misfire!!!!

[leobiza]

Hi all,

Can anyone help?

I have an x reg leon cupra 1.8 20vt with an AUQ engine, I have been experiencing an intermitant misfire accompanied by very uneven idle for a few weeks now. It will be fine on one journey then for no apparent reason on the next the misfire will start. Give it a bit beans and all is well again for a while, but the problem will keep coming back on the same journey.

Next time I drive the car its as good as gold!!

Today whilst driving to Taunton I dropped it down to overtake, plently of power, no misfire, as i slowed up it started to misfire badly.

I got home and it seemed to have cleared, went out half an hour later and everthing was fine and then on the way home the engine warning light came on and the engine now idles as rough as badgers *** and misfires all the time. At idle there is a bad knocking which stops when I rev it.

As it is the weekend I have not contacted the dealer yet, and wondered if anyone could shed some light as I fear it could be expensive to sort it.

Many thanks in advance,

Matt

P.S its done 148000 miles with full fssh

 

[cordobabrendy]

lambda sensor maybe, i had a similar issue.

 

[leobiza]

Thanks for the advice mate, i'll look into it.

any other ideas would be much appreciated.

Matt

 

[leobiza]

I've been searching through other posts on the site, it seems like the problem is either the temp sensor or the lambda, can any let me know where these are located as i'm tempted to tackle the job myself when I have had the fault codes read.

Matt

 

[cordobabrendy]

lambda sensors (2 of) are on the cat, under the car you wont miss them, the wiring to them should have heat wrap on them.

 

[CupraUK]

I know it may sound a bit basic, but could be a coil pack that has not completely failed and it just playing up.

 

[cordobabrendy]

vagcom will tell once he gets it onto the case!

 

[h100vw]

So Matt did you fix this one yet. I had a similar thing on my Cupra. Number 4 coilpack died one morning on the way to work. No hints it was going, it just quit.

Idle was really rough, the knocking smoothed out a bit with revs if the car was at a standstill but the misfire was very bad under load.

Gavin

 

[leobiza]

Hi Gavin,

yeah it went into my local auto electrical place today, two fault codes logged.
one saying the brake lights were out due to a faulty pedal switch and the running problems were caused by a faulty valve in a breather pipe that goes from the turbo to the air inlet tube, sorry but I don't know what it does or what its called, but it is now running as smooth as silk.

cost me £170.00 in total ouch!!!!!!! wish i'd done it myself now as the brake light switch and valve only came to £30.00

Matt

 

[leobiza]

The part number for the valve is 06A145710N, anyone recognise it as I would like to know what it does/is.

 

[leobiza]

Got it now, N75 valve, which I believe is bascally the dump valve.
correct me if I am wrong.

 

[CupraUK]

170 quid for a N75 valve??? They are 30 quid from the Stealers!

Its not the dump valve, its a solenoid valve that controls boost. Cheap part, 2 minutes to fit.

 

[cordobabrendy]

its a boost solenoid that triggers to release excess boost via the wastegate, its doesnt vent the excess itself though so its not a dump valve.
have a read below
http://s2central.net/ds_N75.html

 

[leobiza]

tell me about it, the N75 cost £20 + vat, the labour charge was the sting in the tail. they had the car all day diagnosing and also changed the brake light switch.
could have probably done it myself in 10 mins.

 

[cordobabrendy]

n75 switch is a 2 min job with the engine off, palastic engine cover off, locate the n75 on the passenger side and whip it out, with a bit of persuasion the standard clips can be left on the pipes unharmed then slide the rep valve back in, cover on , check engine runs fine down the road and job done.

 

[CupraUK]

£495 buys you 2 years RAC gold warranty, all of a sudden it sounds like great value for money!

 

[leobiza]

sounds like a good idea, especially with 147000 on the clock.

thanks for all your help and advice guys.


Matt

 

[leobiza]

I think I am wrong with the N75, looks more like the throttle bypass valve as there are no electrical connections.
as shown here http://www.s4biturbo.com/art-dvtests.php

Matt

 

[CupraUK]

Thats the dump valve (or recirculation valve as 18t s don't dump to the atmosphere).

Its common for the Bosch ones to fail as they have plastic diaphrams that split. Many people here change for the Forge 007P which is a metal piston with a lifetime guarantee.

Still a 5 minute job to change.