Have I reset my ECU!?

[GusPW 0]

I disconected the 3 earth points on the engine (underneath the ISV) the other day to clean the connections (ignition problems). After reconecting everything I took it for a drive and it felt quite good in 1st and 2nd, but then backfired like mad in 3rd and 4th.

Backfiring has pretty much stopped now but it did start doing in 5th when going down the motorway.

 

Have I managed to disconnect the ECU and wipe the settings?

If so is there anyone in the Reading or surrounding area with VAGCOM who would be willing (and has the time?) to help me with the reset procedure? I've never done it before so dont know how long it takes.

I need to sort it out so I can drive down to Wales on Friday! Any help would be much appreciated

[Kevin Bacon 5]

If you're talking about a VR6, then no, those wires are sensor grounds, not ECU grounds.

 

All you will have lost is learned adapatations anyway, nothing important.

 

I think you've disturbed something else by the sounds of it.

[GusPW 0]

Oops! yea forgot to say, its a 94 VR6 (but with early type MAF).

 

Well if loosing those learnt values didn't cause backfiring then I dont know what else it could be.

I disconnected the TPS, ISV and Plug leads 3 & 5 from the coilpack to get access. but I'm pretty sure I put them back on properly!

Any ideas?

[double-6s 0]

I'd start by swapping 3 and 5 leads round to check that.

 

Then make sure anything else you unplugged is properly connected.

[dr_mat 0]

Ok, given that the only thing you did was disconnect some sensors then reconnect them, go and do it again. In my experience if it was working before, and now it isn't, it MUST be something you did... :)

Failing that, the ECU reset procedure is documented round here somewhere - you really only have to cut power to the ECU for a minute or so and it will go into quick-learn mode when you reapply power so go for a drive and do some varied driving (constant part throttle acceleration, constant full throttle acceleration, zero throttle overrun etc etc across a wide range of revs) and it'll learn the engine and it's sensors pretty quickly.

[GusPW 0]

I have checked all conections and they are all fine. I have driven it around a couple of times and very roughly followed the procedure for re-learning sensor values and the engine is back to normal (i.e. lumpy idle and mid rev range) which is why I thought I must have disconected the ECU, but I also read that there is no point doing the procedure unless you then do the basic setings procedure on VAGCOM.

Is it worth me doing the VAGCOM stuff now or does it need to be done soon after doing the ECU reset?

 

Hi Dr_Mat

Is there any chance I could pop over to your work sometime this week to use your VAGCOM, I need to wipe my fault codes as I will have generated a load by unplugging things.

[dr_mat 0]

You shouldn't have error codes unless you unplugged stuff while the ignition was on, and if you're going to reset the ecu it will lose them all anyway ... but if you want to clear the ECU you'll have to give me a few days notice to bring the laptop in.

 

I don't have a registered vagcom so I can't do the full procedure, btw, I can only read error codes and measuring blocks.