The Dispatch | Expert | Scudo Hub

Jowettdriver

Member

From: Norwich

Registered: 2018-09-27

Posts: 15

Surging under acceleration.

Hi Guys,

Any ideas on this one??

Used my van up until August of last year and then the MOT expired and it stood unused until Christmas. I have now started using it again properly and noticed a problem it hadn't had before, it has started to surge under acceleration. Once the boost comes on at about 2000rpm it starts to take off in its usual way but then hesitates, then it accelerates strongly again, and then hesitates, it does this 3-4 times between 2000-3000 rpm. The other thing is it has always seemed a bit gutless below 2000 rpm, I know all turbo diesels are a bit that way but this seems worse.

As the van is slowly being converted into a day van I'm going to be using it to tow our caravan. This weekend just gone was its first outing towing, a nice trip from Norwich to Pontefract and back and it became apparent this was more of a problem than I thought. With 1000kg of caravan it would not pull 3rd, 4th or 5th at anything less than 2000rpm, and the hesitation in the acceleration was clearly a problem. Then to cap it off on the way home while on one of its good moments it split a turbo hose - doh! It happened on an uphill stretch as I was passing a layby so pulled straight in. Half a mile of gaffa tape around the hose got us home using back roads and keeping the boost right down.

I'll replace all the flexible hoses in the boost pipework but I just wondered if anyone had any experience with this surging problem? I have changed the fuel filter thinking fuel starvation and that hasn't fixed it.

Just to clarify, 2004 Fiat Scudo, with the 2.0 HDI engine, 120000 on the clock.

Thanks in advance

Tim.

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2004 Fiat Scudo 2.0 JTD SX

vaz2121

Member

From: Glasgow Living:~ SW. Scotland

Registered: 2015-08-31

Posts: 1,311

Re: Surging under acceleration.

My van is non turbo but I did once have a 2.0HDI 307 that made my life hell for about half the year....Can I Say this and you have a think about it...... It didn't surge right enough, Just Shi* or no boost .............. it had separate little Vacum boost controlers with a variable vane turbo rather than the normal mechanical hung on the side of turbo with a rod type ........ It turned out to be a turbo issue in the end... but not after being told change vacum boost control and fuel Rail pressure sensor ......... Question is  do you have variable vane turbo? and is this a version of what they thought I Had..........

Personally it sounds like after a certain boost pressure is reached you as experienced a possable boost leak .... but is resealing and away we go again repeating the cycle.......... 
Or a faulty sensor doing much the same {thinking overboost maybe ?}.........

Last edited by vaz2121 (2020-03-03 14:58:59)

Jowettdriver

Member

From: Norwich

Registered: 2018-09-27

Posts: 15

Re: Surging under acceleration.

Thanks for your reply.
As far as I know these do not have a variable vane turbo, just the normal wastegate with rod. That said I'll take a look at the weekend when I have it up on the lift.
I had wondered about a small split opening and closing causing the fluctuations so I think I'll replace the split hose and then take it for a run.

I have recently got hold of one of these Gauges that plug into the OBDII port, so I can get that to show manifold pressure and give it some beans and see what the boost pressure does.
Cheers Tim

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2004 Fiat Scudo 2.0 JTD SX

vaz2121

Member

From: Glasgow Living:~ SW. Scotland

Registered: 2015-08-31

Posts: 1,311

Re: Surging under acceleration.

As far as I know these do not have a variable vane turbo, just the normal wastegate with rod.
Cheers Tim

I think you could be right Ive been learning over this last few years that the passenger car got lots of shi* the vans didn't ...(And it seems not exclusive to just PSA Vehicles either)..... i.e.DPF's..... which of course makes lots of sense as a car does so much more in pollution than a van out working all day and night in town

Wizzer

Member

Registered: 2019-11-26

Posts: 12

Re: Surging under acceleration.

I recently had the exact same symptoms with my 2.0hdi Expert. Drove normaly then under hard acceleration it surged and was really noticeable! For me, it was a faulty MAF. Determined this by cleaning the old one and the surging minimised but was still present. I bought a used OEM one from ebay for £10. Took 5 mins to fit and now there is no surging at all and she accelerates smoothly again.

Jowettdriver

Member

From: Norwich

Registered: 2018-09-27

Posts: 15

Re: Surging under acceleration.

I recently had the exact same symptoms with my 2.0hdi Expert. Drove normally then under hard acceleration it surged and was really noticeable! For me, it was a faulty MAF. Determined this by cleaning the old one and the surging minimised but was still present. I bought a used OEM one from ebay for £10. Took 5 mins to fit and now there is no surging at all and she accelerates smoothly again.

That's interesting thank you.

Finally had time to change the turbo hose which means I can use all the boost again, unfortunately this has not fixed the surging issue. I have one of those gauges that plug into the OBDII port and you can cycle through and see real time feeds of different information while driving so I have plugged it in and asked it to show absolute manifold pressure. What does surprise me is that when accelerating hard in fourth or fifth I can see readings of up to 36psi, which is up to 21psi of boost, this to me seems quite high for these engines, in my experience most "low performance" diesels tend to have no more than 15psi of boost. Does anyone know at what pressure the wastegate is supposed to open?

What I was wondering is  if one of the vans previous owners has messed with the wastegate in a ham-fisted attempt to get more power and the management system is detecting an overboost and then backing off the fuelling causing the surging effect.

I think from here I will try cleaning the MAF like Wizzer suggested and see if that makes a difference, if it does I'll change the MAF and see how it goes. If that doesn't help I might see if I can easily adjust the wastegate pressure back to 15psi of boost and see if that helps.

Cheers Tim.

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2004 Fiat Scudo 2.0 JTD SX

Wizzer

Member

Registered: 2019-11-26

Posts: 12

Re: Surging under acceleration.

Forgot to mention too. Try running with your MAF sensor unplugged. Mine ran smoothly indicating a faulty MAF. Sorry I missed this bit out!

Jowettdriver

Member

From: Norwich

Registered: 2018-09-27

Posts: 15

Re: Surging under acceleration.

Forgot to mention too. Try running with your MAF sensor unplugged. Mine ran smoothly indicating a faulty MAF. Sorry I missed this bit out!

Thanks Wizzer, you were spot on!!
Disconnected the MAF and it now runs perfectly, in fact it drives so much nicer then it ever has in my ownership. Picks up from low down, no surging under acceleration, it even seems to run smoother. New MAF ordered.

Thanks for your help everyone.

Cheers Tim.

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2004 Fiat Scudo 2.0 JTD SX

Wizzer

Member

Registered: 2019-11-26

Posts: 12

Re: Surging under acceleration.

Glad I could help.