Technical Flat spot and trouble starting

[Mikey_P_HGT]

Just joined the site, i have been looking on here for a few days now searching everything i can think of relevant to my problem to no avail specifically,

I have recently taken ownership of a 2001 punto hgt, and my problem is wen i start the car, cold or warm it takes anywhere between 5 and 10 seconds to turn over, sometimes i need to press the accelerator sometimes not, then sometimes when approaching say a junction and i have the clutch down and stop it has cut out of its own accord, so my first question is, what factors can cause this? the second part which i dont know is connected to the first issue is, in 2nd 3rd and 4th and maybe 5th gear, wen accelerating hard at 3200 rpm - 3800 rpm i have like a flatspot, il put my foot down at low revs and it will go rapidly but when it reaches these rpm's it steadys out acceleration wise and then begins to accelerate again, hot or cold it does not matter, i have asked and asked people around me what they think it can be and i am having all sorts of answers, plugs, ht leads, coil pack ecu, i have not changed anything yet until i know or pinpoint what it is more than likely to be, any help guys would be appreciated, if u need more info jus ask ive tried to cover everything, thanks, Mike

 

[ktmmark]

Possable temp sender to the ecu, giving incorrect temp causing poor fueling
(not the one for the temp guage)

 

[Mikey_P_HGT]

How would i go about checking this or repairing it? any way of resetting it?

 

[ktmmark]

Need diagnostics to see what the ecu is reading, but you could diconnect it & see if it runs any different at a push

 

[Mikey_P_HGT]

another guess of a mate of mine who works in a merc garage, he says it could be the crank sensor, any truth in this? - its not a huge problem it runs fine anyway but its always in the back of my head, so im constantly watching for problems when i drive.... arghh lol

 

[ktmmark]

Poor starting & flat spot i would look @ fueling i.e if the temp sender tells the ecu the engine is warm when it,s not you will not get enough fuel ,see it on astra's quite a lot
M.A.F /M.A.P/ lambda & Temp sensors are all used to calculate fuel required thats why you could do with it connected to a computer it could be any one, even an air leak on the inlet side making it run lean

 

[Turracan]

i have this exact problem now and its getting worse... did you fix it and if so how? thanks

 

[Mikey_P_HGT]

soo far i have nothing to report, the problem is still ongoing and i duno if its me looking into it too much but it does seem to be getting worse, the mechanic i bought it off is due to "pop down" anytime now i explained the problems and he seems to think its fuel related/ injection, but also i have noticed that my back box on the exhaust is rusted up to the max, and the fluttering noise i hear at the flat spot "may" have something to do with this, im thinking if there is a hole there then obviously performance will drop because of the back pressure? im just guessing here though, but again thats one of a million ideas spinning round my head but until i see this guy i cant say for def what it is, whats ur car like in general? did it just one day have this flat spot? or over time? u changed anything on it and then this occured? my problem came with the car so i couldnt say what caused it, i have noticed though, on a very cold morning i can start it first turn of the key because the idle is right up over by 1100 ish, but when warm then i notice the problems more frequent so then im thinking the heat is affecting sensors etc so i really dont know, as soon as i know anything il put it here for future reference anyway!

 

[Turracan]

it all started after i installed central locking, but i cant see how that would affect it. i think its my temp sensor on its way out, because my temp warning light comes on even when its cold and then the injection light, and i think this is starving the engine of fuel at startup because it think its really hot so gives it less fuel, now after about 5 mins of driving the lights goes off and it starts to run perfect because i think the engine just starts to ignore that sensor because its talking crap.

i might just replace it, because they are only about £13. if its not, i aint got a clue it could be anything!

 

[Mikey_P_HGT]

well funny u should mention about the temp sensor, just now no longer than 20 effing minutes ago in the pouring rain my car stalled at the lights and refused to start, abs light key code light engine management and max temp light, tried starting wouldnt recognise the key, then it did but then it was displaying the engine had no heat and the max temp light came on, then engine managment light came on etc etc i have only had it 3 weeks ish and im thinking its more hassle than its worth, i got no choice but to take it in 2moro, and like i said before, anything that i find out i will post on here...

*edit... as for the central locking since ive had the car and only one key the button on my key i presume is for the central locking, but since ownership it has never worked, i duno if its broke or disconnected! i think the mechanic knows more than hes letting on!!

 

[Turracan]

just replaced the coolant temp sensor, but hasn't fixed the problem. no change at all.

 

[Mikey_P_HGT]

was just thinking the same thing, i been playing with it all morning, mechanic is coming down tuesday now(apparently), its all up 2 him now and to make matters worse i only got one blue key and no code card...things are going from bad to worse!!

 

[Mikey_P_HGT]

The car has just been picked up and taken to be fixed...will post the findings when its back and hopefully working for future reference

 

[Turracan]

Nice one! Going Newquay in mine tomorrow wish me luck! lol.

 

[Mikey_P_HGT]

haha all the best

 

[PUNTOELXBERTONE]

Air Flow Sensor??? My Old Escort Cut out many time due to this.

 

[The Sultan]

ok well the cutting out i was guna say crank sensor maybe not working so well under idle meaning cutting out if the revs drop and not starting

but as it has now stopped all together there may be an earth problem it's quite common for the earth on the ecu to fail it's bolted to the throttle body and can corrode meaning engine ecu has trouble

it's posable both these are true

the flat spot is probably a fault with the timing variator there is an electronic valve controlling them that are prone to failing the rpm's you say it happens are the kind of rpm's were this little baby should be giving you masive licks of power

temp sensor in the thermostat runs the engine ecu and gauge together as it's a modern car with can networking there for the temp that the gauge says is the correct temperature of the engine

 

[Mikey_P_HGT]

i had a quick word with him and he reckons the plugs are not giving a spark, so could this be the immobiliser kicking in overtime telling the engine not to ignite? or would the immobiliser not let the fuel pump prime? the plugs are in good condition. The affected rpm u reckon it could be the variator? are we talkin big expense or? thanks for your input btw...On the road 2 weeks and nearlly off for just as long, didnt realise fiats were such hassle

 

[The Sultan]

i had a quick word with him and he reckons the plugs are not giving a spark, so could this be the immobiliser kicking in overtime telling the engine not to ignite? or would the immobiliser not let the fuel pump prime? the plugs are in good condition. The affected rpm u reckon it could be the variator? are we talkin big expense or? thanks for your input btw...On the road 2 weeks and nearlly off for just as long, didnt realise fiats were such hassle

shame you seem to have a lemon but it probably wont take much to fix

the variator valve is quite cheap and easy to replace it's in plain view on top of the engine mounted in the inlet manifold fasing up with a plug connector on top of it

if the pump is priming then the ecu is working and immobiliser is off

as it's not sparking then that's gunny be crank sensor but always worth checking the live 12v feed to all the coils when ignition is on

it's mounted round the back of the block above the starter motor on them iirc at the fly wheel end there about 35 quid iirc so not to bad

 

[Mikey_P_HGT]

cheers for your help pip, when i know anything i will post it up