AFR Gauge

[e21Mark]

TPS replaced (it wasn't hugely expensive and as I had it anyway) and a marked improvement in throttle response. Still some hesitation though and clearly over fuelled judging by the popping and banging on overrun. New lambda (Bosch part to replace pattern item) and over fuelling cured. Still hesitating intermittently though. A quick check of the rear fuel filter and it looks decidedly "second hand". Decided to replace it and all is well once more. I realise the TPS might have been an avoidable expense, but the condition of the fuel filter typifies why I wanted to work my way through the car and replace these parts. At least now I know exactly when all these parts were fitted and can be confident the car is less likely to fail, down to neglect.

Many thanks for all your input chaps. Much appreciated.

[Pumaracing]

I'm not really sure how if the A/F reading was spot on stoichiometric at all times (14.65 plus or minus a bit) that any fault could have been present in either the lambda sensor or fuel filter as clearly the closed loop system was working correctly. If the lambda sensor was faulty the A/F ratio would go to hell in a handbasket and if the fuel filter was blocked you'd get fuel starvation at high power outputs. Anyway, mine not to reason why....

[e21Mark]

The saga continues...

As I wanted to get everything in good order, I replaced pretty much everything on the ignition side. I also replaced the TPS, as already mentioned, where things appeared to have returned to normal. Unfortunately it didn't last for long though and the rough running is now between 2 & 3k revs, whilst under load. The AFR gauge has started to read HEAT pretty much constantly.

I checked the fuel pressure and found the filter was pretty much blocked, so replaced it. I have also bought a new lambda sensor, which I'll be fitting tomorrow morning.

I know that E30 M3's running Alpha N can often suffer some flat spots but this has only started recently. Is it possible for maps to be corrupted in any way? Am I being misled by the odd AFR gauge readings, or do they point to a fault somewhere, that would explain the rough running?

Clutching at straws, I was caught out and bought my last fuel from Tesco. I have heard that other people suffered poor running after filling up with Tesco fuel, so am topping up with Esso just in case.

Finally, can anyone advise on the lead needed to connect a laptop and check the map?

Thanks in advance.

[stevesingo]

There is a version of the MAXX that has closed loop WBO2. Do you have this?

Can you access the MAXX software with a laptop?

Register at http://forum.s14power.com/register.php There is a lot of MAXX experience available on there.

[e21Mark]

Thanks. I've just posted a thread there, so fingers crossed.

[fatjon]

Pumaracing said:

I'm not really sure how if the A/F reading was spot on stoichiometric at all times (14.65 plus or minus a bit) that any fault could have been present in either the lambda sensor or fuel filter as clearly the closed loop system was working correctly. If the lambda sensor was faulty the A/F ratio would go to hell in a handbasket and if the fuel filter was blocked you'd get fuel starvation at high power outputs. Anyway, mine not to reason why....

When the Techedge goes faulty is stakes the anolog output at around stoich and displays around stoich as a best effort at getting you home without a dead engine. If it is sitting there or thereabouts and does not blip rich significantly on AE or dip on overrun either the EMS is the most amazing system on the planet and reacts before the gauge can even report the change from stoich or the lambda system is stuffed. The intermittent display of "HEAT" for more than a few seconds is another massive clue from the Techedge firmware. It means I'm hitting the sensor with current on the heater circuit and it's not getting hot enough. I have used these Techedge devices extensively and it is yelling aloud that it's fubar. By "it" I mean either the sensor or the Techedge WB controller. It will need some competent diagnosis to figure out which. I have had one or two failures on the 2J range of bottom end controllers but sensors of course have the harder life.

[e21Mark]

It turned out to be contaminated fuel. I replaced pretty much every sensor and ignition component, with little or no improvement. As a final straw we drained the tank and the fuel looked decidedly suspect. Once replaced, it cleared and now runs better than ever. The AFR gauge is also working perfectly.