Turbo Charger Loss Of Boost

[Fornelo]

Hi My 57 plate S-Max 2.0 TDci has started to develop a fault where the boost of the turbo is completely gone.

This happens ramdomly, but lately I am noticing it comes often on hills, the message on the dashboard is "Engine mulfunction", and the traction control light is also on.

As soon as the car is turned off and back on the car returns to full operating mode, with no issues, until the fault re-occurs, which could be next day or two weeks later.

I have been told different things by different garages, from ( Mmmmm, you need a new turbo, too it is probably the air pressure sensor).

The message on the diagnostic computer said " Turbocharger/Supercharger Boost control A position exceeded learning limit ".

Any ideas??.

I do not want to change the turbo if the turbo isn't the problem.

I have changed the actuator sendor with no luck too.

Many thanks in advance.

[mick85]

If it intermitting sounds electrical sensor or wiring have u checked anything yet

Sent from my iPhone using Ford OC

[marine-engineer]

Hi

I had the same problem on my 2.2 Tdci 2008, check the hose that goes from intercooler to the air intake valve, if there is a leak you will have that problem. The turbo pressure will leak out, and not give the engine completely air pressure.

Regards from Norway

[marine-engineer]

Part marked with red on the 2.2 TdCi

[Fornelo]

Hi,

I have tried the actuator sensor and I am trying the MAP sensor this weekend.

I am also thinking of using Turbo cleaner for the sticky vanes someone mentioned before.

I will check for leaks also.

Wish me luck. :D

[marine-engineer]

Yeah, I was doing the exact same myself, I changed the MAP sensor IAT sensor and fuelfilter before i checked the hose. If there is a leak it would probably be some black dirt around the place too.

[mikeywalker1967]

My fiesta was doing the same thing and it was the Egr valve sticking which was putting it in to limp mode.

Sent from my GT-I9300 using Ford OC mobile app

[GalaxyGhia]

My Galaxy 2.0 tdci 2008 has just been through this problem with the turbo. I had "boost control a position exceeded....", "turbo / supercharger boost system performance", ABS and body control module faults.

The ABS and body control rely on the engine BCM, so if its faulty the ABS etc will also display faults.

I used ForScan and an ELM327 OBD to help diagnose the problem. Software free £15 for quality ELM327.

Basically the turbo vanes were sticking. I removed the turbo on my drive, stripped it down, cleaned it, reassembled and refitted it.

Basic tools needed and can be done in a weekend.

Garage costs would have been £350 for recon turbo + labour. Probably cost £500 - £600

Ford new turbo £950 + labour.

If anyone needs more info let me know.

[GalaxyGhia]

My fault used to occur mostly on hills to start with. Very randomly. It will eventually get worse.

I think if the engine BCM detects an overboost for more than 5 seconds it goes into limp mode.

Diesel fuel additive/cleaner did help for a month or two, but eventually it was happening several times a day.

Since fixing the turbo the MPG has gone from 37 to nearly 41mpg around town.

[FOCA]

My Galaxy 2.0 tdci 2008 has just been through this problem with the turbo. I had "boost control a position exceeded....", "turbo / supercharger boost system performance", ABS and body control module faults.

The ABS and body control rely on the engine BCM, so if its faulty the ABS etc will also display faults.

I used ForScan and an ELM327 OBD to help diagnose the problem. Software free £15 for quality ELM327.

Basically the turbo vanes were sticking. I removed the turbo on my drive, stripped it down, cleaned it, reassembled and refitted it.

Basic tools needed and can be done in a weekend.

Garage costs would have been £350 for recon turbo + labour. Probably cost £500 - £600

Ford new turbo £950 + labour.

If anyone needs more info let me know.

You are correct - the sensor would not detect exessive boost if the hoses were leaking

and it would be foolish to assume the sensor is faulty because it is reading exessive boost - it may be that the sensor is working as it should and there is exessive boost at the sensor (usually before the manifold)

What happens is the carbon builds up in the VNT/ variable vane mech over time, cars that are driven sedately or engines that produce exessive smoke tend to have more of a problem (sometimes a good "italian tune up"- does the world of good) because the VNT mech is not used so much in its full travel - the VNT mech controls the boost pressure (along with the actuator, from the ECU)

under hard acceleration or uphills, the engine is under heavier load/ wider throttle, so more boost is required, with the boost control systems not operating correctly (with the VNT sticking) the boost can increase untill it gets very high, this is when the MAP (manifold absolute pressure) sensor detects this exessive boost and puts the system into limp (home) mode to protect the engine from damage - if the car is driven slowly/ light load, (eg, around town on the flat) this may not happen as the boost level may not rise high enough to trigger limp mode

