ABF Revs sticking + poor fuel economy

[oakgreengolf]

I Put my ABF lump in my mk2 about 5 months ago now, and every now and then when idling the revs rise up as much as 2500rpm. Ive checked all the normal stuff. The throttle body is clean so are all associated pipes, there are no vac leaks or splits in any hoses. Ive also changed both the sensors on the throttle body. The accelerator cable isn't sticking either. One other niggle is the fuel economy is very poor. How does one test the lambda to see if its working? Any suggestions greatly appreciated.

[danny_p]

mine did this hunting trick a few times,  it was getting to be a right pita in traffic  never pinned the actual reason down tho     it went away after changing the rad and thermostat

[oakgreengolf]

Well it had a new thermostat and the rad seems fine. Really annoying 

[jamie16v]

funny enough, mine used to do this too.
 i havent noticed it for a while, i changed the coolant not so long ago too..

[danny_p]

mine allways did run a bit warm and only played up when running warm....   the problem was the new stat opend late.   so put an old one in that opend at 82 c like it's soposed to.  don't know how it would affect it but it dint do it after and it's not thrown up any fault codes ether 

[eightyeightmph]

Has it got an ISV? My mk3 used to be a pig for this, until I blasted it out with carb cleaner & it runs great now.

Mine used to stick at 2300 randomly, hot or cold. Just sprayed carb cleaner through the ISV & let it dry, also if you look theres a blob of yellow (?) paint on the one end which covers an allen key head, give that a twist back & forth after you spray, leaving it in the postion it was when you started & it should idle happy after a second or too to find itself.

Beats forking out £300+ for a new one from the stealers!

[oakgreengolf]

ive given the isv a good clean also. Car was rough again this morning, revs dropping this time. however was fine on the way home from work very annoying 

[tshirt2k]

Have you tried the coolant sensor? Poor economy could be a sign of that. Revs raise when car is cold and fueling goes richer..

[oakgreengolf]

might be worth a go. 

[tshirt2k]

Definately. its a common fault. The ABF needs everything working within spec to run at its best. Even diagnostics don't help cure problems. Its limited on thes engines.