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Technical turbo boost sensor

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Technical turbo boost sensor

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notsmartcars

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My Panda diesel has the following fault show up on my reader ..Turbo Boost sensor A circuit high.. The symptons are it drives lovely till 3000revs or around 80 mph then its looses about 30% power through the rev range, the engine management warning light comes on and then it wont go above 70ish on the flat. When the engine is turned off and restarted although the warning light stays on the full power returns unless I go above 3000 then loss of power returns ..can the turbo supply too much boost.. can the sensor be faulty and if so where is it... Ideas please :confused:
 
Boost sensor can be faulty. If it is, it's not too expensive to replace.
Mine went when just out of warranty.
 
notsmartcars said:
can the turbo supply too much boost..
Click to expand...
The turbo can supply too much bosst if it's a VNT (variable nozzle technology) turbo, rather than the more traditional setup of turbo plus wastegate. A VNT turbo modulates the amount of boost created, rather than dealing with excess boost. A VNT turbo doesn't have a wastegate.

A VNT turbo uses vanes around the circumfrernce to direct boost pressure to different parts of the impeller. This move via a vacuum operated actuator. If these vanes get sooted up they can jam open leaving the turbo in a maximum boost setup which can lead to too much boost being generated and ultimatley turbo failure.

We've changed three this month already - two on Audis and one on a BMW.

Whether the Panda diesel uses a VNT turbo or normal setup I don't know, but to answer the question, yes too much boost can be generated.

Ben
 
I have replaced the pressure sensor ( the one in the inlet manifold £29) and the fault remains so I presume the pressure is too high.. When I drove her last night I put my foot down in top at 40 she pulled lovely then I noticed in my mirror because a car was following me in the dark as It got to 70 an increasing smoke haze at followed by power cut .. so next question does the EGR valve when its working correctly restrict the turbo air flow in to the engine but if its faulty can it cause an air mixture in balance and causing high pressure on a sensor I have not found yet .. any answers thanks
 
Not sure if you've found the real problem to this, but I've already been through two MAP sensors (max air pressure), and two MAF sensors (main air flow), all done at the recommendation of various Fiat Dealers. I've since had Simonstone of Bath tell me they know how to fix it, but that they'll not tell me what they'll do. - I now know why !
The turbo on the Multijet engine is a normal wastegate style turbo, not a variable vane type, and when we took ours off for a look see, the wastegate diaphragm actuator was stuck. We couldn't shift it with a pressure / vacuum tester, but with a little leverage with a pair of pliers it came free easily. - Note that on the car, the diaphragm rod angles upwards as well, which wouldn't help if you managed to get water lying on it.
Now I've got the Panda Multijet back working correctly, no more limp home mode cutting in as you go past 3000 rpm anymore.
Unfortunately you don't get the extra boost sub 3000rpm just before the MAP sensor shouted for help, and limp home mode kicked in. - Yes, not surprisingly, there was definitely more grunt than usual.
My question now is, how does the Electronic chipping of a Multijet give more power, if they do not adjust the wastegate settings ?? - I'd have thought you still needed to get more compressed air into the engine, i.e. higher boost, to go with any extra fuelling from an ECU mod ??
Oddly, the following day a Grande Punto came in with exactly the same problem, so all we did was pull the small rubber waste gate actuator pipe off the front of the inlet side of the turbo, which is easy to get to, and gave it a couple of puffs of compressed airline air pressure, and it freed it up for the guy ASAP.
I'm just wondering how many labour hours the dealer would have charged me for the 10 minutes work it really took <grin>.
 
Like you say the fault was the actuator on the back of the turbo it was seized this can cause the turbo pressure to drop if stuck open or over boost if is sticks shut.. When it seizes shut at around 3000 the boost is so great the sensor reacts and shuts the power down I found by connecting the actuator rubber pipe to an air line even at 30 psi it didn't move so I stripped it down.. the dealer can not supply a new actuator only a new turbo( turbo technics could supply one but I would have to modify it to fit) I suspect this will turn out to be a common fault in the future..To remove its front bumper and radiator off it is possible to leave the full exhaust connected to the turbo but to refit it to the manifold its easier if you remove 6mm off the longest stud
__________________
 
Following on if I had thought about it earlier I would have fitted a gauge off a foot pump loose in the cab with a long pipe to the turbo outlet pipe then as the ecu always reset itself after tripping on start up I would see at what pressure it tripped then i could have set the actuator rod length to just under this pressure on the bench to get more power from the engine.. As it only tripped ( limp home mode) at 3000rpm around 80mph it would have supplied extra boost only when required
 
Mine had lack of power and had a new turbo installed a couple of weeks ago...
 
