and I understand how modern car engines work and what all the sensors do I am just useless at the spannering bit I did correctly diagnose and replace a faulty MAF sensor on my old Corsa though.

I assume I should disconnect the battery before unplugging the TPS? I did suspect an air leak so did check the hoses and they all looked fine, I will check the air filter housing though.

I just hope it is nothing serious and I would be extremely annoyed if it is because I have mentioned this issue twice when the car was under warranty, first time they replaced the manifold hose (from the engine block to the rigid exhaust) and the second time they fobbed me off saying it will be noisy because it is a cheap small car (e.g lack of sound proofing).

There is noisy, and there is sounding like a bus at idle.

I've had this recently, there's a cure, but you need to take your pick of the things I tried!

It started cutting out over bumps, that stopped, but the idle started playing up.

Started normally with the high rpm. (usual very fast idle just after cold start)

Within a minute the rpms dropped a little (usual fast idle)

Drive off and after a couple of minutes the idle dropped to normal warm idle (750 ish rpm)

After two miles, pull up at the lights and it was back to the fast idle!

Turn off, restart and it would be ok until the next cold start, where it would repeat the performance.
MPG was awful, and it felt a bit chuggy.

I cleaned the throttle body, including idle control valve, no different.
Cleaned the ECU connections, including the earths from it to the body, fuse box to body, no difference.

Thumped the ECU (yes, thumped with fist!), this stopped the high idle, until next cold start.

Scanned the ECU, had P0130 pending, upstream (pre cat) O2 sensor circuit malfunction.
I also noticed from a cold start the car wouldn't enter Closed loop as it warmed up but went from Open loop (usual from a cold start) to Open loop - system fault.
Only when the car was warm and the engine restarted did it enter closed loop.

All the other sensors seemed to be functioning, TPS, ECT, Crank, Cam etc.

I logged the upstream sensor switching and it appeared ok, switching between 0.1 and 0.8 or 0.9v, back and forth, once every second at 2000 rpm.

I pulled it out and tested it in a flame, it seemed to be working fine, 0.9 in the flame, dropping immediately to 0.1 out, then 0.0 when it cooled off.

I had a new one on the shelf, so fitted it and it seemed to sort the open loop system fault and it seemed to idle ok.

At that time I was convinced it was the heater circuit of the upstream O2 that was slow, so it wasn't preheating fast enough.
The ECT must have been reporting the car was warm enough to enter closed loop, but the O2 wasn't at temp and switching quick enough, hence the Open loop - system fault at that time.

I considered once the car had been driven, turn off and back on again, the fault cleared and the O2 must have been heated by the exhaust gases to operate normally.


Only after all this did I notice the trace from the downstream (post cat) O2.

Information about what it should read is a little hard to find.
Information on what is actually does is even more confusing, but don't believe it does nothing but check the cat, it does have some effect on fuel trim if it thinks the cat might be damaged.

It should NOT copy the upstream sensor, ie switch voltage up and down quickly (knackered cat)
From working out how a cat works, (it stores and uses air to burn off nasties), I predicted it should return a pretty even voltage around the 0.45v which is perfect fuel trim (or slightly more when cold).
Only dropping when the cat really heats/ engine leans up (over run) where it reads a really low voltage.
If the engine is left to idle, it should slowly start to rise again over a couple of minutes.

Mine was flat lining at 0.1 volt and nothing would tempt it to move!

I pulled it out, replaced it with the suspect one I removed from the upstream and the car in now back to normal and the down stream sensor trace seems to report something more like I'd expect (0.6 v idle, down to 0.1 or 0.2v on the over run, then climbs back to 0.5ish volts)

Starts, idles, runs perfect, mpg back to normal.

So I'd suggest checking the O2's, both of them.

By 02 do you mean lamdba sensors?

All of that looks a bit beyond me! I fear I may have to take it to my local indie who is very good at the ECU side of things. The car has only done 15,000 miles so I am a bit mad that something so difficult to cure may be up with it already.

What I will say is the idle is always steady, it is always too high, it doesn't seem to change other than when I revved it that time, so I do wonder if it could be a simple mechanical fault such as a split hose.

The engine does sound a bit tappety too on idle.

Yes, Lambda, O2, Hego, they're all the same thing.

There are two sides to a modern O2, the heater side.
Older sensors didn't have this element, so relied on the gases to heat it up, which took time/produced more emissions.
The modern one pre heats, voltage (battery voltage) for this comes striaght from the fuse board, so it can start working sooner.

