Drove to work this morning (2 miles) and Autometer AFR showing slightly rich and car stinking of petrol. Seemed to clear up on the run home after work...

Fitted new Forge header tank tonight and took her for a run. Got half a mile before the AFR gauge dived past red and showed nothing No noticeable change in engine noise or performance though.

Tried switching off and starting again, but still off the gauge lean.

Picture of header tank below shows tight fit against MAF. Could it now be knackered due to heat/vibration off the header tank? would a knackered MAF show up as lean AFR? Or am I way off the mark....



Brief relevant spec:

'93 WRX
Apexi PFC & AVC-R
Apexi Induction
Fuelab Reg
FSE pump
550's

 

Sounds like a lambda on it's way out to me....

 

Now there's the thing....I knew the lamda was fecked as WUZ and Andy F told me that at mapping a couple of weeks ago.

Andy somehow "bypassed?" the lamda for mapping the car and disconnected its function on the PFC. No idea what that actually means though. Since mapping, the AFR has been fine, showing mainly stoich going into slightly rich. Its just today that its gone a bit **** up.

Maybe the lamda was partially functioning, but has finally well and truly given up the ghost now?

 

I would expect that Andy would of used his own wideband lambda during the mapping, so would of turned the lamda control off.

If Andy has left the lambda control off on the PFC then they AFR should be fairly stable at idle/cruise around stoich (if the map is any good, which I don't doubt).

If the Lambda control was switched on, you should see some oscillation on the AFR as the ECU tries to maintain the ideal stoich mixture. This will continue to oscillate during cruise. The faster you cruise the faster the oscillation.

Although it doesn't go quite as fast or mad as the OE ECU.

If you have an FC commander you can turn on/off o2 feedback control (it's in etc... menu).
If you switch it on at idle you may find, with a knackerd lambda, that it'll start running rough/differently.

 

Thanks for your input Scott. Yes, he definitely left the lamda control off as the AFR was very stable previously.

Ran rich again this morning after about a mile, so god knows whats going on.

I'll check out that function on the commander, though I think I already know the answer to that one...