Technical Stilo throttle problem?

[richnight]

I would really apreciate some help with this prolem, Stilo is PERFECT 90% of the time... but the other 10% of the time its really irritating. First let me describe the problem and then what i have dont about it (to no avail):

When pulling away particularly in traffic throttle responce is flat and then jumps up to 2000 rmp, sometimes then just dies out but doesnt stall making it kangeroo... it does this fairly regularly!

When reversing the car kangeroos all the time unless i give it loads of revs, again a bit embarassing if there is anyone close by!

I have:

Had the car serviced - oil, filters, plugs, drain and refill coolant.

Cleaned the throttle body (using WD40 and a toothbrush and cleaned up with cloth after)/

Changed the battery today after leaving the ECU unhooked all night.

Cleaned the D4 at the same time as above with electrical contact cleaner.

Like i say otherwise car runs perfectly and some days it will sit at 1500 rpm quite hapilly with little pressure on the throttle but others its 800 or 2000 and nothing in the middle : (

Well i hope someone can give me some more ideas because i think i have exhausted my mechaniacal know how!

Thanks,

Richard.

 

[Deckchair5]

What engine is it?
Do you get any engine warnings?
Have you read any fault codes?
Has it always done this since you bought it?
Any work done recently apart from filters, plugs etc?
Is the warm tickover (air con off) rock steady? and what rpm?
Is it worse/ better when engine is cold?
Does engine still falter if you put gas on with car stationary?

 

[richnight]

Thanks for the quick reply, sorry I forgot to give the most important information, its a 1.6 3 door Dynamic 2002. I have had the car for 3 months and its always done it, recently I took it for fiat for a service and they advised that the throttle body/MAP sensor needed cleaning but wanted an hours labour to do it, seeing the guide on here I thought I'd have a go and it looks clean to me now, i used an old toothbrush to get aroud the back of the lip as well. I have never seen the engine management light come on apart from when it lights all the lamps on ignition.

Tickover is rock steady all the time but sometimes drips a little if left idle for a long time, but warm or cold doesnt seems to make must dfference.

Interesting your last point, when stationary the throttle is always perfect, if i want to set 1250 rmp i can do it, proble seems worst when stopping or starting or picking up from very low speeds.

Thansk again!

 

[Deckchair5]

Do you have a fault code reader? If not then I would get something where you can read and clear stored codes

Difficult really to diagnose so more info always helps.

MIXTURE
Kangarooing whilst reversing sounds like very wrong air/fuel mixture. What's your av mpg figures?

ENGINE TEMP SENSOR
Engine temp sensor can make it overfuel so does it start well when hot or cold starting? Maybe check eng temp sensor resistances as per Stilo Guides

MAP SENSOR
MAP sensor circuit fault code stored can make it accelerate poorly and will give awful mpg, shouldn't affect slow speed reversing though


THROTTLE INPUT AND RESPONSE

Obviously gas pedal input and throttle valve response should act like a mirror. A problem at the gas pedal potentiometers would cause erratic response. Here's mine showing nicely mirrored response from 5-10% gas pedal input
If yours feels the same as this when stationary ie rpm accurately following gas pedal then gas pedal input must be ok but if it feels nothing like that when you're moving under load then it sounds like incorrect air/fuel mixture
so to start with i'd check No.1 lambda output, eng temp sensor, contact cleaner on MAP sesnor connector and clear MAP sensor fault code if one is stored and reset ECU

Did they experience the hesitation when it was at the Fiat garage being seviced? Why did they suggest cleaning the MAP sensor? Was a MAP fault code stored?

 

[richnight]

Thanks again for your reply, the thought occurred to me that it could the the reostat on the pedal but as I understand they are pretty solid and dont give much trouble but if its simple to swap it out then it might be worth a look.

I will test the engine temp sensor and clean the MAP connecter as you suggested, Lamda is good I hope! it looks new and connectors are nice and shiney - I will try changing this last! emissions were fine on its MOT in November.

I am not entirely sure what MPG should be on the 1.6 but I reset it for the 50 mile journey between Chelmsford and London (so motorway and a bit of traffic thrown in) and it returned 44.3 average - and that was normal driving around 70ish. if I drive around town it usually drops to about 35 mpg.

Regarding the MAP, can I confirm that it is on the back of the plastic inlet manifold? to the left of the throttle body if you look at it from the front? Also if the MAP is faulty and its replaced with a good one will the ECU detect this and start reading its values again or does it need to be cleared with examiner?

Thanks,

Richard.

 

[Deckchair5]

Here's your MAP

It seems to need the fault code clearing before it will accept a new MAP sensor but they rarley go wrong themselves. More often the connections tarnish and return out of limit voltages and the ecu ignores the MAP from then on as long as that fault code stays stored

Av mpg sounds good

 

[richnight]

Ok thanks - sounds like time to get the contact cleaner out again and then buy a fault code reader... does anyone know if the U280 will clear the fault - there are loads of them on ebay for about £30 which sound spretty reasonable.

Actually before I do that, if there was a code stored for Faulty MAP would my Engine Management light be on? I have no warnings at all.