Failure to pre heat will keep the car in a cold start fueling trim (Open loop with a fault)

The sensor side, this doesn't need voltage to work, it actually produces volts depending on how hot the exhaust gases are.
This exhaust heat will alter depending of the condition of the fuel trim, rich or lean.
When the car goes from the cold start Open loop into Closed loop, this is when the sensor starts to work (or rather the ECU starts using the data from it) and uses the O2's data to trim or switch the fueling back and forth to try and get perfect fueling, which is around 14 parts air to 1 part fuel, or what's referred to as [ame="http://en.wikipedia.org/wiki/Stoichiometric"]stoichiometric[/ame]

This switching can be seen when logging the O2 data, hold the rpm at around 2000 rpm and the volts should wave up and down bewteen 0.1v and 0.8 or 0.9 volts.
The middle of the wave form (half way between upper and lower readings) should be around 0.45v which is close enough to stoichiometric.

Failure of this side can lead to the volts not switching up and down or not switching up and down fast enough, it should switch (cross count) around once a second or a little under.
Either will send incorrect or "unbelieveable" data to the ECU, which it tries to fix at first, if it reports lean, it richens the mix up and vice versa.
When it fails to achieve a believeable signal (or can't get a quick cross count), it reverts to a fail safe, which it the Open loop (with a fault).

Apart from cold starting and first few seconds of warm up, the only other time Open loop is used is snap/wide open throttle, but after it should revert to Closed loop again.

For around £8, you can get a Bluetooth Obd2 mini adapter/reader from Ebay. It works with either a laptop or Android device, so your tablet or smartphone, it should come with (limited) software for PC.
(Torque Pro is a simple App for your phone/tablet and works with my 1.1 Active)

It'll read enough sensor data of the engines ECU to hopefully narrow down what's wrong.
Throttle postion, engine sensor temp, fuel trims, O2 data etc
You'll also get to teach yourself OBD2 along the way (don't worry, the 'net and me can help)

BTW, mine sounded as if something down the back of the engine, near the alternator was ticking or rattling when it acted up with the fast idle.
It stopped after sorting the O2's, must have been something like pre detonation (pinking) or knock due to the fuel trim being way off.

Thanks I will get one of those diagnostic things.

It does certainly sound like the car is constantly running cold, it is if the choke is constantly out on old carburettor car.

If it is just the lamdba and it solved it fair enough, but once I start the route of part swapping to try and solve the problem I think it is man maths time but I really don't want to buy another new car.

Stick with it, it still runs doesn't it?
With a cheap tool I can walk you through a few checks, see if we can pin point the issue.

You could try swapping the upstream and downstream O2's over and see if it starts running properly.
They are exactly the same part, length of cable etc and really costs just a bit of time (and a socket)
If I didn't have the one sitting on a shelf, that's what I would have done first.

The upstream has the influence over the short term fuel trim.

The downstream monitors the Cat's efficency.

So moving a suspect one into the downstream position may flag a downstream related code, but it should not effect the cars' short term fuel trim or running/idle and may help identify if one has a problem.

They are easy to get at, I got the upstream out from under the bonnet, though the downstream needed the car up a bit to get a good swing on my breaker bar.
A special O2 socket like this is recommended as a normal won't fit over the body/wiring and as mentioned a breaker bar as they can be in fairly tight.
http://www.ebay.co.uk/itm/like/231004011175?limghlpsr=true&lpid=102&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0&ff12=67&ff13=80&ff14=102&ff19=0
You local Halfrauds or motorfactors will stock them.

You know your stuff Mr Goudrons - top info. O2s on the Fure engine are pretty critical and I have eaten through a few during my supercharging project, so if in doubt, replace.

Hope the issue gets fixed soon. I still get top he occasional high and wavy idle myself, so I may yet have to bag me a couple more.....

Thanks I will probably get my indie to it because he will probably charge as much as what the tool would cost anyway. He is very fair like that but then he has been looking our cars for years until we both got new cars.

Does the brand of the lamdba sensor matter? They seem to vary from £16 to £90. A Bosch one is £70 and if I was 100% sure it would solve the problem I would I am happy to spend a lot.

I did about 15 miles in it yesterday and it ran well, still rough at idle but I blasted it up a hill as a test and it didn't miss a beat.

I will buy a one of those blue tooth scanners (what app I need to download?) but probably wait till the service in April before I get the repair done unless the diagnostics clearly show a problem.

After reading all the posts, i'm too going down the Lambda route. Does anyone know the part number for the 1.1 as i can only find it for the 1.2 ( is it the same part ? ) and there appears to be two differing cable lengths - 325mm and 430mm ?

I got a NGK one, but they are branded NTK.
From here
http://www.sparkplugs.co.uk/
Was around £50 odd.

I think pre and post 2005 cars are different sensors.

Cross reference 1.1 and 1.2, but I think they are the same (depending on year)

JD82 said:

I will buy a one of those blue tooth scanners (what app I need to download?) but probably wait till the service in April before I get the repair done unless the diagnostics clearly show a problem.

Click to expand...

Torque Pro.
https://play.google.com/store/apps/details?id=org.prowl.torque&hl=en_GB
http://torque-bhp.com/

It should come with it on the disc, if not, try Google Play or drop me a PM, I can sort you a copy.