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Old 03-02-2012   #1
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Multijet - Loss of power on full throttle

Hi. My wife's multijet has just started playing up again. 56 plate, 39,000 miles. Car starts and runs well right up to 80 odd mph. However, if you slow down, and then accelerate hard, as in overtaking, there is a noticeable lurch, and the engine management light comes on. Power then seems to be down around 25%. If I stop, and start then stop the engine four times, the engine management light goes out, the ecu resets itself, and everything is back to normal. Before I get involved with our local dealer, Arnold Clark, I thought I'd see if anyone else has had this problem. Perhaps coincidentally, I noticed that something ( mouse? ) has chewed the sponge on the bottom of the air cleaner element. I've checked all the airways in case some stray sponge is blocking one up, but all appear to be clear. I'm guessing that the hesitancy problem is related the the MAF air sensor. Any ideas welcome.

Colin
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Old 03-02-2012   #2
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Re: Multijet - Loss of power on full throttle

turbo waste gate linkage is seized
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Old 05-02-2012   #3
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Re: Multijet - Loss of power on full throttle

Quote Originally Posted by notsmartcars View Post
turbo waste gate linkage is seized
Is that just a guess, or have you experience of it? Any tips on how to free it off?
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Old 05-02-2012   #4
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Re: Multijet - Loss of power on full throttle

Does it have a wastegate?
I thought they were Variable Vane Geometry jobby that don't have or need a wastegate.

Maybe the actuator has seized, but the first port of call for me would be EGR valve.
These are a real pain for the modern diesel engines.

As the MIL as illuminated, it should have stored a code (though after 3 clean starts and warm ups could have cleared it's self)
It's worth the cost of a code read.
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Old 05-02-2012   #5
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Re: Multijet - Loss of power on full throttle

There are loads of threads on this forum for this problem now.... of course a code reader is the way to go but you can check the waste gate diapham/linkage just pull off the small pipe to the actuator connect to air line and if the rod has not moved out by 20psi that will confirm the problem.
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Old 05-02-2012   #6
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Re: Multijet - Loss of power on full throttle

I think you may mean the actuator arm may be seized.
VGT's don't have wastegates.

I think it may be the EGR valve stuck open.
39k sounds a bit low for the year, so I can only guess the car is getting "local and light use" and probably hasn't had the gunk blasted out of it with long motorway runs.
It's a very common issue with common rail diesel engines as they've tried very hard to clean up their emissions.

Soot and oil vapour from the crankcase breather (which will feed into the air intake somewhere along it's route, again sent in there to burn to clean up emissions) get blown up to this valve, mix and cause a right mess, gumming the valve up like this
http://t3.gstatic.com/images?q=tbn:A...MJdabtY8fKXbWE

The OP seems to say the car runs ok up to a point, then when it's floored it stutters, loses power and lights the MIL, seems to point to the turbo being ok until something else happens.

When the car has an open throttle the egr valve should be firmly closed (it should only open on part throttle like a steady cruising speed and under certain conditions to lower combustion temps which lead to cleaner emissions, The sort of speed and load the valve should open, could or could not have something to do when emissions measurements are taken!! You make your own mind up )

If the valve is sticking open and the pedal gets floored, it'll stuck in a load of exhaust gases which are full of Nitrogen Oxide instead of all the air it needs to burn the fuel it's just dumped in there.

The NOx won't allow the fuel to burn as well as air.
It's not good at allowing combustion, think back to fire training, take away either the fuel, heat or oxygen and the fire goes out (the fire triangle), well NOx takes away oxygen and heat.
NOx also cools the combustion that does take place, add both effect together and it'll lead to the hesitation, loss of power and in some cases the MIL lighting up, it's effectively choking it's self on exhaust gases.
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Old 05-02-2012   #7
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Re: Multijet - Loss of power on full throttle

Quote Originally Posted by Goudrons View Post
The OP seems to say the car runs ok up to a point, then when it's floored it stutters, loses power and lights the MIL, seems to point to the turbo being ok until something else happens.
It is usually the VGT gubbins sticking, which results in over-boost and the ECU cuts power to save the engine.
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Old 05-02-2012   #8
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Re: Multijet - Loss of power on full throttle

Sorry I thought the problem was on a 1200 diesel multijet panda which has a waste gate built in to the turbo housing letting excces boost pressure release in to the exhaust system contolled by an actuator fed by a pipe in the inlet feed system... I dont know what a VGT is Ive put my coat on and getting ready to run
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Old 05-02-2012   #9
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Re: Multijet - Loss of power on full throttle

