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.