GT TDi Power loss on turbo at 25rpm - Page 2

cruiser647 · 02-10-2008, 09:52 AM

Quote:

Originally Posted by 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.

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 · 04-10-2008, 03:42 PM

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

Rustynuts · 04-10-2008, 05:04 PM

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 · 06-10-2008, 10:22 AM

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 · 06-10-2008, 10:30 AM

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

Rustynuts · 06-10-2008, 09:20 PM

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 · 09-10-2008, 10:58 AM

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 · 09-10-2008, 12:36 PM

Quote:

Originally Posted by yangzone

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 · 10-10-2008, 03:37 PM

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 · 10-10-2008, 03:50 PM

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.

04-10-2008, 05:04 PM	#13 (permalink)
Rustynuts Porsche Carrera 4S Join Date: Aug 2004 Posts: 6,707	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. __________________ I only accept pm's from my contacts. If your name's not on the list then you ain't invited.

06-10-2008, 09:20 PM	#16 (permalink)
Rustynuts Porsche Carrera 4S Join Date: Aug 2004 Posts: 6,707	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. __________________ I only accept pm's from my contacts. If your name's not on the list then you ain't invited.

10-10-2008, 03:50 PM	#20 (permalink)
Rustynuts Porsche Carrera 4S Join Date: Aug 2004 Posts: 6,707	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 only accept pm's from my contacts. If your name's not on the list then you ain't invited.

04-10-2008, 03:42 PM	#12 (permalink)
yangzone stranger Join Date: Sep 2008 Posts: 7	OK . I should have mentioned the error is 17964 [01/01]

06-10-2008, 10:22 AM	#14 (permalink)
yangzone stranger Join Date: Sep 2008 Posts: 7	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.

06-10-2008, 10:30 AM	#15 (permalink)
yangzone stranger Join Date: Sep 2008 Posts: 7	And no black smoke, just power loss. All else seems ok.

09-10-2008, 10:58 AM	#17 (permalink)
yangzone stranger Join Date: Sep 2008 Posts: 7	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?

10-10-2008, 03:37 PM	#19 (permalink)
yangzone stranger Join Date: Sep 2008 Posts: 7	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?