Technical Bad idle and sputtering only at idle after installing a new Magneti Marelli throttle body!!

[Alfa33boxer81]

Hi guys, I'm new in here a new seicento owner. I know this might have been already discussed before but I haven't found anything helpful regarding the issue I'm having. Someone can give me a tip on the problem I've been having lately with my Seicento SX (187) 1.1 mpi


I've had the car for a short while and as I had noticed, the throttle body had been manipulated, because the throttle stop screw had been touched, I thought about buying a new throttle body (Magneti Marelli) and installing it.
Once the work was finished, I noticed that the car has become very light under acceleration and pulling like crazy but has developed a problem with the idle. At the beginning the idle remained high and accelerated, but after 2 days now it barely holds the idle and mumbles... sputtering


I reset the control unit via Multiecuscan, I drove it in different ways to give the control unit time to learn the new values but instead of improving the situation it is getting worse .
When the fan starts up I noticed that the idle settles a little then when it switches off the story starts all over again.


This only happens when the car is already warm, and is less noticeable with a cold engine.


It seems as if the stepper motor is not keeping up right, but it is new... With the engine running if I unplug the stepper motor the idle is established but there are gaps when you press the accelerator.


How is this possible if the throttle body was put in new... I checked the two rubber hoses under the air filter and they are fine so I exclude leaks from the vacuum tubes. The car has no errors and the live data in Multiecuscan did not show anything suspicious. The map sensor was also cleaned previously last week with a a proper MAF cleaner.


Can you help me please?!
Thanks in advance


Elvis

 

[bugsymike]

Hi guys, I'm new in here a new seicento owner. I know this might have been already discussed before but I haven't found anything helpful regarding the issue I'm having. Someone can give me a tip on the problem I've been having lately with my Seicento SX (187) 1.1 mpi


I've had the car for a short while and as I had noticed, the throttle body had been manipulated, because the throttle stop screw had been touched, I thought about buying a new throttle body (Magneti Marelli) and installing it.
Once the work was finished, I noticed that the car has become very light under acceleration and pulling like crazy but has developed a problem with the idle. At the beginning the idle remained high and accelerated, but after 2 days now it barely holds the idle and mumbles... sputtering


I reset the control unit via Multiecuscan, I drove it in different ways to give the control unit time to learn the new values but instead of improving the situation it is getting worse .
When the fan starts up I noticed that the idle settles a little then when it switches off the story starts all over again.


This only happens when the car is already warm, and is less noticeable with a cold engine.


It seems as if the stepper motor is not keeping up right, but it is new... With the engine running if I unplug the stepper motor the idle is established but there are gaps when you press the accelerator.


How is this possible if the throttle body was put in new... I checked the two rubber hoses under the air filter and they are fine so I exclude leaks from the vacuum tubes. The car has no errors and the live data in Multiecuscan did not show anything suspicious. The map sensor was also cleaned previously last week with a a proper MAF cleaner.


Can you help me please?!
Thanks in advance


Elvis

I know you have checked the two rubber hoses but an air leak can give those symptoms and somtimes you can locate them with a length of rubber hose held to your ear whilst checking around the engine with the other end of hose.
Another trick is to use brake cleaner spray around inlet area, if there is a leak the engine revs will pick up as it burns the brake cleaner. Obviously do in a safe manner.
I assume nothing like a brake servo vacuum leak?

 

[Alfa33boxer81]

I know you have checked the two rubber hoses but an air leak can give those symptoms and somtimes you can locate them with a length of rubber hose held to your ear whilst checking around the engine with the other end of hose.
Another trick is to use brake cleaner spray around inlet area, if there is a leak the engine revs will pick up as it burns the brake cleaner. Obviously do in a safe manner.
I assume nothing like a brake servo vacuum leak?

I have already checked for air leaks multiple times trust me...but I can try the old brake cleaner trick to be 100 percent sure. I already re tightened the new THB with a bone cold engine.
A brake servo vacuum leak...we'll I don't know but at the moment I'm running without the ABS in function as I broke one sensor...but the car still brakes very very good. How can I check the brake servo for leaks any special way.

As I said I'm encountering problems only at idle, in gear the car runs like a dream under acceleration, constant load and also deceleration

It sounds a bit strange that the first 2 days after THB installation the car was idling constantly high and than by itself it settled the idle to low. Resetting the ECU or disconnecting the battery brings back the high idle for the next 100/150 km and then it settles down.