A sticking VNT can also damage the actuator

I agree that a proper strip down and clean out of the VNT vanes is the way to go and the "super-dooper spray etc" is of limited use and a temporary solution at best

A good clean out of the inlet manifold (of the carbon / gunge the EGR valve has deposited) helps, and frequent air filter changes (so it does not run too rich that can increase the amount of carbon in the VNT mech)

Dare i say it - fitting a solid EGR blanking plate can help reduce soot (the VNT comes before the DPF (if fitted), so there may be carbon/ soot being produce that can choke up the VNT that you don't see)

[GalaxyGhia]

Care needs to be taken with EGR blanking plates. Some engine ECU's will detect the lack of flow.

I believe some fords have a temperature sensor in the exhaust. If it doesn't detect a drop in exhaust temperature from the EGR working then you will get a fault. The EGR valve lets exhaust gasses back into the inlet manifold which cause a cooler burn and reduce the NOx emissions.

You can check a sticking VNT quite easily with a vacuum pump and a rule.

If you apply 0.350Bar vacuum to the actuator the actuator rod should move 9-11mm. On the Galaxy you can do it from under the car with it jacked up or on ramps.

Best thing for modern diesels is to have a small engine and thrash it. With EGR, VNT, and DPF its the only way to keep them clean.

Kind of defeats the idea of getting as much MPG as possible by careful driving.

[FOCA]

Care needs to be taken with EGR blanking plates. Some engine ECU's will detect the lack of flow.

I believe some fords have a temperature sensor in the exhaust. If it doesn't detect a drop in exhaust temperature from the EGR working then you will get a fault. The EGR valve lets exhaust gasses back into the inlet manifold which cause a cooler burn and reduce the NOx emissions.

You can check a sticking VNT quite easily with a vacuum pump and a rule.

If you apply 0.350Bar vacuum to the actuator the actuator rod should move 9-11mm. On the Galaxy you can do it from under the car with it jacked up or on ramps.

Best thing for modern diesels is to have a small engine and thrash it. With EGR, VNT, and DPF its the only way to keep them clean.

Kind of defeats the idea of getting as much MPG as possible by careful driving.

The temprature drop is insignificant, only happens when the EGR is open (a very small percentage of the time) the temprature sensor in the exhaust (if fitted) is not for that reason and cannot detect small changes in the exhaust quickly enough its only there to detect exessive EGTs (not to detect slight drops in the exhauet temp) - + the only reason temps drop when the EGR valve opens is because the oxegen going into the combustion chamber is reduced - less oxegen = less heat = less nox = less power

Effectively when the EGR valve is open it is cutting power and thats the only reason it reduces temps/ nox, you could say turning off the ignition does the same thing

Overall the EGR often has a detrimental long term effect on the car/ enviroment/ MPG

I have 8+ years of research, development, and 1st hand/ hands on practical experience of EGR deletes/ plates etc - and there is a lot of BS floating about on the net about the subject - often spread by people that have never fitted an EGR plate

[GalaxyGhia]

I blanked the EGR on a 52 plate mondeo 2.0tdci because it was sticking open and causing starting problems. That was at 50k miles. Sold the car with 150k miles on. Engine was still going well, no problems. So on older cars it isn't a problem.

I see a lot of blanking plates on fleabay with small holes in to restrict the EGR flow, supposedly to stop an EGR fault.

How would a modern diesel detect a blanked off EGR? I've read on other forums that some people have had to have the EGR function mapped out of the engine management because it can detect the blanking plate.

When should the EGR be open?

I want to blank mine off to help keep the turbo clean.

[FOCA]

I blanked the EGR on a 52 plate mondeo 2.0tdci because it was sticking open and causing starting problems. That was at 50k miles. Sold the car with 150k miles on. Engine was still going well, no problems. So on older cars it isn't a problem.

I see a lot of blanking plates on fleabay with small holes in to restrict the EGR flow, supposedly to stop an EGR fault.

How would a modern diesel detect a blanked off EGR? I've read on other forums that some people have had to have the EGR function mapped out of the engine management because it can detect the blanking plate.

When should the EGR be open?

I want to blank mine off to help keep the turbo clean.

