Hi guys,

Hope someone on here can point me in the right direction, after searching the forum am still not able to find a similar issue.

The wife's octavia started to loose power a few months ago. No smoke and the engine seems to be fine when running normally.

When you go to accelerate, the car is fine up until about 40 mph on the straight or a little less on a hill, then it just seems that someone has whipped out all

the horses in the engine, and just left one that should be e/r to the knackers yard. It just has no power at all. If your on a straight road, it will speed up to 80mph without too much of a strain but as soon as you come to an incline, it dies away again. It's not safe to overtake though.

There is no smoke, the turbo booster pipe seems ok - its had a full service and all the necessaries done. There does seem to be a lot of air you can see in the 'clear' section of the fuel pipe

from the diesel filter, especially when you push the acelerator - not sure if this is the cause and if it is what could cause it.

Took it to my local garage and they said it was the engine management system which I think is a stab in the dark and they dont know the cause. I have had no warning lights on at all.

Anyone have any ideas?

thanks Dy.

There are number of things, which I'll cover quickly.

1. get the car scanned for fault codes and report back if you have any... Just for reference I have never had the engine management light on - even for all the faults described below.

2. MAF. Unplug it and take the car for a drive, if the car is more lively then the chances are the MAF is knackered, or on its way out. It is possible to clean them, but probably only for short term gains

3. Faulty n75 valve. Not very easy to test, about £25 from a dealer.

4. Faulty CTS (Coolant Temp sensor). It has 2 circuits - one for the gauge on the dash and one for the ECU. The ECU side sometimes fails. Again about £25 from a dealer (don't forget to get an o-ring as well)

5. Sticky vanes in the turbo. Pull off the vacuum hose from the n75 valve and suck on it with your hand on the back of the turbo (do this when the engine is cold), you should feel plenty of travel, if not that the vanes are probably stuck. Solution is a new turbo (expensive), or to pop the old turbo off and clean up the vanes. Essentially the vanes get sooted up and then jam, causing an overboost and the car goes into limp mode. Cycling the ignition clears the limp-mode, until it next happens. Mine does this several times a day at the moment, but I am busy working on the house, so I just have to remember not to overtake too many cars, as it always seems to "limp" mid-overtake. :S

In all honesty, I expect it is your (2) or (4). I am guessing yours is a 110, or a later 90 with VVT (early 90s did not have VVT and thus won't suffer from point 5).

Pic to help locate things:

Mbanes is spot on. Strangely a dead or dying MAF doesn't seem to throw a fault code unless there's wiring fault!

Also faults 2, 4 and 5 are unlikely to cause any lights to come on either even if there is a fault recorded.

There are number of things, which I'll cover quickly.

1. get the car scanned for fault codes and report back if you have any... Just for reference I have never had the engine management light on - even for all the faults described below.

2. MAF. Unplug it and take the car for a drive, if the car is more lively then the chances are the MAF is knackered, or on its way out. It is possible to clean them, but probably only for short term gains

3. Faulty n75 valve. Not very easy to test, about £25 from a dealer.

4. Faulty CTS (Coolant Temp sensor). It has 2 circuits - one for the gauge on the dash and one for the ECU. The ECU side sometimes fails. Again about £25 from a dealer (don't forget to get an o-ring as well)

5. Sticky vanes in the turbo. Pull off the vacuum hose from the n75 valve and suck on it with your hand on the back of the turbo (do this when the engine is cold), you should feel plenty of travel, if not that the vanes are probably stuck. Solution is a new turbo (expensive), or to pop the old turbo off and clean up the vanes. Essentially the vanes get sooted up and then jam, causing an overboost and the car goes into limp mode. Cycling the ignition clears the limp-mode, until it next happens. Mine does this several times a day at the moment, but I am busy working on the house, so I just have to remember not to overtake too many cars, as it always seems to "limp" mid-overtake. :S

In all honesty, I expect it is your (2) or (4). I am guessing yours is a 110, or a later 90 with VVT (early 90s did not have VVT and thus won't suffer from point 5).

Pic to help locate things:

Thank you very much for all this advise. Have checked it this morning, unplugged the MAF and it sorted the problem straight away! Many Thanks again for the info.

Thank you very much for all this advise. Have checked it this morning, unplugged the MAF and it sorted the problem straight away! Many Thanks again for the info.

Superb, glad twe could help. You should be able to get a new MAF from the dealers, or a Bosch one from ebay (avoid cheapo ones).

I have had a similar problem in the past which turned out to be the turbo vanes stuck open therefore overboosting, but this last week its been general lack of power, like you don't have a turbo at all. This one seemed to have been the thin vacuum pipe which had chafed through, this is the first one in line from the vacuum pump (on the end of the camshaft) to the white t piece on the bulkhead. I just cut it a bit shorter and refitted, now back to normal. Sometimes the simplest things cause the most annoyance!!