sellickjw said:
The turbo on the Multijet engine is a normal wastegate style turbo, not a variable vane type, and when we took ours off for a look see, the wastegate diaphragm actuator was stuck. We couldn't shift it with a pressure / vacuum tester, but with a little leverage with a pair of pliers it came free easily. - Note that on the car, the diaphragm rod angles upwards as well, which wouldn't help if you managed to get water lying on it.
Now I've got the Panda Multijet back working correctly, no more limp home mode cutting in as you go past 3000 rpm anymore.
...<snip>...
Click to expand...
I suspect my 1.3 multijet may be having the same problem (An IDEA in my case rather than the Panda, but AFAIK the same actuator & Turbo system).

I haven't got the equipment to test it "on the road" under load ... BUT looking closely at the actuator-rod through a gap in the Exhaust manifold whilst running the engine stationary, I cannot see ANY movement whatsoever of the actuator rod either at startup OR at highish revs (or anywhere in between).

I would have expected the gate mechanism to operate even whilst stationary as the Turbo should still be producing pressure (which it IS) & the Gate opening under non-load conditions ... My first query is :- Could anybody here confirm that I should be able to see the Gate/Rod operating like this, OR am I mistaken in that assumption.

sellickjw said:
Oddly, the following day a Grande Punto came in with exactly the same problem, so all we did was pull the small rubber waste gate actuator pipe off the front of the inlet side of the turbo, which is easy to get to, and gave it a couple of puffs of compressed airline air pressure, and it freed it up for the guy ASAP.
Click to expand...
I have also tried this to "free up" any potentially seized gate/rod, but without success ... The rod doesn't actually "move", although it does appear to "flex" a mm or two under airline pressure, which would also suggest a stuck wastegate or rod to me.

My second queries are :- (A) Could anybody kindly confirm whether the actuator-rod works on a "Push" principle (which is what it appears by my observations) or a "Pull" principle ... & (B) have any of the forum mechs/techs noticed that "wastegate sticking problems" MAY be becoming more common recently as these 1.3 engines "age / get older".
My lad's 1.3 is 2004 & circa 65k miles.


Another indicator that this could be my problem is that the car was working perfectly without any past problems until it was unused on ramps (in baddish weather) for a week or so whilst fitting a towbar, and the problem appeared the instant the car was rolled off the ramps and used.

Thank you kindly in advance for any advice you may be able to offer.

Cheers, Bob
 
The actuator pushes the rod out to work the waste gate ...first disconnect the small pipe off the turbo (but leave the other end connected to the actuator) then I stuck a foot pump with a gauge on into the pipe with a tapered air bed adapter then as you pressurise the pipe to the actuator the rod should move outwards at around 20 psi on mine it didnt move at all even when it approached 30psi.. hence the engine receives too much boost at around 3000rpm
 
notsmartcars said:
The actuator pushes the rod out to work the waste gate ...first disconnect the small pipe off the turbo (but leave the other end connected to the actuator) then I stuck a foot pump with a gauge on into the pipe with a tapered air bed adapter then as you pressurise the pipe to the actuator the rod should move outwards at around 20 psi on mine it didnt move at all even when it approached 30psi.. hence the engine receives too much boost at around 3000rpm
Click to expand...
Hi,
Many thanks for the quick & helpful reply, it's much appreciated ... I was pretty sure that it was a "Push" rod from my own observations, but wanted to double-check in case it was some unusual method.

I've tried the same with a small portable compressor at somewhat higher pressure, and even with giving some additional "push" to the rod with a screwdriver against the locknut through the manifold-gap ... but with no joy at all.

As the problem has been ongoing for several weeks whilst I've been trying to diagnose what the problem truly was (I've been chasing potential MAP/MAF faults,etc), I suspect that the wastegate may have seized/rusted more solid during this time.
I also suspect the problem most probably lies at the Manifold end / pivot lever rather than the actual actuator or rod as the actuator seems to be "trying" to push the rod.

As you have stripped your down previously, could you kindly give me a better idea of the layout/design of the wastegate operating mechanism at the manifold, as I can't see or feel the layout behind the turbo itself by eye or touch ... My guess would be that it's basically a simple flap-valve, operated by a (possibly bushed) shaft passing through the cast-iron manifold, which in turn has a simple "lever arm" attaching the shaft to the actuator-rod.

IF my above guess is correct, then I would suspect that the problem could well be that the "shaft" has seized/rusted into the manifold bush/bore that it passes through.
Was that perhaps how yours had seized, or was it something/somewhere else when you got it stripped down?

