General Leaping/surging behaviour when pulling away

[lycopersicum]

Hello all!
When I get going by slowly lifting the clutch pedal in 1st gear, there's a 1-second hesitation at the bite point before the rpms surge and the van sort of leaps forward before settling at a lower speed and lower rpms. It feels as if I'm giving it extra gas to get going, except I'm not moving my foot on the gas pedal. No big deal, but it requires some footwork to smoothe this out in stop-and-go traffic and not rear end the car in front. I'm just curious if yours does the same and if there's a technical reason for it. I've not driven many other types of vehicles so no idea if this is common.

 

[AnthonyH]

This sounds normal to me.

If you were to drive an automatic it'd smooth things out for you.

 

[lycopersicum]

All right, good to know that's normal behaviour.

 

[DenS]

Hello all!
When I get going by slowly lifting the clutch pedal in 1st gear, there's a 1-second hesitation at the bite point before the rpms surge and the van sort of leaps forward before settling at a lower speed and lower rpms. It feels as if I'm giving it extra gas to get going, except I'm not moving my foot on the gas pedal. No big deal, but it requires some footwork to smoothe this out in stop-and-go traffic and not rear end the car in front. I'm just curious if yours does the same and if there's a technical reason for it. I've not driven many other types of vehicles so no idea if this is common.

Being new to Fiat light commercials (I used to drive a 380BHP Fiat 190.38 truck ..and that was a flying machine! ) I bought a 2008 motorhome on a Ducato 2.3 chassis recently and have trawled through pages of posts and so glad to have found your post, for mine has exactly the very same problem...unless you sold yours and I ended up buying it! ....Have you found the cause, have you had it fixed or whatever?? other than this same problem it otherwise runs perfectly well and no errors codes whatever so... how is it now?

 

[lycopersicum]

It's the same and I don't think too much about it any more.

Seems to happen mostly when causing the revs to dip below idle. As if the ECU is reacting to avoid a stall, but with a lag.

So if I want to start and maintain a crawl speed, I pause at the bite point until the van's built up some momentum, or even give it a tiny blip of gas to maintain idle rpms.

In situations where it's unavoidable eg stop-and-go traffic uphill I've learned to anticipate it.

Being new to Fiat light commercials (I used to drive a 380BHP Fiat 190.38 truck ..and that was a flying machine! ) I bought a 2008 motorhome on a Ducato 2.3 chassis recently and have trawled through pages of posts and so glad to have found your post, for mine has exactly the very same problem...unless you sold yours and I ended up buying it! ....Have you found the cause, have you had it fixed or whatever?? other than this same problem it otherwise runs perfectly well and no errors codes whatever so... how is it now?

 

[DenS]

It's the same and I don't think too much about it any more.

Seems to happen mostly when causing the revs to dip below idle. As if the ECU is reacting to avoid a stall, but with a lag.

So if I want to start and maintain a crawl speed, I pause at the bite point until the van's built up some momentum, or even give it a tiny blip of gas to maintain idle rpms.

In situations where it's unavoidable eg stop-and-go traffic uphill I've learned to anticipate it.

Well thanks for the answer, I too quickly adapted to it's idiosyncrasy, but this cant be normal throtttle behaviour otherwise many many others would have reported it, but if you are happy then I am, I will not let it worry me

 

[AsdaPricey]

Could this be a by product of dual mass flywheels?
The wife’s now sold Mini Paceman behaved in a similar manner after having a new LuK clutch fitted

 

[Greasytrucker]

Doesn’t sound normal to me, as you said you can adapt your driving style but you shouldn’t have too. Have you tried cleaning your throttle body as this can cause those symptoms

 

[DenS]

Doesn’t sound normal to me, as you said you can adapt your driving style but you shouldn’t have too. Have you tried cleaning your throttle body as this can cause those symptoms

That will be on the cards, or replacing the whole thing eventually...but the first job to do is the windscreen water scuttle

 

[The Panda Nut]

All right, good to know that's normal behaviour.

