Technical Hesitation when pulling away, 500 Lounge, 2018 with 1.2 engine, no fault codes

[500baz]

This is my first post since joining the group.

I bought my 2018 Fiat 500 Lounge two months ago. There are a few things to sort on it but generally I'm pleased with it.
I've done a fairly full service including plugs.

It's a manual gearbox. When pulling away from stationery, while simultaneously engaging the clutch and applying pressure to the accelerator pedal the car initially pulls, then very briefly hesitates. It hesitates for only a couple of seconds then picks up again. I have a basic OBD setup on a laptop and no fault codes are showing.

I've searched the internet including here (fiatforum.com). Based on what I've seen it would appear if there are issues with the electronic components at the pedal or at the throttle body then fault codes would likely be displayed.

My feeling is if there are no codes then the pedal and throttle electronics need synchronising. Does that make sense? Many thanks in advance.

In order to carry out this synchronising it would require a more sophisticated OBD software set up, i.e. the MultiECUscan. For this I would need to pay for a software licence, a suitable laptop and a cable to join the laptop to the OBD socket.

 

[Greasytrucker]

Could just be a dirty throttle body that needs a clean.

 

[John202020]

Two simple things you could try
Have someone else try driving the car see what they say?
Run it low on fuel and then fill with E5 super unleaded for two tank fulls

 

[ZaphodB]

Has it got stop/start ?

Do the symptoms persist with it disabled?

 

[The Panda Nut]

Clean the throttle body and the VVT variator. The variator sits on top of the engine and is a small cylinder held in place with one set screw. Unclip the elctrical connector and lever the variator out gently. Clean with carb cleaner very thoroughly. Squirt it up imside the end untill it runs out clean. Dunk cleaned variator in clean engine oil for a minute and replace. Also clean the MAP sensor with a little carb cleaner and allow to dry. In combination these actions will make a difference. Dirty throttle body can make a big and bad difference to the idle and running particularly at low speed.

 

[puntodeltathema]

Have you read the threads on the infamous Euro 6 (2014 on) throttle map? On these cars, pickup from rest can be a little hesitant/jumpy until one gets used to it. If you let the clutch pedal up slowly while idling you should hear the revs pick up slightly (it sort of does the "bite point" for you) and it is possible to get the car moving without touching the throttle (at least on the flat). When I owned a 2017 car I found that "relearning" my take up reflex from the traditional bite point to the point at which the car transitions from first moving to moving more purposefully helped smooth out moving off.

 

[ZaphodB]

Have you read the threads on the infamous Euro 6 (2014 on) throttle map? On these cars, pickup from rest can be a little hesitant/jumpy until one gets used to it. If you let the clutch pedal up slowly while idling you should hear the revs pick up slightly (it sort of does the "bite point" for you) and it is possible to get the car moving without touching the throttle (at least on the flat). When I owned a 2017 car I found that "relearning" my take up reflex from the traditional bite point to the point at which the car transitions from first moving to moving more purposefully helped smooth out moving off.

Ahh yeah, is that the same thing that does it when in reverse as you slowly bring the clutch up, the revs start to 'pulse' gently.

Both took me a month or so after I bought my 595 for my foot and brain to (re)learn the behaviour.

 

[500baz]

Could just be a dirty throttle body that needs a clean.

Thanks, and yes good point. I changed the air filter on service. With the air box removed I saw gunge on the butterfly valve. I cleaned it from the outside. I was reluctant to remove the throttle body for cleaning. It might need re-synchronising with special OBD which I don't have currently.

 

[500baz]

Two simple things you could try
Have someone else try driving the car see what they say?
Run it low on fuel and then fill with E5 super unleaded for two tank fulls

Thanks John, will try these.

 

[500baz]

Has it got stop/start ?

Do the symptoms persist with it disabled?

Yes it's got s/s. I usually switch off, though I'm fortunate I don't regularly drive through lots of built up traffic.
But it happens both on/off.

 

[ZaphodB]

Yes it's got s/s. I usually switch off, though I'm fortunate I don't regularly drive through lots of built up traffic.
But it happens both on/off.

I was kinda thinking if the various switches on brake and clutch that SS relies on were misbehaving that might provide your symptoms, but if it's the same with it off and on then please ignore.

 

[500baz]

Clean the throttle body and the VVT variator. The variator sits on top of the engine and is a small cylinder held in place with one set screw. Unclip the elctrical connector and lever the variator out gently. Clean with carb cleaner very thoroughly. Squirt it up imside the end untill it runs out clean. Dunk cleaned variator in clean engine oil for a minute and replace. Also clean the MAP sensor with a little carb cleaner and allow to dry. In combination these actions will make a difference. Dirty throttle body can make a big and bad difference to the idle and running particularly at low speed.

Thanks Panda, I really appreciate your detailed response together with detailed instructions on how to complete the points mentioned.

 

[500baz]

Have you read the threads on the infamous Euro 6 (2014 on) throttle map? On these cars, pickup from rest can be a little hesitant/jumpy until one gets used to it. If you let the clutch pedal up slowly while idling you should hear the revs pick up slightly (it sort of does the "bite point" for you) and it is possible to get the car moving without touching the throttle (at least on the flat). When I owned a 2017 car I found that "relearning" my take up reflex from the traditional bite point to the point at which the car transitions from first moving to moving more purposefully helped smooth out moving off.

Thanks puntod, yes I think I understand where you're coming from. Releasing the clutch pedal and without any pressure on the throttle pedal the engine speeds up a bit enabling the car to move off. Then when it's moving you begin to press the throttle pedal. This works best when in particular when the engines still cold and tickover is a bit quicker.
I'll experiment a bit next time driving.