Much Obliged.
Bob
 
On mine (70000 miles) its the actuator that seized internally the shaft that passes through the turbo was slack through wear.. On the panda I removed the turbo to free it all off .. If it happens again hopefully in the closed and not open position I will fit a pressure release valve in the pipe work to the inlet manifold (they look to be around £25 on flea bay but they are probably a cheaper and easier option (undoing turbo and exhaust tight or seized nuts are a receipe for disaster)
 
notsmartcars said:
.. If it happens again hopefully in the closed and not open position I will fit a pressure release valve in the pipe work to the inlet manifold (they look to be around £25 on flea bay but they are probably a cheaper and easier option (undoing turbo and exhaust tight or seized nuts are a receipe for disaster)
Click to expand...
I certainly get what you mean about potential problems from tight/seized nuts, but I'd personally be wary of simply fitting a pressure release valve into the inlet manifold system, as whilst that might indeed perhaps drop the pressure down to a manageable (Non-ECU tripping) level, it would still mean that the turbo vanes themselves would still be "over-driven" (in terms of turbo-RPM) by the excess exhaust gases passing over the exhaust-side vanes (thereby causing it to spin MUCH faster than needed for a given "manifold boost pressure") ... which would certainly be "bad news" for the long-term longevity of the turbo itself.

When you'd stripped yours down & got it fixed and working again, how much linear travel (roughly) would you say the actuator rod moved from start (gate closed) to end (gate fully open)? ..... 10mm? / 20mm? / ??mm?

Cheers
Bob
 
I do not have any answers, as I think my car is developing the same problem. I used an american OBD reader attached to a laptop to check out the Panda after it lost power during an overtaking manouver, and it came up with the following error codes: P0106 and P0238. I can look at graphs of the various sensors in real time with the OBD teader, and the MAP sensor seems to read ok, with a low reading at idle and increasing with revs, falling back again when the revs drop. The barometric pressure spikes occasionally which is a worry as I think the barometric pressure measurement comes from the ECU? Of course all the pressure readings are in kPa which I am not familiar with. (more of a PSI or mmHg chap!)
From my research (on this forum) the error code P0238 is probably due to a jamming wastegate ( if the MAP and airflow sensors are OK, which they seem to be). My turbo is the KKK KP35. When I looked at the actuator which seems to be some kind of diaphram operated by positive pressure piped from the compressor outlet side of the turbo, I could not get the arm to moove at all. I this right? Does the actuator only move if positive pressure is piped into the diaphram? Or should it be possible to moove it over and back using a screwdriver?
So what are the questions?
1 Should the barometric pressure spike? If not, is that a problem with the ECU?
2 Does the non moving wastegate actuator mean anything? Should I disconnect the little pipe feeding it, and pressurize the diaphram to test it?
If I do what pressure should I use?
3 Is there anything you can do on the car to get a stickey diaphram mooving?
MDH
 
sellickjw said:
Not sure if you've found the real problem to this, but I've already been through two MAP sensors (max air pressure), and two MAF sensors (main air flow), all done at the recommendation of various Fiat Dealers. I've since had Simonstone of Bath tell me they know how to fix it, but that they'll not tell me what they'll do. - I now know why !
The turbo on the Multijet engine is a normal wastegate style turbo, not a variable vane type, and when we took ours off for a look see, the wastegate diaphragm actuator was stuck. We couldn't shift it with a pressure / vacuum tester, but with a little leverage with a pair of pliers it came free easily. - Note that on the car, the diaphragm rod angles upwards as well, which wouldn't help if you managed to get water lying on it.
Now I've got the Panda Multijet back working correctly, no more limp home mode cutting in as you go past 3000 rpm anymore.
Unfortunately you don't get the extra boost sub 3000rpm just before the MAP sensor shouted for help, and limp home mode kicked in. - Yes, not surprisingly, there was definitely more grunt than usual.
My question now is, how does the Electronic chipping of a Multijet give more power, if they do not adjust the wastegate settings ?? - I'd have thought you still needed to get more compressed air into the engine, i.e. higher boost, to go with any extra fuelling from an ECU mod ??
Oddly, the following day a Grande Punto came in with exactly the same problem, so all we did was pull the small rubber waste gate actuator pipe off the front of the inlet side of the turbo, which is easy to get to, and gave it a couple of puffs of compressed airline air pressure, and it freed it up for the guy ASAP.
I'm just wondering how many labour hours the dealer would have charged me for the 10 minutes work it really took <grin>.
Click to expand...


Thanks I had this problem on an 06 car that I recently bought. Yesterday my mechanic friend fixed it using this advice and a code reader the car goes well now.

The actuator was stuck as you suggested.
Well done
Dtgb
 
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