With the old throttle body it also had a low idle but wasn't sputtering and hunting like this

 

[Alfa33boxer81]

I did a test by putting my hand over the throttle and the engine turns off... so the theory of the leaking air falls. Either the new stepper motor is already defective or there is a way/some procedure (that I don't know) to make the new stepper motor learn/start. The car runs in gear like a dream. I tried a trick that I found on the forum. Unplug the stepper motor... turn the key to MAR for more than 10 seconds... turn the key off for more than 10 seconds... plug the stepper motor back in... turn the key back to MAR and turn the engine on... It seems to run a little more regularly now but I only kept it on for 5 minutes. Afterwards when I go out I'll see how it goes

But I can definitely confirm it is surely and only the stepper motor what is causing the whole problem. Well if the stepper motor itself is the culprit or something else tells it to behave like this I can't tell. Looking at the live data I can't notice any strange things out of normal apart the cycling of the stepper motor that moves to much around . I have the full version of the Multiecuscan which I use for my Giulietta Cloverleaf and it shows all of the parameters. Everything looks good and after trying this trick disconnecting the ICV the timing seams to be more stable and not jumping to much around at idle as was doing when the idle was hunting... I also downloaded the IAW Scan 2 but it doesn't support the seicento MPI

 

[Alfa33boxer81]

And then again I did reset the ECU for the 3d time and after that the Seicento keeping a relatively high idle for the first 200km and exactly after 200 km from resetting the ECU it's drops the idle rpm and sputtering almost like a slightly misfire. It doesn't stall it just idles like ****. I really suspect on a faulty stepper motor already fon factory in the new throttle body, because the car really runs very clean in every gear and pulls right . I'm gonna drive it like this for some one week to see if it eventually can cure itself up...if not the next move will be buying a new stepper motor from a good brand and install it to the new THB.

 

[Alfa33boxer81]

Hi guys, hope you are all doing well.

Even though the throttle body is new the Seicento still doesn't idle right when at operating temperature. I decided to change the idle control valve (stepper motor) as I thought it might be faulty from factory as the Magneti Marelli THB are now produced in China. So I put a new IAC valve and I also put a new intake manifold pressure sensor on the intake but still no success. The car still idles like crap. Any idea what can be the next move?

Regards
Elvis

 

[bugsymike]

Sorry only just seen your recent posts.
Re servo, easiest thing is to blank the vacuum pipe to servo , or any other suspect vacuum pipes to see if it makes a difference, often a small vacuum leak may just weaken mixture enough to cause a low speed problem, so a quick check to eliminate may be worth doing.
Especially as Fiats have a habit of rusting the brake servo drums on some models.

 

[Alfa33boxer81]

Sorry only just seen your recent posts.
Re servo, easiest thing is to blank the vacuum pipe to servo , or any other suspect vacuum pipes to see if it makes a difference, often a small vacuum leak may just weaken mixture enough to cause a low speed problem, so a quick check to eliminate may be worth doing.
Especially as Fiats have a habit of rusting the brake servo drums on some models.

The one going from the rockers cover to the air housing and intake manifold it's intact, I have triple checked it. The intake manifold itself it's also not letting any air as the engine cuts out if I put my hand on the throttle body.
The pipe going to the brake servo I have only checked visually and looks good, but as you suggested it's a good idea to blank it and see if something changes. If I try to sniff at the exhaust fumes I don't smell anything so it is burning the fuel efficiently...also no unburned fuel comes out from the exhaust which makes things more difficult sto locate the problem...this excludes any possible misfires (coil/sparks/cables)
I also added an earth connection from battery to ECU but nothing changes.

I have noticed sometimes the car starts with half crank turn and sometimes takes a bit longer like a 1-2 rotation but this might me normal. I run also a full tank with an injection cleaner from Ravenol just in case it coul help.


I think I'm at the point where I have to go randomly with the rest of the sensors and replace them (crankshaft sensor, camshafts sensor) and maybe battery, coils and check the sparkplugs...but then I get lost because the car runs perfect in any gear

If this car had a air flow meter sensor I would have bet on that sensor as this is a typical symptom, but this car has no air flow sensor after the air filter so it's deffo something else acting like that

 

[bugsymike]

Ideally you need to see a fault before replacing parts sensors etc.
Two things, one the breather from rocker cover to inlet manifold, is there any kind of valve , does blocking or bypassing change engine issue?
Two is there any way a temp sensor is affecting things?
Another small point, I am not sure if you mean this , but putting your hand over a throttle intake can cause seals gaskets to "suck in" and I was always told to avoid that. Apologies if that is not what you meant
Does your MES show live readings of Lambda? Is it possible to see if gradually increasing engine speed Lambda is going out of tolerance which may indicate a too weak or rich point causing the issue.
I know you have sniffed the exhaust , but it may only be a small discrepancy.

 

[Alfa33boxer81]

Ideally you need to see a fault before replacing parts sensors etc.
Two things, one the breather from rocker cover to inlet manifold, is there any kind of valve , does blocking or bypassing change engine issue?
Two is there any way a temp sensor is affecting things?
Another small point, I am not sure if you mean this , but putting your hand over a throttle intake can cause seals gaskets to "suck in" and I was always told to avoid that. Apologies if that is not what you meant
Does your MES show live readings of Lambda? Is it possible to see if gradually increasing engine speed Lambda is going out of tolerance which may indicate a too weak or rich point causing the issue.
I know you have sniffed the exhaust , but it may only be a small discrepancy.

