The engine starts immediately but refuses to exceed 1200 rpm for 1-2 minutes, then suddenly the engine sound changes from muted to normal and it responds like it should. This happens regardless of engine temperature, once the sound changes the exhaust produces an alarming amount of smoke with an acrid smell.

The phenomenon began immediately after the fuel filter cracked open and poured more than half the tank's content over the engine. I posted about that a few days ago.

The warning light came on with an error code for "excessive EGR". I deleted the code, the light is off, but the problem remains. I also tapped on the EGR valve with a small hammer, at the same time applied compressed air to the vacuum hose and plugged it: no improvement!
Removing the valve seems a lousy job because of the location of it, the rusty bolts and nuts and the fact that it is connected to the coolant circuit. And frankly I'm not sure the valve is really the culprit.
I read somewhere there is also a "throttle housing", something I do not understand because diesel engines normally do not have such a device.
Can anyone shed some light on this?

The throttle body is at the front of the engine on the right hand side looking from the front. It is bolted to the top and to the right of the inlet manifold.

It controls the amount of air let into the engine.


Mike

taffybloke said:

The throttle body is at the front of the engine on the right hand side looking from the front. It is bolted to the top and to the right of the inlet manifold.

It controls the amount of air let into the engine.


Mike

Click to expand...

That is exactly what I do not understand because normally a diesel engine has no throttle! There must be a reason why Fiat uses it while other manufacturers don't, but I can't figure it out.

It may be that it stays fully closed when the engine is started, causing the problems.

For now, the van is parked in our garden and will not move one inch until the mystery is solved.

Throttle bodies are common on diesel engines. Most manufacturers use them.


Mike

Just nicked these pics off eBay, this is a euro 5 one (2011 on) but looks exactly the same if I remember right, my old 2.3 120bhp 07 plate had one go, the butterfly seizes up an doesn't move freely due to coke build up and knowing ducatos probably from water ingress too!

Just an added note, I'm unsure on any technically knowledgable folk on here can confirm if I'm right,

But since my throttle went (aprox 70k miles) I once a month popped 2 bottles of comma diesel manic inj cleaner in before fully filling tank up also as I have a BP & Shell fuel cards I'm only using "quality" diesel not supermarket diesel, sainsburys diesel used to throw up EGR faults so stopped using the stuff, faults stopped occurring after switching back to main brand fuel, I heard the quality is of an older spec diesel, less or no cleaning additives and poss other missing ingredients,

End of day I completed over 200k more with no Egr or throttle body faults since

On a German camper forum I found 100's of posts about this topic. Most were complaints about the excessive repair bills and/or incompetence of Fiat mechanics, but I also found a few facts.

The throttle valve serves two purposes: creating a vacuum so exhaust gases are drawn in to reduce NOx emission and to quickly stop the engine without too much shaking.
This all makes sense to me; the turbo charger pressure would prevent EGR if the throttle valve wasn't there and the engine might keep on going for a while after being switched off because the oil pan fumes contain unburnt fuel.
The two VW turbo diesels in my boat do not have throttle valves but also no EGR.

I discovered that instead of waiting 1-2 minutes after starting, normal operation can also be obtained if the engine is switched off and restarted immediately! But as soon as I feel up to it I will remove the whole throttle unit and thoroughly clean it.
The EGR valve has its vacuum port blocked now so it will not make problems anymore.

I agree with rolopolo, I only use branded diesel since we had an issue with the EGR and Redex every few tank fulls.


Costs a bit more but cheaper than EGR's


Regards

In my country there is no such choice. Fuel comes from only two sources and is sold under brand names only for a government dictated price.
There is lead free diesel and premium lead free diesel with a very small price difference. There is zero information about chemical differences (if any).
With a camper van traveling through Europe you get all kinds of fuel, different colors, smell and pricing. You can avoid buying fuel in a country like Italy where pricing is outrageous, unless you plan a long trip there.

Believe it or not: I am not a violent person. I prefer strategy over brute force.
Also I seldom curse.
When things take a turn for the worse, I light a cigar and think about a solution.