Yes there will be an anti stall device and the revs are maintained at idle speed. Its sometimes noticable when running in traffic. Because of the torque of a diesel it can fel a little alarming as the car seems to take off by its self with no feet on the pedals. If you are new to diesel driving it takes a while to adjust. Sometimes using a diesel fuel additive can help to ensure the system is clean and runnng its best nothing much to be lsot from trying this for a couple of tanks of fuel.

 

[lycopersicum]

Yes I am satisfied by the explanation of an over-eager anti-stall. As you say it can be alarming because it feels the van wants to go faster than its eventual tickover crawl speed. But this could be a trick of the senses due to the surprising acceleration. I'll try to record it one day

 

[DenS]

Yes there will be an anti stall device and the revs are maintained at idle speed. Its sometimes noticable when running in traffic. Because of the torque of a diesel it can fel a little alarming as the car seems to take off by its self with no feet on the pedals. If you are new to diesel driving it takes a while to adjust. Sometimes using a diesel fuel additive can help to ensure the system is clean and runnng its best nothing much to be lsot from trying this for a couple of tanks of fuel.

I have been around diesels for all of my 50 years of driving commercial vehicles, and to be honest have never come across this on any diesel engined vehicle I have driven and operated, and that ranges from light commercials through to 44 ton articulated lorries. But... I have not driven Fiat Ducatos until now, is this really normal for any Fiat Ducato, either a Motorhome or a commercial vehicle? with that clarification answered, then I shall stop thinking of it as a potential problem and just enjoy the vehicle for what it is

 

[lycopersicum]

Just recorded the behaviour. No gas pedal application at all, just a fairly aggressive clutch start. Surges to 7 km/h initially then 5 on tickover. @DenS does this match what you see?

X axis is funky, 5 seconds per tick.

Mine often has a little hiccup just as I'm about to shift up to 2nd, I suspect it's the same assist mechanism turning off as speed builds up.

 

[DenS]

Just recorded the behaviour. No gas pedal application at all, just a fairly aggressive clutch start. Surges to 7 km/h initially then 5 on tickover. @DenS does this match what you see?

X axis is funky, 5 seconds per tick.

Mine often has a little hiccup just as I'm about to shift up to 2nd, I suspect it's the same assist mechanism turning off as speed builds up.

I'm sorry licopersicum, but have not got any programs or tech to run any sort of diagnostics, my judgements and opinion are from just pure feel of how it manifests itself, but I do understand to a point your attached graph.

 

[lycopersicum]

I'm sorry licopersicum, but have not got any programs or tech to run any sort of diagnostics, my judgements and opinion are from just pure feel of how it manifests itself, but I do understand to a point your attached graph.

Fair enough.

See also : 'Anti-Stall Feature'
https://www.fiatforum.com/threads/anti-stall-feature.182588/post-1967587

 

[The Panda Nut]

I have been around diesels for all of my 50 years of driving commercial vehicles, and to be honest have never come across this on any diesel engined vehicle I have driven and operated, and that ranges from light commercials through to 44 ton articulated lorries. But... I have not driven Fiat Ducatos until now, is this really normal for any Fiat Ducato, either a Motorhome or a commercial vehicle? with that clarification answered, then I shall stop thinking of it as a potential problem and just enjoy the vehicle for what it is

Well if your familiar Im sure your gut feeling on it will be correct. SOmeone new to diesels might find the feel very different but I woiuldnt expect the Ducato to be any different than any other similar vehicle. There isnt much to cause such issues and its not something Ive ever expereincedas a problem. Air leaks seem to be a common issue on older car engines but symptoms not quite the same. I would check oyu dont have excessive crankcase pressure and also that the oil is good and not diluted by DERV as a start. f thats good then see if the filter and bowl seals are present and correct. What you describe has not been raised on here that I have noticed for what that is worth. Id find another similar vehicle and test drive it. See what it feels like.