advice on a slight hesitation ?

[WRC WILL]

Not been a Scooby owner very long so be grateful for some advice,
Here it goes, car a UK classic facelift 2000 wagon completely standard apart from a rear box.

When driving between 2500-3500rpm the car hesitats/holds back then clears and is fine again ? This happens in any gear and didn't matter if its hot or cold,

I recently this weekend fitted a new 02 sensor as it had thrown this code up on a check so thought this was my problem but it clearly didn't fix it

I have checked for boost leaks as good as I can, and checked air filter box, and the maff sensor had been replaced recently according to previous owner,

What would people suggest to check or replace next?
Maybe spark plugs ?

[Scott.T]

If O2 has been replaced along with MAF then plugs would be the next best bet.

2,500 - 3,500rpm is around the region the ECU switches from closed loop (O2 fuel control) to open loop (MAF fuel control) depending on loading/boost/throttle position.

You can run with the O2 disconnected, so try that for a bit to see if it changes anything.

[WRC WILL]

I will order a set of plugs up, and try that 1st,
I problem only occurs if I'm driving normally and increasing the revs steadily, if I plant the throttle it doesn't happen, so would the throttle position sensor cause this sort of problem ?

But will do plugs and try running with 02 sensor unplugged and go from there.

[asperformance]

have you actually re-set the ECU, if you have saved codes/learning from previous issues and then fit new parts it often messes up anyhows...............

on a classic simply disconnecting the battery for 15-20mins will re-set everything

[WRC WILL]

I have done the joining of the black and green plugs to reset the ECU after I done the o2 sensor which showed fitting the new one cleared the faulty o2 sensor code ?
Do you have disconnect the battery as well then ?
As I thought joining the plugs reset the ECU ?

[EXEVO3]

The green plugs test all the relays fan ect are working...black plugs are to read the fault codes...
to reset ecu you need to disconnect batt buddy

[andy-m]

Originally Posted by EXEVO3

The green plugs test all the relays fan ect are working...black plugs are to read the fault codes...
to reset ecu you need to disconnect batt buddy

on V1/2, yes. on the 3-6 ECU's I thought you had to connect all 4 and do something with the throttle to do a reset. Not had one before but think I read something like that somewhere

[WRC WILL]

I had the engine light come on, so plugged the black leads together and got code 32 o2 sensor,
So I plugged the black and green ones together and held throttle on then half way, then started it and went for a drive as the guides say this resets the ECU and if fault is clear it will just flash on and off when ECU is reset, but mine just flashed up code 32 again,
So I replaced the o2 sensor, redone the black and green plug retest and the fault was cleared. Showing that the ECU had reset itself ?

So on my 2000 reg UK turbo do you need to disconnect battery or are the guides correct when just joining the green and black plugs it resets the ECU ?

Confused lol

[andy-m]

that sounds like what I read you needed to do for facelift ECU resets.

[Scott.T]

What you have done is perfect for any classic.

[WRC WILL]

Think I found the problem, ordered new plugs but before fitting them I had another good look round and noticed on the pipe after the maf sensor underneath it was slightly deformed so removed and reffited the pipe with a new jublie clip so its sealed and the problem seems to have gone away (touch wood).

So looks like it was pulling air in after the maf sensor causing the hesitation.