no power below 2000rpm, bad MPG!

martincloud9 · Feb 25, 2009

Hi,

I have a 2004 Seat Leon TDI 150 PD and These are the problems:

1) Almost no power below 2000 rpm, you can plant the pedal and the car doesn't speed up. After 2000 rpm you have to pull your tongue out of your throat.

2) My MPG has gone from 55 to 37.

I have checked the timing, replaced the injector seals, cleaned the EGR valve, replaced the MAF unit, checked the vacuum hose from the N75 to turbo (no leaks), the vein control arm moves down about 1" then gets alot tougher to move (how far is it supposed to move?), I've plugged it in to VAG and no faults, the vag says the power can't keep up with demand and then shoots up to giving too much, I've changed the air filter, cleaned the MAP sensor and changed the coolant sensor.

Any ideas?

How would you check the turbo pipes for leakage? the engine is too noisy to be sure..

How far does the vein arm go down if it is working properly? I'd rather not take the turbo apart, but I'm gonna do it on the weekend if I can't find an answer.

Does my car even have a N75 valve? (whatever the turbo vein vacuum tube goes to creates a vacuum). And where can you buy one from? Most of the places I have asked are out of stock.

Any help will be much appreciated, thanks.

sssstew · Feb 26, 2009

i would log boost requested vs actual with vag com and see what its doing. if youve replaced the MAF then this should rule it out but its worth while logging that also.

Yes it does have a N75, on the back firewall, two valves one is the N18 EGR Control Valve, the other the N75. Most places wont stock these, you used to be able to get them from vag parts at a good price but they have gone now so your looking at a local dealer for the part really.

But my initial thoughts are a vacuum pipe which is the problem, i had the same sort of issue with my car once where after a service the vacuum pipe to the vacuum reservoir bulb had come off, reconnected it and it was back to normal. So check all your small vac pipes and connections.

martincloud9 · Feb 26, 2009

Cheers mate. You seem to have the same ideas I had. I've logged the requested vs actual. The results show that at first actual can't keep up with demand, then rockets up to more and then levels off about 3500. In some areas actual stayed loads above as well.

I checked the pipes yesterday when I checked the turbo. I sucked on the pipe going to the bulb and it had a good vacuum and made the vein arm move a little.
Not sure how easy the arm is supposed to move, but I could barely do it. The N75 does create a vacuum, not sure if it the right amount. It doesn't seem alot though. I have no frame of reference to know how it is supposed to behave.

Gonna take the turbo apart tomorrow anyway just to knock another thing off the list.

What gaskets will I need?
Also, is it possible to take the turbo apart without removing the manifold? It is rather cramped in there, but it is only 4 bolts....

Thanks

sssstew · Feb 27, 2009

your lucky its not going into limp mode with over boost if it stays above loads like you said.

Anyway, yeah drop the turbo off and clean it up, from what i have read it will need to be manifold off though.

UncleFester · Feb 27, 2009

I'm thinking the vanes might be clogged - how much mileage has it done and how do you generally drive it, looking at your quoted mpg ....... it must be driven quite gently to get that. Have you tried giving it a good run through the gears a few times?

martincloud9 · Feb 27, 2009

Normally the car has been running rather gently. I took it apart today and found that the veins move ok. What is a worry though is the bearings. I have got about .5mm move on them and it has slightly started to buff one side of the housing up. Only slightly, but from what Essex Turbo tell me, if it's going, it ain't gonna get better. Especially in the pocket department too...£380 + VAT!!! Ouch!

I logged the info on VAG last night. It showed a massive demand but poor actual, then it slowly boosted way over the top over the next 1000 rpm, then up and down over the next 1000 rpm and finally settled down.

Would a dodgy bearing cause turbo lag? Would it also cause poor MPG? Would it likely be a cause of unburnt fuel on start up (grey/dark smoke)?

I hope a replacement unit sorts this out. After all the bit's I have checked and replaced, I'm running out of things to change/clean/check!

martincloud9 · Mar 1, 2009

Ok, the car has done 115000 miles. It has had regular services with the correct oil. By regular I mean either 6 months or 6000 miles. It has had to have the cylinder head replaced because the cam wore through a tappet.

What appears to have happened here. The EGR valve clogged up because of it coming on loads whilst 'town' driving. It also clogged up because there is oil coming from the breather pipe, not lots, but enough to turn the soot (from the EGR) in to sludge. I'm guessing that is what was making the glow plugs to keep failing...?
Somewhere along this line (probably the MAF sensor must have ballsed up) as the turbo started over boosting.

The MPG is back up to scratch. The turbo is settled back to normal, although it would be better if it started coming in to effect a little earlier.

Is there any way to get the turbo starting earlier? I.e. getting the veins aligned with a little more trim?

