Hi folks,

Ive an 2002 fiat stilo 1.6.... i have a problem with the car which is now becoming very frustrating!

It started with the engine light coming on whilst holding/maintaining revs over 3000rpm for say 20 seconds... then this happened more often on normal drives and lower down the rev range and also not requiring the 20 seconds but more like 4 seconds.
Then on idle the car started to hunt and stall.
The car then really started to become a pain...on pulling away the car around 1250rpm would hesitate and bog down..so the clutch had to be dipped and rode to keep the revs up...after the intial bogging down the revs would suddenly shoot up and it would drive normal. At this point on idle it would hunt...nearly stall, pick up again...repeating itself until it stalled completely.
Had the rac out....diagnostics said throttle body, track one. So bought a working 2nd hand throttle body and did the throttle learn...no change.
So i bought a working ecu (along with body computer and key as my central locking had stopped working a week before)... fitted all ok...but same happened.
Took it to a guy i know who has diagnostic equipment... we cleared the ecu of all fault codes....did the throttle learn...cleaned the fusebox next to the battery..checked each coil...spark plug and did a compresssion check... no problems...no fault codes.

Took it for a drive to see what fault codes would come up... none come up.

Once i had driven the car hard...the idle was fine and it pulled away better but was still bogging down at 1250rpm. Also if the revs were maintained at 3000rpm i could feel the car hesitating then clearing.
Other notes...went round a roundabout...problem of hesistation occured.

After getting back and engine turned off for 6/7min... on start up.. idle hunting and stalling bad again...and on pulling away very boggy..again! Engine temp was near enough half way and hadnt cooled much since the drive.

Put on diagnostics...no fault codes.
So...we are thinking fuel related..fuel pump??

Anyone have any clue? Thanks.

Maybe check spark plugs ( gap )

..gap was checked on the plugs.... thanks though.

Sounds like bad IAC valve ( Idle Air Control).
On earlier models, this is a separate valve ( inexpensive on Ebay), later versions have it inside the throttle body.
Clean it, and the passage where it moves, with carburetor cleaner first.

My stilo has the magneti marelli c146 throttle body...does this have the IAC valve integrated in it?
Ive replaced the throttle body with a working second hand one...plus i cleaned it...i put my old one back on...exactly the same...did the throttle learn process via the diagnostic software. Thanks.

try a new crank sensor (it is cheap and could, theoretically, be the cause of your woes :tempt although the reading on the throttle body is interesting (but has not returned? if it has - there is another recent post for a 1.6 experiencing throttle body issues - have a look at it and, specifically, the link to an older post that you will find within)

Cheers...

Yeah very strange that the fault code for the throttle body has gone.

I guess ive nothing to loose by putting a new crankshaft sensor on...though ive no problems starting to the car...cold or hot.

The car revs normal when out of gear and not under load.
Ive not had a cam belt change either recently...(2 years ago).

We thought it couod be a coil as it only happens under load.... one coil is an aftermarket and its values on the diagnostics were fluctuating ever so slightly compared to the constant values of the other three oem coils...possible?

Im trying to understand also as to why after it had been driven...and driven hard..the idle was ok and the boggyness had decreased?

Im at that point that if i cant resolve the issue within the next week and for less than £100..i will be selling as spares or repairs.

coils.. some new info.. may well be as they work in pairs and 2 that are not matching tend to cause a problem.. try a new oem coil first shop4parts usually have some

...well it looks like its the pre-cat lambda.
After reading that the lambda can be faulty yet not bring up any fault codes...i disconnected the lambda and it ran much better. Connected the lambda again and within 2 min the engine hunted and as it was about to stall i disconnected the lambda again..the engine idled fine straight away. There is no hesitation etc when driving now.
Im hoping it is just the lambda and not something else causing the lambda do play up?!

Thanks.