So I tried to blow back from the rubber hose that goes in the filter housing and it is definitely letting air only through the smaller pipe that goes into the inlet manifold...only in that direction and not back to the rocker cover. Visually I don't see any valve in there but but I assume there should be some kind of one directional valve inside the rocker cover as it lets air flow only in one direction.


Temperature sensor is showing good values and during highway drive the temp stays around 88°C which I assume it's correct and the temperature sensor is working properly.


The trick with the hand on the throttle body intake I did just once to exclude a possible intake manifold leak, hopefully I have caused no extra problems.


When I monitor the lambda with MES It fluctuates and the values are not greater than 0.8/0.9 volt which is wright but it's reacting a bit slow.
I think is wise to pull the spark plugs out and check their colour and gap...or even if they are the right ones

 

[Alfa33boxer81]

Would a dodgy lambda not trigger a check engine light????

 

[bugsymike]

Would a dodgy lambda not trigger a check engine light????

Normally I would say yes, but if it is just a bit lazy, maybe not.
If the problem started directly after fitting the new throttle body, is there anything that may have been disturbed at that time?
I don't use MES, but voltage readings between weak at .1v and rich at .9v with yours .8-.9v max, but still in Lambda values.
I am not a great fan of chinese throttle bodies etc. and I know with carbs on older Fiats they can contribute to other problems, however sometimes it is all that is available
Were you able to compare the old and the new to see if anything different, re any adjustments or port sizes/drillings etc.
Re the carbs I know sometimes swarf and other things can be a problem re quality control as they sell incredibly cheaply, at least before they arrive in our Countries.
Perhaps someone else on Forum can shed more light on the problem?

 

[Alfa33boxer81]

Normally I would say yes, but if it is just a bit lazy, maybe not.
If the problem started directly after fitting the new throttle body, is there anything that may have been disturbed at that time?
I don't use MES, but voltage readings between weak at .1v and rich at .9v with yours .8-.9v max, but still in Lambda values.
I am not a great fan of chinese throttle bodies etc. and I know with carbs on older Fiats they can contribute to other problems, however sometimes it is all that is available
Were you able to compare the old and the new to see if anything different, re any adjustments or port sizes/drillings etc.
Re the carbs I know sometimes swarf and other things can be a problem re quality control as they sell incredibly cheaply, at least before they arrive in our Countries.
Perhaps someone else on Forum can shed more light on the problem?

The car was also idling poorly previously the throttle body change, that's why I decided to put a new one in. I'm not a big fan of Chinese parts either and I don't buy cheap parts or try to save a few bucks when it comes to spare parts. This new one I put is a Magneti Marelli and i didn't know they're now produced in China... anyway I did compare the two and they were identical fiscally, even the numbers stamped on the throttle body are the same. Just the idle control valve and TPS were no name in the new one. Anyway I did put a new idle control valve (stepper motor) made in Germany but still the same behaviour.


The lambda values fluctuate (go up and down) between 0.3v - 0.8/0.9v but the reaction is a bit slow when at idle, it stays at the minimal value for a certain amount of time and than jumps to the other extremity value... sometimes just jumps up to half way around 0.4/0.5 v and doesn't go all the way up to 0.9v...it looks more like a random movement and not like normally lambda does (high/low/high/low). Sometimes driving with MES connected it was randomly switching by itself from closed loop to open loop and again to closed loop (I don't think this is normal either)


I hope someone else can give an opinion on this problem I'm having. Initially I didn't care much about the Seicento as it was just a emergency car until my Giulietta Cloverleaf 235 hp has its engine rebuild...but in this 4 weeks of ownership I have started to love this little car and want to keep it long term, that's why would like to fix some issues it has and enjoy it.


One last thing, earlier with the ignition on I played with the gas pedal: pushing it slowly all the way down and releasing it slowly all the way up X 6 times and suddenly the motor engine light started to blink . Did I involuntary started some kind of procedure/ECU reset/ECU restart/TPS reset/some hidden feature which nobody knows about. I didn't try to start the car and turned the ignition off, but now I'm really tempted to try redoing the same procedure and find out what it can bring if you start the car right after the check engine blinks

Has anybody hear of something like this before... I can't find anything on the web. Will try to make a video and post it here.

