Buckling/Hesitation under hard throttle?

[Roodosutaa]

Hi all

Lately I've noticed the car occasionally would have an abrupt hesitation and buckle a few times on hard acceleration (not necessarily under WOT), this would go away if I ease up, or if I'd kept my foot down, go away after a few seconds and continue to accelerate. I've had a GIAC tune for two years but this occurs both under stock mode and "fun" mod,e and has only started happening a couple of months ago.

VWvortex suggests anything from dirty MAF sensor, spark plug gaps, leak in the vacuum lines, loss of boost, dodgy N75 valve

Just wondering if anyone here has had similar experience with the buckling so that I can narrow this down a bit?

Also it's thrown a code for the secondary injection pump, seeing as this is more an emissions part, I doubt it has anything to do with it, dealer says it needs a new pump and I'm not about to fork out a grand for its replacement just yet, and I'm aware that the car will run without fault with the whole system removed, as some have done

Many thanks in advance

[buzuki]

Sounds like an air flow meter problem.

[nikanasz]

i've had this issue when i was on GIAC tune. the jerkings were most noticeable during shifting 3rd to 4th gear. also i get erratic idling during cold starts. never got around to solving them though, as i changed to another tune which didn't give me those problems.

but your issue might be different from mine; as you have been on GIAC for a few years. could be hardware wear and tear issue.

[Jmac]

Sounds like a boost cut to me
Jmac

[Spec83]

What is going wrong with all the Polo's????

[Blitzen]

They are getting on in age now... Mind you, I have had 3.5 years of trouble free motoring.

[Roodosutaa]

Unplugged the MAF then drove for a few days, no problems even under hard throttle. The car definitely seemed a tad more sluggish but still better than stock - boost would peak at ~15psi instead of the usual ~19-20psi with the MAF unplugged

Thought the MAF might be dirty so opened up the airbox to take it out and discovered - water - in small puddles on the air filter (have a BMC drop-in) I guess if I still had a stock paper filter the paper would just absorb the water, but on an oiled cotton filter the water would just stay there... how the heck did water get in the air box... and on the top (engine side) as well

Thinking water mixed with oil and dirt might have fouled the MAF hot wire I took it all out, sprayed alcohol on it (which seemed clean to begin with) and let dry before putting everything back together.

Much less bucking now - but it still happens from time to time on full throttle and mostly in 2nd. Have ordered a replacement MAF on the interweb from Germany and will see how that goes

Yes the car's getting on a bit... close to 80kkm now