Hi folks. Just posting this to see if anyone has any ideas on my car. Recently started not running or boosting properly intermitantly. At times its very sluggage then all of sudden boosts, and when it does it at worse its sluggage then kinda backfires and off she goes. Another symptom is when at a steady speed and turbo cums in its almost like you feel ut spooling up then backs off/hesitates as if not full throttle. Cupla fault codes but the lamda 1 has always been ther and never effected runing wise. Other 2 are

17704 error in mapped cooling system.

17705 presure drop between turbo and throttle valve.

 

I have tryd mass air flow meter as i was told by vw mechanic it could be that but still same. Changed fuel filter. Made sure fuel pump wasnt clogged up with crap. Its realy doing my head in as when it does run and boost good its a quick car as its stage 1 with decat downpipe. Mibi also worth mentioning its got boost guage and when it does hesitate/drop power the boost stayes the same so turbo it spooling up. Any input much apreciated guys 

@richbogle

 

17704 - Never seen that one before. If you're using VCDS use it to read the reported engine temperature values off the EMS channel rather than assuming that a steady temperature gauge means a steady temperature value.

 

17705 - This makes me think of a boost leak. The gauge might be a red herring because it will report boost where it's connected and not across the whole intake pipe run from the turbo. Check the pipework, and particularly the joints.

I did think boost leak myself but everything looks ok. And it does boost realy well (when it does go well) 1 min its hesitating spluttering and farting then next min its going like a rocket

Check the wiring connector to the N75 for abraided wiring or connectoe damage.

 

Some more info for you - http://wiki.ross-tech.com/wiki/index.php/17704/P1296/004758

 

Does your temp gauge read 90 all the time, or does it drop coasting down slopes or cruising for a period of time.

 

http://wiki.ross-tech.com/wiki/index.php/17705/P1297/004759 

 

This one can be full of blind alleys, what age is your car and rough mileage, as many have had this including myself at some point - in my case it was a dirty throttle body.

 

As Ken said check your pipes and the simple stuff first, most of our cars are 12-15 years old now, so pipes will be hardenning and failing quite regular now just due to plain old age.

 

 

Edited 11 October, 20178 yr by kentphil1

Thanx for the help mate. car is a 03 plate and got 160k on clock! I know its high miles for petrol but apart from this fault car is in prity mint condition. 

Temp guage doesnt read 90 unless its sitting about its usualy alot lower than that, posibly a thermostate jamed open didnt think this would cause this. Also i have cleaned  out throttle body and calibrated it with our Snap-on machine. Whare is the N75 valve on car? And is the N249 valve just the recuirculating valve? (Dump valve)

sounds like you definately have a coolant temp issue there, how old is your coolant temp sensor, is it a green one or an old black job?.

 

If the sensor is recent, then I would change your thermostat, as undercooling will send all sorts of innacurate readings to the ecu and mess with your fuelling.

 

N75 is located up near the diverter valve just by the bulge in the plastic engine cover - top right as you look into the engine bay standing in front of the car. This random google piccie may help - https://www.google.co.uk/search?q=octavia+1.8t+n75+valve&client=firefox-b-ab&tbm=isch&tbs=rimg:CUo6PDnuzyVLIjjWXqWZ3t7MLkyWTXySVObGjZvRHh0MxrugP8kUQup9pBb_1tSgMTxPWewUppHsuj7uul-_1kldbP1CoSCdZepZne3swuEaJQWbMvqUkMKhIJTJZNfJJU5sYRZYoTYNYkDRwqEgmNm9EeHQzGuxFyGqCevkIBiCoSCaA_1yRRC6n2kEaXHlJZIVZUrKhIJFv-1KAxPE9YRa0Uv8TqlRBAqEgl7BSmkey6PuxGasQAtvnEaQCoSCa6X7-SV1s_1UEYsmg0NoY239&tbo=u&sa=X&ved=0ahUKEwjRyZjnkvPWAhUSJ1AKHTYHBSwQ9C8IHw&biw=1366&bih=659&dpr=1#imgdii=1l6lmd7ezC5gNM:&imgrc=Sjo8Oe7PJUu8hM:

 

The N249 lives under the plate by the dipstick under the small engine cover there. It controls overboosts to the engine/diverter valve, rather being the diverter valve itself, that is up near the n75.

God knows how old the sensor is! I will go out n look just shortly. Thanx again for the info i have a thermostate ther so al change that anyway. What colour of sensor should be on the car? 

Old ones were black, later ones are green. The rule of thumb on these is buy oem or Bossh, anything else won't last long, some on here havn't even outlasted the day.

 

Thermostat is a doddle to do tf you have a 1/4 drive wobble bar set and a remote hose clip compressor for the spring hose clips.

And mibi worth mentioning i popd up 2 the work 2day amd put computer on it again. In the live data it says the coolant temp was 167f which converts to 75 degrees. The guage at that time was reading 90ish

I know thermostate was tricky! Thats why its been in my toolbox for bout a year lol

The sensor is a dual function unit, one part gives a ecu reading, the other part feeds the gauge. It is not impossible the ecu side has gone home for the distant future. A sensor oem was about £30 when i bought mine earlier this year.

 

Stat change is fairly straightforward if you take your time, use reasonable quality 1/4 drive stuff and one of these unless someone has already changed the hose clips for jubilee type clips - http://www.ebay.co.uk/itm/Sealey-Flexible-Remote-Ratchet-Action-Hose-Clip-Clamp-Remover-Long-Reach-VS1663-/141558319690?hash=item20f5888a4a 

the ad is a random one just to show what I mean, rather than a recommendation.

Got the stuff there to do the job. I will get my finger out and report back