Poor throttle response and engine a bit flat

[SAlexander]

Hi all, one for the more technically inclined.

I'm trying to track down a problem in my recently acquired Rapido 640F. The initial throttle response seems very flat, when pulling away from a junction you seem to need a lot of throttle to get much acceleration. Once you get to about 40-50% throttle pedal movement, you can distinctly feel a bit of turbo boost kicking in and performance is ok. Similarly, when cruising, you seem to have the pedal quite far down to maintain motorway cruising speeds. Fuel consumption also seems to be a few MPG less than I would expect.

This is all in comparison with a couple of previous Fiat vans where the throttle was perfectly linear in response and there was never any feeling of turbo boost kicking in. The Rapido is 2015, Ducato 130, Euro 5+ with 10k miles. There are no engine lights showing and no stored codes. However, a scan of the sensor data on OBD shows that the Accelerator absolute pedal position is 19% at idle and only gets to 83% with the pedal to the floor.

My motorhome dealer has checked it and are happy that the performance of the van is 'normal' and their scans have shown no faults. They have suggested that the engine may still be a bit tight, which admittedly does seem to be a recognised characteristic of these engines.

However, I'm struggling to accept that the throttle pedal position info is correct and that this wouldn't have an affect on engine performance. I'm aware that many modern vehicles have a throttle pedal 'learn' function so that you can effectively re-programme the pedal travel in the ECU, but can't establish if this exists for the Ducato.

may have to get it checked out by a Fiat dealer I suspect, but any thoughts gratefully received!

[thebishbus]

Have you checked for any splits in the turbo outlet hose . If you squeeze the hose it should swell as you rev up.

Brian B.

 

ps Welcome to the Forum.

[K2 Rum]

I had a similar issue on a diesel Volvo. The Air mass sensor needed changing. This determined the turbo performance. i would have thought a diagnostic would find that however, but Fiat may be a better bet than a MH dealer, however good.

[Derek Uzzell]

Stephen

 

As you’ll see from the infomation on the left of this posting I also own a 2015 Rapido 640F. This is left-hand-drive, with the 150 motor and manual transmission.

 

Although it’s to be anticipated that a brand-new motor’s performance will improve after some mileage has been covered, 10K miles should be more than enough distance for a Ducato powerplant to be fully ‘run in’. In fact, I would have thought that a 5K mileage distance should be plenty sufficient.

 

The 150 motor has a variable-geometry turbocharger and this complicates direct comparison with the 130. But as you’ve owned Fiat vans previously and know that those vehicles did not react to the throttle in the manner you’ve described, it certainly sounds like something is amiss.

 

Presumably the condition of the air-filter has been checked, as a contaminated filter would affect fuel consumption (though probably not produce the sort of ‘turbo lag’ behaviour that you’ve been experiencing).

 

There are a few Ducat-related on-line references to a faulty accelerator-pedal potentiometer causing problems, but those problems don’t really match yours. I don’t think there’s anything ‘smart' about how a Ducato responds to accelerator-pedal movement (at least not with manual-transmission vehicles).

 

A Fiat Professional (FP) dealership with plenty of Ducato experience OUGHT to be able to know if how your vehicle is reacting to the throttle is ‘normal’ and, if not, (hopefully) what the reason is. If the lack of performance can be easily demonstrated by a road test (ie. get an FP technician to drive your Ducato while you explain what happens) that should help.

[colin]

Derek Uzzell - 2019-11-14 5:06 PM

 

 

Presumably the condition of the air-filter has been checked, as a contaminated filter would affect fuel consumption (though probably not produce the sort of ‘turbo lag’ behaviour that you’ve been experiencing).

 

And checked for mice.

[SAlexander]

Thanks all. The van was serviced as part of the dealer prep and I have checked the filter - new and clean and no evidence of mouse habitation :-D Similarly, hoses are all in good condition as you would expect and no obvious signs of hisses or air leaks.

 

The van starts no problem and runs cleanly with no smoke or any other issues and is consistent in the way it performs. I forgot to mention that I swapped out the throttle pedal with another known good unit and the sensor readings were exactly the same.

