I had the same problem, and no matter which diagnostic tool Alfanige used on it the error would not appear nor could he remedy it, he then went to another Stilo with the same problem and after some experimentation and communication with his Italian and German counterparts, they came up with this fix, he phoned me up, I went out and did it and hey presto instant fix, smooth acceleration, no beep beep or fault light.
Technical Battery Change now Engine Fault? No Revs?
- Thread starter Nello
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Technical Battery Change now Engine Fault? No Revs?
Oh, let me know if it works.
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Nello
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So this'll fix my idle issue? Acceleration etc is fine just the idle?
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Nello
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OK tried last night on the way home from work without success?!! 
Though I did it after I had driven home rather than allow to warm from Cold? Would that make a difference?
The initial errors that I had when the Engine Fault displayed were:
P0638 - Not listed on the Diagnostics site??
P0120 - Throttle Position Sensor/Switch A Circuit Malfunction
So now I have no Engine Faults on the dash or display - The car drives perfectly apart from its Idle? Cuts out every other time when I come to a halt? HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Though I did it after I had driven home rather than allow to warm from Cold? Would that make a difference?
The initial errors that I had when the Engine Fault displayed were:
P0638 - Not listed on the Diagnostics site??
P0120 - Throttle Position Sensor/Switch A Circuit Malfunction
So now I have no Engine Faults on the dash or display - The car drives perfectly apart from its Idle? Cuts out every other time when I come to a halt? HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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P0638 throttle actuator out of range
Have a look here
https://www.fiatforum.com/stilo/82903-p0638-throttle-actuator-control-range.html
P0120 - Throttle Position Sensor/Switch A Circuit Malfunction
and here
http://www.mojeepin.com/p0120.html
It's throttle actuator comms problems
Are these fault codes appearing now or some time ago?
Have a look here
https://www.fiatforum.com/stilo/82903-p0638-throttle-actuator-control-range.html
P0120 - Throttle Position Sensor/Switch A Circuit Malfunction
and here
http://www.mojeepin.com/p0120.html
It's throttle actuator comms problems
Are these fault codes appearing now or some time ago?
For what its worth, when Angel Tuning did my re-map it took about eight times of flooring the throttle til the rev limiter kicked in before it re-set itself...
of flooring the throttle til the rev limiter kicked in before it re-set itself...
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Nello
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The errors were cleared by the dealer so not showing but were showing when scanned after issue arose?
Interesting this, but I reckon you should give it another go, it definitely works!
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Nello
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OK Update - Got the car back today - A further Dealer Full reset including prior total ECU disconnection seemed to have initially worked - Throttle control seemed to respond OK? But having tried again today from cold theres still 50/50 Russian Roulette whenever you come to a halt if its gonna stall or not?!! Extremely frustrating. No error codes / display errors etc. All sensors (Lambda/Air Flow etc.) reading OK? They reckon theres a diagnostic plug on the throttle control to test if its reading from the ECU OK but cannot get the software at the mo............I've taken the car as is - Otherwise it drives perfectly but with the stalling the wife won't now drive it. Will clock some mile to see if it improves via re-teach but really do not want to spend £350 plus on a new throttle control assembly or even more on a new ECU if its deemed spike damaged by the original failing battery? ............to be honest - I'm at a loss...........This is the first and only issue I have had in 2 years of perfect trouble free Stilo ownership
They can leave the Examiner plugged in and check the parameters actively whilst it's playing up. What dealer are you using Nello?
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Nello
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It was at Carstins in Balsall Common rrope.........I used to use them years ago - they were a Fiat dealer for about 30 years until a few years ago when the UK dealerships were all re-organised and they took a dislike to any not city-centre based - even though they were one of the regions highest-selling franchises........Now they are Subaru but recently got official Fiat Authorised Repairers status back and you can still buy a new model through them. They are listed on fiat.co.uk
I bought a couple of X1/9's from them years ago and some of the Service guys are still there from the old days so I do trust them.....Just read about the D4 connector and its use for throttle potentiometer signal? Worth a try?
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Yeah, I'm not knocking the dealer, but if it were me, I'd take it to another one just to get a 2nd opinion - thats how I got my variator replaced (£500) under warranty with a few months left on it!