Quote Originally Posted by notsmartcars View Post
Sorry I thought the problem was on a 1200 diesel multijet panda which has a waste gate built in to the turbo housing letting excces boost pressure release in to the exhaust system contolled by an actuator fed by a pipe in the inlet feed system... I dont know what a VGT is Ive put my coat on and getting ready to run
VGT = Variable Geometry Turbo.
The geometry of the turbo changes to vary the amount of boost produced and they use that instead of producing everything and dumping the excess.
But when the clever stuff sticks with the amount of crap these engines produce the result is too much boost and the ECU cuts the engine to stop something very nasty happening.
You get exactly the same thing when a wastegate sticks.
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Old 05-02-2012   #10
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Re: Multijet - Loss of power on full throttle

Ta David C forums are marvellous
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Old 05-02-2012   #11
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Re: Multijet - Loss of power on full throttle

Quote Originally Posted by Goudrons View Post
Does it have a wastegate?
I thought they were Variable Vane Geometry jobby that don't have or need a wastegate.
I think only the 90hp Multijet has a variable vane turbo, the 70/75hp versions have a standard turbo+wastegate combo.
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Old 06-02-2012   #12
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Re: Multijet - Loss of power on full throttle

That's why I asked if it had a Variable jobby, though it's very common to fit them to CR diesels these days.

I've not got the Multijet version, but a CR diesel from a different manufacturer and with it go all the common problems of the modern diesel engine. (we decided the petrol Panda was a better bet for our short, city trips)

I believe some VGT's can release some exhaust pressure through the EGR, though at what level and when isn't clear. I've never experienced this or read of any problems regarding it.

This does go against the operation of the EGR as it should in fact be closed on high throttle when boost pressure is at it's highest.
The car's gone to a lot of effort to suck in, filter, boost and cool all that air to kick you along and then the egr stuffs a load of Nox in there to choke it, this does seem hard to fathom if it's designed to work like that??

This is the fact I was pointing to as a possible fault, if it is sticking open at full throttle the gases which aren't meant to be there will effectively choke the life out of the engine.

Actuator arms have been know to seize, but as stated I'm unfamilar with the Multijet, with mine you can manually move it back and forth to test it's movement, I see some manufacturers have moved from vacuum to electronic actuation, which has caused some trouble.

I can see there would be issues with a system that releases "over pressure" via other means, like dumping them back into the exhaust flow if in fact it's actuation does seize, this is why I'd have thought it would have been a VGT, there would never be a "over pressure" problem with that set up and the vanes alter angle to adjust boost.

By far and away the biggest gripe on nearly all CR's these days is the EGR.
I count myself luck my EGR is an old style vacuum operated one that isn't connected to the ECU via a sensor or run off a little motor, I can restrict (or block completely) the exhaust gases it releases without trouble and save myself the headache. (I can also alter the route of the CCV blowby away from the air intake to reduce the likelyhood of gunk blocking it altogether.
I think this isn't the case with euro 5 cars, sensors will monitor the EGR flow rates and anything outside their limits and it will light the MIL and log a code.

It's usually very obvious to see if it's a suspect EGR by removing it and looking at it's state and if you're handy with the spanners it free to check and clean (filthy job), though if it's sensors or motors (if in fact it has them) are damaged it my not be so obvious.

As the OP car is throwing a MIL, it would be interesting (for me) to know what the code is.
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Old 06-02-2012   #13
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Re: Multijet - Loss of power on full throttle

Hi. Thanks for all the comments. It does look like the next move is to get the car to the dealer, and get the fault code read. Incidentally, the car does two 80 mile motorway trips per week, so I would have thought enough to clear the worst of the soot out, but maybe not. I'll make sure it "performs" and make sure that the engine management light is still on when I get there.
Thanks

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Old 06-02-2012   #14
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Re: Multijet - Loss of power on full throttle

Don't forget to post what's found.
Often posts die when problems are solved without the resolutions being posted.

I'm sure this will help others.
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Old 06-02-2012   #15
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Re: Multijet - Loss of power on full throttle

Quote Originally Posted by Goudrons View Post
I can see there would be issues with a system that releases "over pressure" via other means, like dumping them back into the exhaust flow if in fact it's actuation does seize, this is why I'd have thought it would have been a VGT, there would never be a "over pressure" problem with that set up and the vanes alter angle to adjust boost.
When the vanes in a VGT turbo stick it results in overboost and the ECU cuts the engine.
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