 

[500baz]

Many thanks to everyone for your time, opinions and expertise. I have some good points to follow up on. I will report with feedback. Kind regards.

 

[AnthonyH]

Possibly just one of the quirks of the car. The pickup of my EVO isn't uniform, i've gotten used to it.

Possibly a faulty component but tracking that down is going to be difficult.

Let us know how you get on.

 

[500baz]

Have you read the threads on the infamous Euro 6 (2014 on) throttle map? On these cars, pickup from rest can be a little hesitant/jumpy until one gets used to it. If you let the clutch pedal up slowly while idling you should hear the revs pick up slightly (it sort of does the "bite point" for you) and it is possible to get the car moving without touching the throttle (at least on the flat). When I owned a 2017 car I found that "relearning" my take up reflex from the traditional bite point to the point at which the car transitions from first moving to moving more purposefully helped smooth out moving off.

Well referenced puntodel, I've read some of the posts/replies, I found this one ....

"Euro6 1.2 Throttle Response, Hill Start Issues & Watchdog report"

I think this thread is connected with what I'm describing, its a very long thread! The first post was entered December 2013 and the last one was on March 2024!

Many thanks.

 

[500baz]

Following all the response posts from a few days ago, I've been experimenting paying particular attention to pulling away from stationary.

The car will pull away from stationary by engaging the clutch and without applying any pressure to the accelerator pedal.
It does this quite comfortably albeit it does not accelerate quickly, it would be fine pulling away on a quiet road but not say pulling out of a busy junction with a lot of traffic.
Of course after pulling away like this after a few seconds one has to depress the accelerator to come up to speed which is when the brief hesitation occurs.
I then asked myself the question would this work when pulling away from stationary on hill? And yes it did on a moderately steep hill.

I further tried it on quite a steep hill, I couldn't quote the percentage incline, suffice to say it was of such steepness that required the handbrake to be pulled up more forcefully than usual to hold the car on the hill. So, with the car in first gear, and no pressure at all on the accelerator, the engine is on tickover, I engage the clutch slowly and the car pulls away. I was surprised! Therefore I assume the ecu is opening the throttle and increasing the amount of petrol and air into the engine and hence the engine has the required power to pull away on the hill, but without increasing the engine RPM, it remains more or less on tickover.

I'm surprised by all this, being "old school" I thought all cars had accelerator cables to actuate the throttle within the carb or throttle body! That was until buying the Fiat and looking into all this did I realise the throttle is advanced by some sort of potentiometer on the pedal and presumably a solenoid moving the throttle butterfly.

I removed the VVT solenoid, cleaned it with carb spray cleaner, oiled it with engine oil and replaced it - I thought this might bring a result because when I bought the car in April I believed the oil had not been changed for some time, the oil was quite dirty another give away the oil filter had rust on the outside! I've never seen rust on the outside on a car's oil filter before. So driving it after cleaning - no noticeable difference!

I then cleaned the MAP sensor and driving it after there seemed no noticeable difference!

I'll try a further clean of the throttle body on the next session.

It won't be a big deal if this hesitation isn't resolved. And I'm half expecting it won't be! Though I'm finding out new automotive stuff!

 

[AnthonyH]

Following all the response posts from a few days ago, I've been experimenting paying particular attention to pulling away from stationary.

The car will pull away from stationary by engaging the clutch and without applying any pressure to the accelerator pedal.
It does this quite comfortably albeit it does not accelerate quickly, it would be fine pulling away on a quiet road but not say pulling out of a busy junction with a lot of traffic.
Of course after pulling away like this after a few seconds one has to depress the accelerator to come up to speed which is when the brief hesitation occurs.
I then asked myself the question would this work when pulling away from stationary on hill? And yes it did on a moderately steep hill.

I further tried it on quite a steep hill, I couldn't quote the percentage incline, suffice to say it was of such steepness that required the handbrake to be pulled up more forcefully than usual to hold the car on the hill. So, with the car in first gear, and no pressure at all on the accelerator, the engine is on tickover, I engage the clutch slowly and the car pulls away. I was surprised! Therefore I assume the ecu is opening the throttle and increasing the amount of petrol and air into the engine and hence the engine has the required power to pull away on the hill, but without increasing the engine RPM, it remains more or less on tickover.

I'm surprised by all this, being "old school" I thought all cars had accelerator cables to actuate the throttle within the carb or throttle body! That was until buying the Fiat and looking into all this did I realise the throttle is advanced by some sort of potentiometer on the pedal and presumably a solenoid moving the throttle butterfly.

I removed the VVT solenoid, cleaned it with carb spray cleaner, oiled it with engine oil and replaced it - I thought this might bring a result because when I bought the car in April I believed the oil had not been changed for some time, the oil was quite dirty another give away the oil filter had rust on the outside! I've never seen rust on the outside on a car's oil filter before. So driving it after cleaning - no noticeable difference!

I then cleaned the MAP sensor and driving it after there seemed no noticeable difference!

I'll try a further clean of the throttle body on the next session.

It won't be a big deal if this hesitation isn't resolved. And I'm half expecting it won't be! Though I'm finding out new automotive stuff!

I find it engaging to learn new things. So i've spent a while chasing my tail and getting nowhere!

Its possible you'll get there, but like you say no need to sweat it.

 

[The Panda Nut]

Three things on top of service. Thottle body, MAP sensor and gunge inthe manifold, vvtvariatot. Combined these should resolve this. VVT THING SREMS TOBEGENTLE DRIVING. once free and working these vvt engines really deliver. They need regular spelss opened upand thevariator will properlyfree up. Transformative.