But today was an exception.
I have spent the better part of the day trying to remove the throttle valve. The Fiat workshop manual for the X-250 chassis I purchased on a CD seems to be written by a guy who never used a tool in his life. It says that you should remove the negative battery cable, an air hose and then you can remove the throttle valve.
Outright lies! No tool in the world can unscrew bolts if there is no place to turn it.
By now I have removed the whole plastic front, the bonnet lock, the air filter housing and the metal cross member above the radiator(s) and I still cannot get the throttle valve out.
To unscrew the 6 bolts holding it I needed all 13mm spanners and sockets I have; even cut part of an already pretty short ring spanner because there was not enough room to turn it 15 degrees because the radiator is in the way.
At this time 5 bolts were removed, but #6 is at the lower left where I cannot even see it, but I know it is there because the bloody thing still prevents me from take the valve assembly out. I probably have to remove the whole radiator to get a socket with an extension on it.:bang:

I spoke to God in short sentences several times today, but that didn't help a bit.
This vehicle is designed by idiots or sadists or both!

When mine was changed the mechanic jacked the from up, he removed all he could from above, then removed bolts from underneath, whole job took about 60-90 mins, needed new extra large hose clips for the air hoses as the orig clips were unusable again, just remember having to go get some.

With the radiator dangerously forced outward I finally managed to see the bolt head and put a socket on it with a thin (1/4") extension. Instead of unscrewing the bolt head snapped off but at least I got the valve assembly out.
Removed the "motor" which is actually a rotating solenoid. The interior is badly rusted after years of exposure to rain dripping under the cleverly designed plastic lining under the windscreen that first fills up the bath tub of the cylinder head, then flows over the throttle motor. I hope there will never be the need to remove injectors because these 4 bolts also do not stand a chance.

The exhaust gas return part and the intake manifold look as if a crew of road workers dropped their excess tar in it, but since I plugged the vacuum hose there will not be any new deposits. Cleaning is out of the question unless I remove the intake manifold, but I decline.

The throttle valve motor is not for sale, just the complete assembly for a price you can buy a decent mountain bike or a color laser printer for. If I cannot restore its function I will probably jam the valve in open position and reinstall it.

Not worth the hassle, just pay for a new one, and use injector cleaner and best brand of fuel available,

And yes the injector bolts would snap off they are long bolts that drop through the cam box down to the head, I had two snap while replacing injectors. £4000 inc cambelt and service later, it turned out to be fuel pressure regulator ! Miss diagnosis by a "diesel specialist" hmmm
Just got to love fiats and the water ingress,

Two options: you are mistaken or the mechanic fooled you and exchanged the EGR valve. The throttle valve is in the picture, made when the front of the van was removed.
You see 3 hex nuts, the 4th is hidden behind the alloy elbow.
Even a guy with double wrist joints could not get it off working from under the car.

After mechanically and chemically removing most of the rust from the solenoid, the throttle valve is back in place and so are all the plastic panels, bolts and nuts that hide the innards of an X-250 Ducato van.

The engine started 1th time and responded to the accelerator pedal like a new one, so the repair was successful!

To all Ducato owners who had, have or will have throttle valve problems, there is something I want to explain.

If you think tampering with or complete removal of this part has consequences for an exhaust gas test, don't worry, the device does NOT work anyway. Fiat says the valve works in cooperation with the EGR valve, but that is a fairy tale. There is no position sensor and no feedback to the ECU. The valve is always open, except when the engine is switched off: then it closes briefly to stop the engine more quickly.
This imho is a totally useless function, not worth the money for a replacement valve. I really don't care when the engine makes a few revolutions more.
It just might be that more recent models have a different valve and additional wiring, but in my van it is an optical illusion that does nothing to reduce emissions.
Had I known that before I would simply have removed the air hose, jammed the valve in open position and pulled the plug from the solenoid.

Yep, that's the part, the mechanic didn't rip me off! As I was in possession of the old unit as he fixed the new one in, he also is a Peugeot Forman although the Peugeot engines are different he knew exactly what, where and how.