 

The ECU sensor data shows two 'Absolute pedal position' outputs - I 'think' that these represent outputs from different tracks in the throttle potentiometer, with one going to the ECU and the other to the throttle body. Both readings are the same, which again seems to confirm that the pedal is just fine.

 

A miscalibrated throttle pedal just seems to fit the scenario to my mind, but I can't seem to find any info on how to do a manual reset (if it's possible) or via an appropriate scantool (inevitably a far more sophisticated professional tool than the one I have!).

 

Not unusually, the van did sit on the dealers forecourt for a few months, so there is the potential for things seizing, getting damp etc.

 

 

 

[SAlexander]

Forgot to say - I have to agree on your point about running-in Derek. I've seen a few online references to engines remaining tight until 10-15k if they have been treated 'too' gently. This seems quite counter intuitive - engines can be built to manufacturing tolerances unheard of in the clunkers we drove years ago, hence there is generally little need to run-in modern engines. Also, a tight engine is hardly conducive to the constant drive towards greater fuel consumption and lower emissions.

I've been involved in motorsport most of my life - when we build new race engines they generally get run-in on the dynamometer over a short period at quite high revs, being gentle isn't good for them :-D

[BIFFO]

Hi to all. Think I can relate a little to this problem. I recently changed my van for a corado Vlow. There was just 180 miles on the clock when I took delivery. The van was full of diesel when I collected it. All fine for the time I had near emptied the tank. Put 50e of diesel from a prolific supplier of diesel and went about my business. After a100/150 miles I found the van reluctant to accelerate smoothly. There was a slight delay in take up when been driven on. Rang the dealer who unfortunately is a three hour drive away and reported same. Anyway to get to the point. Was talking to a hgv mechanic ...........told him my story .............asked where I got my diesel. Told me to change to a different diesel supplier. I did so and it has worked. Van runs smoother and acceleration is clean and responsive. I have not yet checked ratings or quality of the diesel but as it working fine I'll leave well enough alone.

That's my tuppence worth. Safe driving.

[SAlexander]

Thanks Biffo, that had occurred to me, especially with the van sitting unused for a while. So I put a tank of Shell V-Power in it initially and it has had a couple of refills since with no obvious change in performance.

[onecal]

Yes poor Diesel does not help,,,,as BIFFO suggests and is common in his neck of the woods. Hopefully not in yours but it's a very good point to check and often overlooked. 

I would advise to check your wiring loom and connections thoroughly

(break and close) pull apart and reconnect the connections a few times and check wiring loom for damage. 

Of course you can always get the throttle pedal custom tuned  

[Derek Uzzell]

onecal - 2019-11-14 7:05 PM

 

...Of course you can always get the throttle pedal custom tuned  

 

Yes, and there are several suppliers of the equipment to do this (example here)

 

https://www.advanced-incar.co.uk/products/vehicle-tuning/dte-pedal-box-throttle-response/

 

I was going to suggest that, if the cause of the problem were the accelerator-pedal itself, replacing it might provide a cure - but Stephen has already tried that.

 

Stephen thinks that the problem may lie with how the ECU is interpreting the pedal’s outputs and is wary of the 19% and 83% adsolute pedal position readouts obtained via the OBD port. To confirm whether the 19% or 83% figure is wrong, it would be necessary to establish what the correct datum should be. A Fiat agency might know; otherwise taking pedal position readings from other similar-age/similar specification Ducatos should be a valid comparison ploy.

 

The motorhome’s previous owner might be prepared to say if he/she had noticed this problem, and dynamometer testing would confirm whether the motor’s performance is ’normal’. Me, I’d start by asking a friendly Fiat Professional agent if they had encountered this phenomenon before and if ‘recalibration' of the throttle pedal is practicable.

[tonyishuk]

Just a wide shot and passing thought !!

 

Not the Rapido wandering carpet syndrome ?

 

Ours suffered from this as the carpet moved between the floor stop and bottom of the pedal.

 

Rgds

[SAlexander]

Throttle 'tuning' boxes really are a bit of a scam! They can't improve performance in any way and simply remap the pedal position to the amount of power you get from the engine. Typically they would be set up to increase the rate of throttle opening at the earlier part of the pedal movement, so the car feels more 'urgent' and gives the impression of better acceleration. In my case it wouldn't help what I think is an underlying problem.