When the EGR valve opens depends on the exact engine/ design - in general it is at lower revs, at part - throttle and on the over-run, if you "boot" it the EGR shuts - this makes a nonsense of the people that think the EGR cools the combustion chamber (because the read it on wiki/ google) because on full throttle/ high load/ revs the EGR is closed, you can often tell when the EGR valve opens because thats when you get the hesitation/ lag/ flat spots - it can also make a "missing" noise ike the exhaust is blowng in one cylinder (in a way, it is) - the EGR may also open on the over-run/ when you lift off the throttle

Generally, you can fit a solid blanking plate on a Euro3 Ford with no issues/ problems, With some Euro4 Fords a solid plate can be fitted and the EML (engine management light) does not come on (no problems) (eg- there have been quite a few euro4 Focus owners that have fitted a solid EGR blanking plate and have not had the EML come on) in general, they have reported less flat spots, better pick-up/ less lag, a smoother engine and slightly better performance, (especially from low revs) some have reported less MPG - this may be because of the extra performance, or the EGR filling the cylinders on the over-run (in the short term)

In the long term the inlet/ inlet manifold being contaminated with carbon (and this carbon mixing with the oil spray from the crancase breather and forming an oily goo) is not going to help the long term MPG as the inlet gets filled up with gunge

A blanking plate with a hole does not stop the gasses/ contaminents, the EGR valve/ system must be working correctly, and the EML may come on anyway because of the reduction in flow - often bigger or more holes need to be drilled to stop the EML coming on - untill its almost if a plate was not there at all - so in many cases you may have not bothered fitting a (holed) plate at all - mostly, of limited use at best and a total waste of time and you may as well not have bothered fitting one

A solid plate completely blocks the exhaust fumes and carbon from the exhaust does not get past it to contaminate the inlet/ manifold or cause flatspots etc or loss of turbo pressure on the exhaust side, if the EGR valve/system is faulty, a solid plate "fixes" it - by effectively disabling the EGR. With a soiid plate fitted, reliability is improved,as if the EGR valve sticks, it makes no difference, on some cars, the EGR valve is expensive, some Euro4 Mondeo owners went through 4 valves in the time they had the car ("120-£200 each) - a solid plate would have prevented that

If you have a PSA engine it may respond differently from a purely Ford designed engine, a Euro 4 / 5 can still have a blanking plate fitted, but the EML may come on, sooner or later (due to lack of flow), there is unlikely to be other issues, and the EML can be reset with a code reader, or the EML could be left on (this may "mask" other faults unconnected with the EGR arising) - some owners chose to run their cars like this anyway with a solid plate fitted, because of the advantages of the plate

If you choose to clean out your inlet manifold (removed and cleaned properly- no "quick fixes"/" wonderspray") at the same time as fitting the solid plate, the inlet will not get contaminated with carbon, you can also clean out the intercooler and fit a breather catch tank - this will keep the inlet/ air intake clean

With that done the car should run smoother, less flat spots, /lag, better throttle response, better long time reliability as less smoke/ carbon contaminates your VNT, (and longer between rebuilds) the DPF should last longer/ take longer to become contaminated- the inlet manifold will not get filled with carbon, reducing MPG/ performance/ making the engine run rich further contaminating the VNT/ DPF - the inlet manifold will never have to be cleaned again (due to carbon build up) or the EGR valve cleaned/ replaced again - with a solid EGR valve fitted

[Welsh Wom@n Driver]

Hi,
This maybe helpful?
I have a 2007 Galaxy Ghia TDCI.

Back in August 2013 (or there abouts) my car starting suffering with Turbo Faults, constantly. I would be driving down the motorway and the car would automatically apply the breaks and go into limp mode. This also occurred while going up hills.

Anyway, took my car to my local garage who advised it was the sensor. (Cant recall the name of the sensor , sorry) Anyway, i paid £160 for a new sensor and drove off a happy person.

Within 2 days i was again in limp mode. Back to the garage i went. They couldn't find the fault and referred me to a garage who specialised in diesels.

The Diesel garage run the diagnostics and said he would check for leaks. There were none.

He then advised i needed a new Turbo BUT he was willing to try something first. TURBO cleaner?

Ok, so Turbo cleaner cost me £100 . (He did this for me) He advised this had worked for some of the diesel taxis he had worked on.

I drove off and two days later i was back to square one - In limp mode.

However, this was the LAST time. It never went into limp mode again. The TURBO CLEANER WORKED.

It is now 2015 and my car has not gone into Limp Mode with this fault since.

I am only posting this as it maybe helpful for someone else. Thanks x

[Victor_98]

Hi guys! I have the same problem on an mk4 Mondeo 2.0tdci 140hp. It says "Turbocharger/Supercharger Boost control A position exceeded learning limit". I cleaned up the turbo but the problem is still on. I also changed the two brown/orange vacuum valves that control the boost and the limp mode persist :( .  What can i do more ?