Yeah could be worth a go - seeing as it's happened since battery replacement, if it were knocked, it coulds be kicking up. Do you know which connector D4 is?
Have you cleaned the idle valve yet Nello? You don't say whether you have. If everything else is going fine and it just won't idle then clean that off first as per my guide in the Stilo guide section
The gas pedal position tells the ECU to "idle" and then the ECU takes over and alters the Throttle valve over very small incremements to maintain idle rpm. If the valve is sticking (which it does when it's coked up) then it all goes to pot. The throttle body has a valve position sensor which feeds back to ECU where the valve is so the ECU knows what's going on. Any interruption in comms between them or a sticking idle valve will make you lose your idle
If you have EOBD diagnostics connectors you can see gas pedal inputs v throttle valve position. Don't know whether you have that though
Is it idling perfectly ok and rock steady ok sometimes?
When it doesn't idle does it struggle, try, have lower than 500rpm then die?
The gas pedal position tells the ECU to "idle" and then the ECU takes over and alters the Throttle valve over very small incremements to maintain idle rpm. If the valve is sticking (which it does when it's coked up) then it all goes to pot. The throttle body has a valve position sensor which feeds back to ECU where the valve is so the ECU knows what's going on. Any interruption in comms between them or a sticking idle valve will make you lose your idle
If you have EOBD diagnostics connectors you can see gas pedal inputs v throttle valve position. Don't know whether you have that though
Is it idling perfectly ok and rock steady ok sometimes?
When it doesn't idle does it struggle, try, have lower than 500rpm then die?
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Nello
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rrope - OK will try to get a second opinion - I rate Motor-Mech in Brum who looks after my Alfa. Last time he serviced the Stilo he said he was getting the software in for the Stilos to be able to reset the Service Indicator etc. so might be able to crack?
I've printed off the D4 connector thread of here so should be able to trace OK? The one thing Carstins did say in relation to the 1.8 was the ECU was Hitachi rather than Marelli in the smaller engined cars which is a scarcer and was why he did not have all the proper diagnostics - he wanted to check the throttle valve position sensor but did not have the necessary tools?
Deckchair - cheers for the info - Not tried to clean the idle valve yet - working nights but finish Monday so will will try first thing then.....no time especially with a new baby in the house! The car was running perfectly before this all started though so I'd be suprised if its fouled up?
I've not got any EODB diags etc - or the skills?!
The idle is irratic - never like it was before - every time you come to a halt its 50/50 if its gonna stall or not? The revs drop right down to just a couple of hundred or so before either recovering to a shaky less than before 600 rpm or so or completely dying.......Its a lottery really but I've lost confidence in it not now happening so am finding myself left foot braking to keep my right foot on the throttle round town in-case it dies?.....
Aside from that the car drives perfectly on the move - no hesitation from pull off etc. Perfect through the gears etc. - Absolutely no issues aside from the reluctance to idle?!!!
I've printed off the D4 connector thread of here so should be able to trace OK? The one thing Carstins did say in relation to the 1.8 was the ECU was Hitachi rather than Marelli in the smaller engined cars which is a scarcer and was why he did not have all the proper diagnostics - he wanted to check the throttle valve position sensor but did not have the necessary tools?
Deckchair - cheers for the info - Not tried to clean the idle valve yet - working nights but finish Monday so will will try first thing then.....no time especially with a new baby in the house! The car was running perfectly before this all started though so I'd be suprised if its fouled up?
I've not got any EODB diags etc - or the skills?!
The idle is irratic - never like it was before - every time you come to a halt its 50/50 if its gonna stall or not? The revs drop right down to just a couple of hundred or so before either recovering to a shaky less than before 600 rpm or so or completely dying.......Its a lottery really but I've lost confidence in it not now happening so am finding myself left foot braking to keep my right foot on the throttle round town in-case it dies?.....
Aside from that the car drives perfectly on the move - no hesitation from pull off etc. Perfect through the gears etc. - Absolutely no issues aside from the reluctance to idle?!!!
ChrisF
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Nello,
I've had a VERY similar problem to you which only started after a battery change.
