Resetting fuel trims on ODB2

[85jas 0]

Hi all! Just changed the spark plugs on the vr and, judging by the way it drives now, it's rich as a b**ch! Is there any way to reset the fuel trims to force the ECU to re-adapt (i.e. unplug the battery)? Or is it a vagcom job? It's an OBD2 '97 golf.

[VR6Nat 9]

Did you check the gaps on the plugs were all correct? And you can disconnect the battery for 10mins to reset the ecu I believe

[Lukey. 381]

gapping is hard if you are using the proper 2 electrode plugs, i went through that when you helped me sorting new plugs nat, only easy to gap single electrode plugs, if you even have a go you need round feelers not blades and have to gap from the insulator not the tip, which makes the electrode gap actually about 2.4mm not 0.8mm, very confusing. Which is prob why they tell you not to try and gap multi electrode plugs.

you should reset the trims by leaving the battery off then letting it idle for 5 mins when you restart so it gets its baseline back. if you have access to vagcom clearing fault codes resets the fuel trims aswell

[85jas 0]

Thanks for the incredibly speedy replies! The plugs I got are the NGK BKR5EIX - are they pre-gapped? That's very confusing about the gaps, I always assumed it was tip - ground, not insulator - ground! :S

Its a bit strange, as soon as I changed the plugs the car ran beautifully smooth but after half a mile it all started to get a bit rough... and now after 5 miles it's seriously misbehaving :-# Initially I thought it was misfiring but it kangaroos lots at low revs so it's gotta be the fuel. Right? Steep learning curve this is for me!!!

[Rikki 2]

Disconnect the battery.....leave ignition on for 3 mins then let idle for 3 mins without touching the aceelerator pedal!

[85jas 0]

Right, done it - seems to have smoothed out deceleration when coming off the accelerator, but I think the engine is misfiring too! Aaaargh!! +o( I unplugged the MAF and went for a spin, that hasn't made a difference... Next stage, new HT leads I guess! I think the ones I have are originals, are the originals red with the cylinder number printed on each lead?

The magnecors seem to be what everyone uses here, do they have the connectors for the coilpack / sparkplugs or do they require soldering? Thanks all!!!

Guess I'll be getting the train this weekend :@

[andy 0]

You sure you haven't just seated a lead on a plug badly, its easily done on a VR.

[85jas 0]

Yeah they're pretty deep and somewhat inaccessable... I had a poke around this morning and managed to electrocute myself mildly off plug 3 - its arcing from the point the wire joing the plug housing. D'oh!

New leads. Phew

Thanks you guys again for all your help!!!!!

(edit) PS Out of interest doing the ECU reset has smoothed up the cylinders that are running properly when decelerating, it is worth doing a reset every time you put in new plugs?

[Lukey. 381]

red genuine leads are what id get again

gen ones are the only ones that have the vw logo and part number on them

the wierd gap setting is only for multi ground point plugs, i did find a guide by ngk themselves but cant find it now

[ASHLEYG 4]

Wrap some insulating tape around where the lead is arking out as a temporary fix so you can carry on using it!

[85jas 0]

Hehe insulating tape, I was wondering if some sort of sealant would do the job but hey, the VR deserves better Having said that, just got some pants £30 leads to tide me over :-*

Lukey, guess the originals have stood the test of time - the other 5 leads are still in great shape, hmmm I wonder if I can find just one original lead, just to get that lovely red back in the engine bay Like the look of the screen-grounded dubpower leads but they're just too much - got the MOT in december so saving up for lots of bits and bobs :S

[Lukey. 381]

some other members have got single red leads from VW