 

[bugsymike]

The closed loop/open loop thing may be to do with throttle position sensor issues.
Another thing although I would expect to see an error code come up is with regards to Lambda reaction times if yours is a 4 pin lambda sensor two of the pins are for the heater element of the lambda sensor and the other two pins are the sensor readings.
By the way does your vehicle have a before and after Cat sensors or just the one.
You may also be able to read on MES the accelerator pedal positions on some vehicles.
No idea about six times pedal bit, although there are different commands activated on some makes by pressing pedals to trigger things like Diesel DPF Regens etc.

 

[Alfa33boxer81]

The closed loop/open loop thing may be to do with throttle position sensor issues.
Another thing although I would expect to see an error code come up is with regards to Lambda reaction times if yours is a 4 pin lambda sensor two of the pins are for the heater element of the lambda sensor and the other two pins are the sensor readings.
By the way does your vehicle have a before and after Cat sensors or just the one.
You may also be able to read on MES the accelerator pedal positions on some vehicles.
No idea about six times pedal bit, although there are different commands activated on some makes by pressing pedals to trigger things like Diesel DPF Regens etc.

Mine has a pre cat and an after cat lambda and yes the pre catalytic is a 4 pin I think...if so it has its own heating circuit, wich I'm not able to test unless I take the lambda out its placed...keep it in my hand and turn ignition on to se if it gets warm

As you say the open/closed loop position is connected somehow with the throttle position sensor because after a certain rpm range or full throttle accelerations the lambda will be ignored, but in my case this was when releasing the accelerator or with a tiny amount of pressure on it, so definitely in the range where it should be measuring and closed loop


Yes I can definitely see with MES the position/throttle opening and strange enough it shows max 84% and at idle 0.2%

The old throttle body used to show values up to 97% but anyway I don't see a problem here as the car runs ok in gear

 

[bugsymike]

I think on some vehicles the heater circuit if measured at the plug has 12 volts sometimes between the two white wires where as the signal side is 5volts in etc.
TPS % may be a bit out at .5% some say between 5 and 20% not .5% and I would like to see something nearer to 100% at full throttle.
Maybe someone with similar model to yours can confirm what theirs reads on MES?
All I have is diesels these days

 

[Alfa33boxer81]

I came across this interesting article which apparently describes the same identical problem but in a Punto 1.2 /8v engine and the solution someone found to this problem.

FIAT F.I.R.E. 1.2 8v (44kW) benzinmotor alapjárati problémáinak megszüntetése - Fiat Punto II - Puntonium Blog

Ez a leírás azért jött létre, mert a szinte típushibának mondható üresjárati fordulatszám ingadozásra érdemben sehol sem található megnyugtató műszaki javítási/karbantartási útmutató.

www.puntonium.hu

I don't know if if this will be the same solution for the 600 but it's very interesting what this Greek guy has come to.




Where is this panel and this red main relay located in the seicento, maybe worth a try putting there a new ignition relay

 

[Alfa33boxer81]

I came across this other very interesting post in the forum. Is has some interesting info and a potentially solution to everyone who has a unstable idle or occasional engine stalling:

MPI 1.1 1.2 unruhigen Leerlauf und Motorruckeln beseitigen - Cento.World - Das neue Forum für Cinquecento und Seicento

Hallo Leute, zum Thema schlechter Leerlauf und/oder Motorruckeln gibt es was neues. Diese Anleitung ist für alle Modelle in denen der 1.1 und 1.2 Motor verbaut ist: Seicento - Doblo - Panda - Punto - Palio , dabei spielt das verbaute Motorsteuergerät…

cento.world

The post is in German league but hopefully you can translate it...


I have already played with my cables and I think I have found this joint the article talks about, but I haven't opened it yet as I'm going to try and change first a few things like lambda sensor, spark plugs, ignition leads, coils and crank sensor. If none of this parts does the trick then I'll try to attack the joint on the cables harness and solder it.

I also suspect that (as in the first article explained) one of the 2 relays (red) in the engine bay just beside the ECU, even though stil in working order it may have developed some "parasite" resistance and after 23 years after their production I think it's wise to put new once. For now I just switched the place of the 2 red relays to see if this brings any benefit... Will tell after 50-100 km

 

[Alfa33boxer81]

Today came the new NGK oxygen sensor I ordered. As I was under shock from the news I got about my Giulietta QV, which apart it's engine has also broken it turbo...I had the box in my hand and the oxygen sensor fell out its box and then on the floor in my apartment. Now I'm very concerned if something has happened to the sensor, if it still ok or if it won't work correctly once installed... Oh man, why did this happened, I feel so frustrated right now, because every time thing start to go in the right direction it's always going to happen something. I hope the O2 sensors are robust enough to handle a dropping like this.

I'm still waiting for the spark plugs, leads, coils and crank sensor to arrive and than I'll have to tackle. Hopefully one of this parts will be the culprit of the bad idle. If not remains only the temperature sensor and then I'm out of ideas.


Cheers
Elvis

 

[bugsymike]

Fingers crossed Oxygen Sensor should survive