Woooo Hooooo! Sorted!

[mhyphenl 10 1 Cars]

I've only gone and bloody fixed it!!

 

I've spent many hours on here posting around my issues with the MIL light being on and emissions problems, my cars a later DKZ model so everything is very much under the control of the ECU. I'd replaced everything, several times in some cases! Sensors, two or three AFM's, a long discussion about which ECU is correct and several ECU's, still this little yellow light would come on after a minute or so of driving! I spent a long time eliminating leaks, changed the Lambda twice because a fairly expensive bit of testing kit told me they were faulty and then, yesterday the penny dropped.

 

I was convinced that I had a leak on the exhaust but before the lambda as the emissions were rich but the lambda said lean. I was certain that there were no leaks before the inlet and that every sensor was spot on. The diagnostics guy who was helping me out was putting his lambda sensor tester on and that was saying that it was going to ground on both wires, checked the wiring and it was fine, not a faulty ECU unless I was unlucky enough to have 3 with the same fault, he sent me away with no resolution. I decided to attack it with my primitive multimeter.

Turns out that both wires on the lambda do go to ground when the engine isn't running, worth knowing if you own one of these cars. Next I made a couple of leads up so I could measure the Lambda while the engine was running, started her up and as usual 0.2 volts not moving even when revving, lean!! Then I noticed it, it was showing minus 0.2 volts and that shouldn't be possible! Took the connector off and measured voltage across the ECU terminals, 0.45V which is correct, (essentially the ECU setting itself at lambda it the connector comes undone!) It struck me that the only way a negative voltage could register is if the earth and the signal wire were the wrong way round. Released the terminals and swapped them over and bingo, a nice signal bouncing around between 0.35 and 0.55 volts. Rev or idle and it was adjusting itself nicely.

In my utter excitement I ran round to look at the dash and finally the little yellow light had gone out and it was running sweet! Only took about 5 years!! I just never thought that anything on the loom would be the wrong way round, to be honest it looked unmolested!

 

I enjoyed my first drive to work this morning without that little yellow light and it was great! Thanks everyone for all the suggestions and help, there are many things on my car that are much better because of them.

 

Have a merry Christmas

Martin

[tartanbloke 35 1 Cars]

Congratulations and the feeling of resolving something is just euphoria.

 

Merry Christmas and enjoy your car.

[Tom Fenton 1,542]

Well done for sorting it. It's a great feeling when you finally track down and sort a tricky fault.

[toolie72 67 1 Cars]

Well done!!!

 

Now go and give some Audi drivers a fright!!

[mhyphenl 10 1 Cars]

Ha ha, yes I've done my fair share of that. Unfortunately the car isn't as fast now as it was. Must have been running quite rich on acceleration. Looks like I'm going to get a lot more MPG though (not quite as exciting!)

[Henry Yorke 269 3 Cars]

It is brilliant when you finally crack one of these. I had one similar on my CTI turbo recently, which turned out to be a blocked catalyser as the front part had collapsed and blocked the rear. This must have been slowly going over time and was really highlighted by the fact it wouldn't boost correctly. Cleared it out and found an extra 70bhp!!