 

I have checked my previous van and, as expected, the throttle sensor readings show 0% at idle and 100% with foot to the floor. Carpets checked and no issues - this might affect the ability to get full throttle but wouldn't explain the 19% reading at idle.

 

The search continues!

[onecal]

Again check all connections and wiring loom,including all earths. Check ECU pins 8 and 9,Also check your battery or replace and then check your voltage on idle, then if that fails have the ECU checked

[skaman]

Start with the simplest and cheapest possible remedies and replace the fuel filter. It may have sucked up a lot of crap from the bottom of the fuel tank. Fixed mine.

[onecal]

Hi Stephen,

I am assuming you have already done a quick throttle pedal calibration yourself to clear the ECU memory of the old one when you replaced with a replacement one?

Again all connections and sensors need to be checked along with the wiring loom and battery voltage,

You can of course try a manual re set 

 ECU Accelerator Pedal Reset Procedure

 Note Timing is critical for this to work! 

1. Turn the ignition switch to on. Dash gauges lit. Don t start the engine! 

2. Wait 3 seconds. 

3. Fully depress and release the accelerator pedal 5 times within 5 second. 

4. Wait 7 to 10 seconds.

5. Fully depress the accelerator pedal for approximately 10 seconds. 

6. Release accelerator pedal and wait 5 to 10 seconds. 

7. Fully depress the accelerator pedal for 10 seconds. 

8. Release the accelerator pedal and turn the ignition switch to off.

9. Restart the engine. 

[Keithl]

onecal - 2019-11-15 7:17 PM

 

Hi Stephen,

I am assuming you have already done a quick throttle pedal calibration yourself to clear the ECU memory of the old one when you replaced with a replacement one?

Again all connections and sensors need to be checked along with the wiring loom and battery voltage 

 

Onecal,

 

Unless you are actually using the editing features of 'Rich Edit' please can I request you turn it off in your User Control Panel.

 

'Use rich edit box when composing messages?' should be set to 'No'.

 

Rich Edit makes the font a grey colour and smaller size then normal.

 

Thanks.

Keith.

[onecal]

Thanks Keith,

My apologies

Kind Regards

Brendan

[Keithl]

onecal - 2019-11-15 8:21 PM

 

Thanks Keith,

My apologies

Kind Regards

Brendan

 

Much better :-)

Thanks.

[spirou]

I can't remember if I've seen the odd throttle position readings in my car or our previous citroen euro5 130hp van, numbers might have been about the same as you state. Regardless, neither seemed to me as being affected by it in any way so I somehow doubt that would be the reason for the poor response.

 

I guess you could try test driving a MH or van with the same engine and see if there is a difference.

[SAlexander]

Hi Onecal, thanks for that.

I had disconnected the battery for a while after changing the pedal, but what did you have in mind with 'doing a quick throttle pedal calibration to clear the ECU memory?

I have tried the manual reset procedure you suggested (several times) with no obvious change.

 

 

[Derek Uzzell]

Instructions on how to perform an ECU accelerator pedal reset are given in several places on-line. This link relates to a reset for a Nissan Infiniti car

 

https://uprev.com/documentation/Resets-for-Nissan-Infiniti-Functions.pdf

 

Would this procedure (or something very similar) also be effective for a 2015 Fiat Ducato?

[onecal]

Again

I would check out the wiring loom and connections thoroughly first and all reference voltages are correct. (5V)

Sometimes something very simple can throw things out of kilter finding it may not be so simple ,,

i am surprised the manual reset has not helped to remove your % reading from the ECU that you interpret as incorrect. Difficult to diagnose without seeing and knowing what work previously has been carried out to the vehicle. Re trace all your own steps and re do all again paying special attention to all connection pins for damage from condensation

Check and recheck all the simple things first, I take you have checked fuel supply and pressure as in exhaust back pressure and associated sensors.

If you have re checked all yourself and can find no faults (may be very simple one) have ECU and associate

wiring loom and connections checked by a good technician

Sorry for not been more of a help