GT TDi Power loss on turbo at 25rpm

[jouleskeys]

Where's my turbo boost gone??

Firstly I am not a mechanic so please make this simple (cheers!!).

When I put my foot down, you can hear the turbo setting in at 20rpm and it pushes, then at around 25 there is a power loss; it just drags down and does not push any further. Even when going around 70, I have found that occasionally it suddenly decides to not rev up any higher than 22, then suddenly kicks in with power again for a couple of notches, then freezes again. It's weird, and I am yet to really enjoy what this car can do as I bought it a couple of months ago.

The car has recently had an oil change and a new petrol filter in hope that these may sort out the issue, however I have no changes as yet to the problem and really wanna get this sorted.

It is a GT TDi (red Di) 1.9 115bhp 2001 (UK: Y reg), it's done 111,000 miles.

Hope someone can shed some light on this and do share the possible cost?? Thanks!

Edited August 17, 2008 by jouleskeys

[cruiser647]

It sounds like your MAF (Mass Air Flow meter) might be knackered.

It sits just behind the airbox, between the airbox exit and the engine covers.

I removed the connecting pipe and sprayed Carb Cleaner in there. Waited for it to dry and then started the car up. Made a big difference.

However, I eventually had to get a new Bosch MAF (£55).

[benjie]

Yes, it's almost definately the MAF. If all your boot had gone, you'd kind of be thrown forward in your seat!

[yangzone]

I've been having a similar problem somewhat frequently with my '03 Golf 1.9 TDI 5-speed.

'Driving along fairly lively and suddenly I lose (some) power - no poke. So I let off the accelerator, depress the clutch, and switch off ignition and back on again right away and let in clutch again and full power is restored. Probably the same sensor? Must find it and try cleaning it?

[cruiser647]

I've been having a similar problem somewhat frequently with my '03 Golf 1.9 TDI 5-speed.

'Driving along fairly lively and suddenly I lose (some) power - no poke. So I let off the accelerator, depress the clutch, and switch off ignition and back on again right away and let in clutch again and full power is restored. Probably the same sensor? Must find it and try cleaning it?

Easy to do! 5 minute job. Use Carb Cleaner from a motor factors and cotton swab gently on the metal sensor.

[benjie]

Mmm.. carb cleaner. Temporary fix at best. Much better to replace.

yangzone - what you're describing may not be the maf sensor. When you say 'fairly lively,' are you takind the revs to 4000rpm? If you are, you may be hitting the rev limiter. Whatever it is, it doesn't sound like a MAF problem to me. Does your car accellerate ok, then at about 2000rpm, loose some power, then the power picks back up at about 3500rpm?

[yangzone]

when I say lively... not racey.. not hitting the rev limiter... a little over 3k at each shift, then when it settles down to about 60 - 70 mph a sudden drag as if turbo disengaged... then no acceleration, just sluggish reluctance to maintain 65 mph on the flat... foot to floor does not increase speed unless on a down gradient... if on an up gradient it edges toward 55 mph with foot to floor. But switching off/on the ignition as I described returns full power... until the next journey.

[Mook]

Have you checked (or had checked) all your turbo boost pipes?

[BW2309]

These engines are very prone to sticking vanes in the Variable Turbine Geometry Turbo. If this is the case then a "maximum boost limit exceeded" fault will be stored in the fault ememory. What happens is that the vanes stick and so removes the turbo's ability to regulate boost. Once the boost reaches a high limit it cuts it out and will not restore it until the ignition has been cycled on and off.

A failed MAF should really make itself known all the time rather than a a lack of boost at a very specifica RPM.

If this is the case then the usual remedy is a new turbo but there is a new thing on the market called Innotec Turbo Clean. This when used properly can clear and lubricate the vanes. I've had pretty good success with it.

Edited September 29, 2008 by BW2309
Spelling mistake

[BW2309]

........Or a boost leak as suggested by MOOK. This would be acompanied by a higher degree of black smoke as then engine can't burn all the fuel being supplied.

[cruiser647]

These engines are very prone to sticking vanes in the Variable Turbine Geometry Turbo. If this is the case then a "maximum boost limit exceeded" fault will be stored in the fault ememory. What happens is that the vanes stick and so removes the turbo's ability to regulate boost. Once the boost reaches a high limit it cuts it out and will not restore it until the ignition has been cycled on and off.

A failed MAF should really make itself known all the time rather than a a lack of boost at a very specifica RPM.

If this is the case then the usual remedy is a new turbo but there is a new thing on the market called Innotec Turbo Clean. This when used properly can clear and lubricate the vanes. I've had pretty good success with it.

This happened to me, but it was the MAF. At a certain RPM (just over 2500), the turbo would stop, so I effectively had a non-turbo car!

On restart, the car would be fine. I never really take the car above 2500 rpm, so avoided the issue. I would clean the MAF and all would be OK for a while until I replaced the MAF. Now I can rev it up to the limiter (not that I do, as there is plenty of boost low down) and the turbo is still there! I still don't go over 2500 on most journeys.

[yangzone]

OK . I should have mentioned the error is 17964 [01/01]

[Rustynuts]

17964 is charge pressure control: negative deviation. Means you're not getting the requested boost. Possible causes are a loose or split boost hose, turbo vanes may be sticking, N75 solenoid valve maybe faulty, for a start.

[yangzone]

Thanks for the ongoing help. It's helping me get my question together for this 03 VW Golf TDI 1.9:

What I'm really asking: does the symptom of the power loss ONLY above 2,800/3,000 revs (when pulling high gears) give rise to the problem being definitly one (or more) particular component failures? Specifically with the error code 17964 (charge pressure control: negative deviation.)