UncleFester · Mar 1, 2009

martincloud9 said:
Ok, the car has done 115000 miles. It has had regular services with the correct oil. By regular I mean either 6 months or 6000 miles. It has had to have the cylinder head replaced because the cam wore through a tappet.

What appears to have happened here. The EGR valve clogged up because of it coming on loads whilst 'town' driving. It also clogged up because there is oil coming from the breather pipe, not lots, but enough to turn the soot (from the EGR) in to sludge. I'm guessing that is what was making the glow plugs to keep failing...?
Somewhere along this line (probably the MAF sensor must have ballsed up) as the turbo started over boosting.

The MPG is back up to scratch. The turbo is settled back to normal, although it would be better if it started coming in to effect a little earlier.

Is there any way to get the turbo starting earlier? I.e. getting the veins aligned with a little more trim?

Remap?

Is it all running ok now? To be honest i'd consider giving it one good run a week .... mine gets a good run every day and the EGR is almost clean inside!

martincloud9 · Mar 1, 2009

Remap? I've had the car about a year now and it has cost me about £4000 (plus the £7000 when I bought it) and 9 weeks with it off the road. I'd love to do it, but I couldn't afford it.

I normally would give a good run, but as it hasn't been running right I wasn't too keen. Plus it has been running rich for a while (37mpg!) Almost like the car was trying to commit suicide....

I am a software programmer and am in the middle of making my own VAG programme. Is there any way I could remap it myself? I know it would be a long path but I would love to give it a go.
Any places to start?

Oh, almost forgot. The car is running great now. Great throttle response, smoother turbo boost and much better fuel economy. All in all, a thumbs up.
I would suggest for anyone to not bother going to a garage unless they really have to. I have spent lots of money getting nowhere with them. Just roll up your sleeves, don't let these modern engine intimidate you (they're still the same b****x underneath) , use a this site and take your time.

NI3K · Aug 3, 2010

what eventually sorted the smoke on startup and no power below 2k?

Muttley · Aug 3, 2010

martincloud9 wrote

What appears to have happened here. The EGR valve clogged up because of it coming on loads whilst 'town' driving. It also clogged up because there is oil coming from the breather pipe, not lots, but enough to turn the soot (from the EGR) in to sludge. I'm guessing that is what was making the glow plugs to keep failing...?

The EGR valve is prone to clog, and the inlet manifold to coke up too, because the hot sooty exhaust gas from the EGR meets the oily inlet charge (oil mist from the crankcase breather is normal) to form a nasty sludge which bakes on and slowly gets thicker.

Eventually the EGR valve starts to stick becuase of the buildup of crud. The low-rev issue could be from the valve never closing properly, letting some boost out. Overboost at the top end is again likely due to the valve not shutting properly, only now the exhaust pressure is higher thant the inlet and give overboost.

I doubt it has anything to do with the glowplugs, which are in the cylinders.

I guess you've cleaned the EGR valve up which has cured your problem (you don't say what you actually did). I hope you cleaned out the inlet manifold as well, as it will have been choked by the buildup of crud.

Somewhere along this line (probably the MAF sensor must have ballsed up) as the turbo started over boosting.

More likely stuck EGR

The MPG is back up to scratch. The turbo is settled back to normal, although it would be better if it started coming in to effect a little earlier.

Earlier than what? Below, say, 1700 rpm there isn't enough exhaust gas to spin the turbo fast enough to give full boost, even with the variable geometry turbine inlet vanes.

Is there any way to get the turbo starting earlier? I.e. getting the veins aligned with a little more trim?

At low revs the vanes are at minimum opening. This gives maximum back pressure, but crucially gets the gas speed up (smaller turbo inlet = faster gas flow) and it is the speed of the gas that is critical in getting the turbo spun up.

Trying to extend this lower in the rev band doesn't pay back as there isn't enough boost available to counter the rise in back pressure.

drozia · Apr 5, 2016

It is almost caused by curropted vac lines and hoses. Dont waste your time. Check them first of all. It is the cheapest method.

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Bigjohn84 · Apr 5, 2016

Mate this was 5 years ago lol the dates at the top left of the thread lol

Thai-wronghorse · Apr 5, 2016

Haha

Sent from my HTC One_M8 using Tapatalk

drozia · Apr 6, 2016

Is it a problem for answering a subject which is almost actual also today...

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Bigjohn84 · Apr 6, 2016

Well yeh, because people don't search for answers they starts a new thread, happens all the time, don't worry we have all done it when just searching through the forum

drozia · Apr 6, 2016

For example I suffered from my 2003 toledo 1.9 ASV engine and when I searched this forum i benefit from some subjects and get the solution

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no power below 2000rpm, bad MPG!

martincloud9

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sssstew

Editing your spelling

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sssstew

Editing your spelling

UncleFester

Grumpier by the day!

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Grumpier by the day!

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Muttley

Catch that diesel!

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