I suppose it's down to the individual as to wether to replace or repair, all I know is once replaced, and using BP & Shell diesel, injector cleaner once a month, and bearing in mind my van is my income, and covers 100,000 miles a year
It's more than a safer bet to replace the unit for peace of mind than repair and hope that in a few miles you don't find out the unit was damaged/worn and has to come off the road again, costing more than just another mechanics & parts bill.

Hope yours runs forever mate, just watch the quality of fuel etc you use, and how it's driven (stop start urban usage or motorway miles where it gets a clear out)

CDK said:

There is no position sensor and no feedback to the ECU. The valve is always open, except when the engine is switched off: then it closes briefly to stop the engine more quickly.

Click to expand...

The valve when is operates correctly is supposed to help control the ratio of exhaust gas to fresh air, the egr circuit is restrictive and without the throttle valve the maximum egr ratio will be low as the engine will pull most of the air through the less restrictive intake. The ecu calculates the valve actuation from a table, it 'knows' the requested egr opening, and knows the maf reading theres the feedback.

You're only going to see it closing off in situations where lots of exhaust gas is called for.

Also if your turbo explodes it should stop the engine running away on its own oil and throwing a rod through the block.

If the van were my income I would make different decisions; of course I would have defective parts replaced by new ones. More likely I would have traded it for a Mercedes or something Japanese.

But in my case the van is used to spend money, not to earn it. And for spending money it does quite a job, just not what I had in mind when I bought it in 2009 at an auction for Adria motorhomes employees. It was a factory test vehicle used for exhibitions mainly and had done only 22000 miles. There were only a few such vehicles built, both LH and RH versions, but the market response was negative, so the factory abandoned the project.

From the 40000 miles we covered I remember the following events:

-Flat tires on both rear wheels. Fiat uses metal valves for the front wheels and rubber ones at the rear. These dry out in sonny climates.
-A front wheel rim cracked near the valve hole.
-Both head lamp units were replaced because of water ingress.
-3 times large quantity fuel leaks from the filter, each time in remote mountain areas.
-fuel filter housing replaced after massive fuel leak from a crack.
-front wheel bearings and one steering knuckle replaced because of excessive play.
-Premature tire change because of uneven wear.
-Rear brake discs, pads and bearings replaced.
-Battery negative cable replaced (manufacturing defect).
-Cabin air conditioning failures, finally solved by replacing a hose near the compressor.
-EGR valve and throttle valve defects.
-Various interior parts like the dashboard locker and arm rests. The plastic gets brittle and parts fall off.
-The vehicle is in the process of shedding its skin like a snake. The white paint falls off in flakes.

I omit problems with the interior like gas leaks and furniture collapsing because these aren't Fiat parts. And also damage caused by vermin gnawing at essential wiring like the leads to the alternator.
Most of these issues happened while on long trips abroad and caused lost days or made us decide to cancel part of the trip.

This is not the first Fiat I owned. The 124 spider also was a lousy product that spent more time at the dealer than any other car I owned, but that was a long time ago.

ecunotemu said:

The valve when is operates correctly is supposed to help control the ratio of exhaust gas to fresh air,

Click to expand...

That is the explanation in the "eLearn" Fiat workshop manual.
But the reality is different. Pins for position sensing of the throttle valve aren't there, the valve only has 2 positions, open or closed. The motor is no motor, just a rotating solenoid.
If it should close while driving the engine gets only exhaust gas and suffocates!

As I wrote earlier, it may be that later models have this system truly implemented, but on my 2007 Ducato MJ-120 it is not.

CDK said:

That is the explanation in the "eLearn" Fiat workshop manual.
But the reality is different. Pins for position sensing of the throttle valve aren't there, the valve only has 2 positions, open or closed. The motor is no motor, just a rotating solenoid.
If it should close while driving the engine gets only exhaust gas and suffocates!

As I wrote earlier, it may be that later models have this system truly implemented, but on my 2007 Ducato MJ-120 it is not.

Click to expand...

Maybe yours is different to all other vehicles with a throttle electrovalve. Ecu driver for that pin may be shorted.
Forget about position sensing. It doesn't need position sensing its pwm modulated just like the pressure regulator in the pump or the idle air control valve in a petrol car. Like those the actual position is irrelevant its the result that matters. The pwm signal is varied until the required result is achieved.