Remembering that I can, while cruising along, right at the time of power loss, switch off and back on the ignition to restore full power... and power loss *usually* will not happen twice on the same journey.

[yangzone]

And no black smoke, just power loss. All else seems ok.

[Rustynuts]

The ECU is a clever piece of kit. It knows what the engine parameters should be at any given time. Therefore, when it asks the turbo to produce x amount of boost, it expects X amount of boost at the manifold absolute pressure sensor (map sensor). If the turbo produces X amount of boost but you have a hole or a split in one of the boost pipes, then X amount of boost doesn't show on the map sensor. What shows is X minus the amount which is lost through the split hose. In this case the actual boost is (let's say) Y. So the ECU sees a lack of boost, but will cope with a small deviation while making minute adjustments to the fuelling to compensate. When the difference between the Required boost [X] and the Actual boost [Y] is greater than a certain value, then the ECU shiuts down the turbo (Limp mode) and you lose all power. Cycling the ignition resets the ECU back to full operation, and you carry on as before. Or until the difference between X and Y is too much for the ECU to cope with.

So, the sudden drop off in power isn't the fault. That's the ECU giving up trying to cope with the fault (lack of boost) and shutting down the turbo. If you can find and fix the fault then the ECU will no longer see a problem and won't go into Limp Mode.

[yangzone]

Thanks for that explanation.

I was wondering if it is likely that the problem could be pinpointed because of the specific conditions. I am driving around very lively in this car. It is accelerating very well. Gets up to good speeds quickly. The performance is great (for this type of car). The economy is good - near 50mpg with my heavy foot.

It's only when pulling load at over 28k that the ecu shuts off the turbo. For instance: a cracked hose... is it poss that the hose would be ok for the rest of the demands and suddenly be unable to supply boost under the above ecu shutoff conditions?

[cruiser647]

It's only when pulling load at over 28k that the ecu shuts off the turbo. For instance: a cracked hose... is it poss that the hose would be ok for the rest of the demands and suddenly be unable to supply boost under the above ecu shutoff conditions?

Yep, the turbo pressure can and does make the hoses expand a bit - enough for a split to manifest itself enough for the ECU to notice.

[yangzone]

So you're saying the turbo pressure would be higher at the point of pulling in 4th uphill at 3-3.5k and not while accelerating hard (same revs) in 3rd to get from say 20 - 50mph (when there's never a problem?) Would the hose not be under the same or more pressure under heavy acceleration in 3rd?

[Rustynuts]

Maybe not higher, but out of required limits for longer which the ecu has more of a problem with. Big differential for a short time, or small differential for a longer time, both will cause a shut down.

[yangzone]

Maybe not higher, but out of required limits for longer which the ecu has more of a problem with. Big differential for a short time, or small differential for a longer time, both will cause a shut down.

I forgot to complete my posts. I did get to the heart of the problem. It was not a split, cracked or a leaking hose - that would have been simple. The hose had degraded and was *collapsing* (under suction) at a particular (cornering) point where it was vibrating against the engine or something attached - anyway: new hose, all good. (So a good looking, uncracked, unsplit hose is not necessarily a functioning hose.)

[Colink]

My problem is identical to that described by Yangzone (over several posts – abbreviated below)

But is my problem likely to be the same vacuum hose? What hose? Or something else?

SUMMARY

VAG-COM shows - 17964 is charge pressure control: negative deviation

Power loss ONLY around 2,800/3,200 rpm (when pulling high gears with load)

2,800/3,200 rpm in lower gears is not a problem.

When problem occurs, switch off ignition and back on restores full power.

I can replicate the problem at any time with the correct conditions.

When driving in close proximity to a wall or hedge, with windows down there does appear to be a sucking sound related to the turbo (Yangzone did not describe this symptom). My hearing is not great so a bit unsure about this.

Yangzone found the problem to be a “collapsing” vacuum hose.

Rustynuts Gave a really good description of what the ECE does if the boost is incorrect and this fits well with Yangzone’s final solution. ie vacuum hose does it’s job when load is low (ie rpm 2,800/3,200 rpm in low gears, on flat is OK, but up hill in higher gears requires more vacuum and collapses.

I am reasonably capable of following instructions and finding faults. I was an auto-electrician many years ago, but I do not have a ramp and am unfamiliar with modern diesels.

I gave the description from Yangzone and Rustynuts to my mechanic, he put the car on the ramp and examined all vacuum pipes but cannot find a problem pipe.

Is there any easy way of testing all the hoses? Can I connect a small compressor or even a bycicle pump to each hose to test it

Some other suggestions in this thread:

Change the MAF – I swaped the MAF from a tdi Fabia, problem still same on Cordoba, no problem on Fabia.

Turbo viens seizing – I doubt this is the case as problem is resolved instantly by turning off and on the ignition. I would assume sticking veins would not clear so easily.

A couple of other factors - in case relevant.

I found that one of the plastic brackets at the top of the air filter was broken causing a poor seal. I think I have fixed this. I realise that poor filter seal would allow a greater air intake, but presumably not any more than removing the filter, which presumably would not cause my symptoms.

I know the EGR can get quite clogged with oil gunge. My mechanic says that there is quite a lot of oil around the turbo. The air pipe that goes from the EGR down to the right inner wing is split slightly (at a joint) about 6 inches from the bottom (ie just below headlight level), some oil is coming out here onto the inner wing.

If this is not the problem I would still appreciate comments on this split and oil.

Thanks ColinK