Hi,

My 2002 Octavia (1.6 petrol) failed the emmissions part of NCT as they couldn't get it to stay at 2000rpm when idle. When the engine is cold it will idle at 2000rpm, but once it heats up, then once you try to rev it above 1500rpm it hunts up to around 4000rpm and if you ease off on the accelerator at all, it falls right back to about 800rpm.

I tried cleaning the coolant temperature sensor and tbe throttle control body, but this made no difference.

When there is a load on the engine it runs fine and the throttle control is fine.

Any suggestions as to possible causes would be much appreciated.

Thanks,

Try re-setting the ECU, switch everything off, disconnect the battery for 30 minutes, then without touching the clutch and brake pedals, start up and let idle for 30 minutes, this will re-set the ECU.

 

DB

Try re-setting the ECU, switch everything off, disconnect the battery for 30 minutes, then without touching the clutch and brake pedals, start up and let idle for 30 minutes, this will re-set the ECU.

 

DB

Hi,

I tried that yesterday and again today, but with no effect.

Have you tried the MkI Octavia forum? This is Fabia MkI section

Have you tried the MkI Octavia forum? This is Fabia MkI section

I mistakenly posted to the Fabia Mk1 section,( Newbie), and was unsure how to move the post, so I also posted it in the Octavia section after I spotted this.

I mistakenly posted to the Fabia Mk1 section,( Newbie), and was unsure how to move the post, so I also posted it in the Octavia section after I spotted this.

 

No probs and welcome to Briskoda. Sure you'll get some help pretty soon and good luck

I'm not familiar with the 1.6 petrol, but welcome along (i know its bad news, but....) its nice to see more people mentioning NCTs instead of MOTs

 

try disconnecting the MAF? i seem to recall a dodgy MAF sensor can cause idle hunting on the 1.8T, one would imagine it to be the same on 1.6?

If it runs better with it off, thats yer problem. if its the same, then its elsewhere. 

 

edit - spelling..

Edited 23 February, 201511 yr by mac11irl

I'm not familiar with the 1.6 petrol, but welcome along (i know its bad news, but....) its nice to see more people mentioning NCTs instead of MOTs

 

try disconnecting the MAF? i seem to recall a dodgy MAF sensor can cause idle hunting on the 1.8T, one would imagine it to be the same on 1.6?

If it runs better with it off, thats yer problem. if its the same, then its elsewhere. 

 

edit - spelling..

Thanks for the suggestion.

 

I had the MAF off yesterday and cleaned it, which didn't make any difference, but I didn't try disconnecting it.

 

I will give it a go and let you know if it works.

I'm not familiar with the 1.6 petrol, but welcome along (i know its bad news, but....) its nice to see more people mentioning NCTs instead of MOTs

 

try disconnecting the MAF? i seem to recall a dodgy MAF sensor can cause idle hunting on the 1.8T, one would imagine it to be the same on 1.6?

If it runs better with it off, thats yer problem. if its the same, then its elsewhere. 

 

edit - spelling..

Mac11irl, you may have saved me a lot of money and head scratching.

I tried what you suggested, disconnecting the MAF, and no more idle hunting, then when I plugged it back in again the problem reappeared.

I might try giving it another clean, just in case but at this point I would be happy enough if replacing the MAF sorts the issue out.

Again thank you for taking the time to help me out.

Just replace with a GENUINE bosch one. Be worth itin long run as the aftermarket ones are crap and fail else engine doesnt like them.

Tis very rare im right so im delighted!!!!!!

Just replace with a GENUINE bosch one. Be worth itin long run as the aftermarket ones are crap and fail else engine doesnt like them.

Tis very rare im right so im delighted!!!!!!

 

+1 I replaced mine (diesel) with a genuine BOSCH one just after I got the car, seems to be a common concenous that other random brand cheaper ones have a service life of between 3 and 4 minutes. Should be fine to go through NCT with MAF unplugged (or not fully plugged in) I would have though as it only reverts to a set failsafe? While waiting for the new bit.