Used to cut out coming to a stop at busy junctions, low rev crawling at busy junctions and pulling away quickly.
If your car doesn't have air con fitted get them to check the aircon circuit for damage, corrosion and shorting. The aircon circuit is "kinda left dangling" if aircon isnt fitted, it lives on the the same circuit as the throttle control and when it shorts it throws the fault codes your talking about.
I've had the throttle body, ignition switch, spark plugs and ecu replaced but the DET managed to susccessfully replicate the fault every time when shorting out the air con circuit. Fortunatley all covered under warranty.
Now its all sorted, runs silky smooth and responds much quicker when you give it the boot...snarly tooo.
Give it a shot.
Chris
I've had a VERY similar problem to you which only started after a battery change.
Used to cut out coming to a stop at busy junctions, low rev crawling at busy junctions and pulling away quickly.
If your car doesn't have air con fitted get them to check the aircon circuit for damage, corrosion and shorting. The aircon circuit is "kinda left dangling" if aircon isnt fitted, it lives on the the same circuit as the throttle control and when it shorts it throws the fault codes your talking about.
I've had the throttle body, ignition switch, spark plugs and ecu replaced but the DET managed to susccessfully replicate the fault every time when shorting out the air con circuit. Fortunatley all covered under warranty.
Now its all sorted, runs silky smooth and responds much quicker when you give it the boot...snarly tooo.
Give it a shot.
Chris
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Nello
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Hi ChrisF - cheers for the insight but my cars a Dynamic with Air-Con?
Sorry to be a complete Chimp but whats 'DET'?
I take it just replacing the throttle body, ignition switch, spark plugs and ecu did not cure?
Any idea if the Air-Con circuit runs through the D4 connector? Am reading on the forum that that causes mystery faults and can easily be disturbed as its located just behaind the battery housing?
Sorry to be a complete Chimp but whats 'DET'?
I take it just replacing the throttle body, ignition switch, spark plugs and ecu did not cure?
Any idea if the Air-Con circuit runs through the D4 connector? Am reading on the forum that that causes mystery faults and can easily be disturbed as its located just behaind the battery housing?
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Would this procedure be relevant when fitting a sports airfilter. Is any sort of adjustment or ECU reset required to allow for the extra air being sucked in or does the ECU just adjust itself?
cheers
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Nello
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With looking at a fix in mind can anyone direct me to whereabouts the ECU and Throttle Body are on the 1.8 Stilo - prior to removal to test?
ChrisF
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Might be worth getting the aircon circuit checked, it was the switch that was faulty on my car. Sounds almost identical to the fault i had.
Throttlebody didn't sort it, ignition switch didnt sort it, spark plugs and ecu done at the same time as the aircon wiring but the aircon wiring allowed multiple replications of the fault...def worth getting checked.
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Nello
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Guys Update - SOLVED!!!!
Thanks to everyone and showing the power of this Forum to solve an issue even a Fiat dealer struggled with (I will be telling them!)
Most Gratitude to Deckchair5 - The Idle Control Valve was the cause - followed the guide on the forum and result! Superpleased! Actually the valve did not seem that dirty but cleaned and WD40'ed - The 1.8 was slightly different as it includes an in-line cir-clip and mesh to prevent anything entering the throttle-body but I feel that actually actuating the Butterfly Valve a few times through its full movement resolved. I think the ECU after having lost its config did not know where the valve was but moving through its full range has restored! Now really smooth and idles perfectly around 800 rpm! Thanks again all....
Thanks to everyone and showing the power of this Forum to solve an issue even a Fiat dealer struggled with (I will be telling them!)
Most Gratitude to Deckchair5 - The Idle Control Valve was the cause - followed the guide on the forum and result! Superpleased! Actually the valve did not seem that dirty but cleaned and WD40'ed - The 1.8 was slightly different as it includes an in-line cir-clip and mesh to prevent anything entering the throttle-body but I feel that actually actuating the Butterfly Valve a few times through its full movement resolved. I think the ECU after having lost its config did not know where the valve was but moving through its full range has restored! Now really smooth and idles perfectly around 800 rpm! Thanks again all....
