Over fueling fault chasing
Discussion
Good afternoon all, seeking advice / experience on chasing a clear over-fuelling issue (sickly rich smell from passenger side exhaust)
Diagnostics output of a cold running below (I’m hesitant to run too long and up to full temp for fear of ruining the cats)
To me, diagnostics are showing clear delta between banks on lambda and adaptives. Adaptives are hugely in the negative, suggesting to me unburnt fuel.
I haven’t looked at plugs or swapped plugs, injectors or lambda sensors yet. (That will clearly be my next job)
I’m questioning myself if this is a lambda fault as the trace and difference between the banks looks very odd to me.
Thoughts / options / experiences?
Diagnostics output of a cold running below (I’m hesitant to run too long and up to full temp for fear of ruining the cats)
To me, diagnostics are showing clear delta between banks on lambda and adaptives. Adaptives are hugely in the negative, suggesting to me unburnt fuel.
I haven’t looked at plugs or swapped plugs, injectors or lambda sensors yet. (That will clearly be my next job)
I’m questioning myself if this is a lambda fault as the trace and difference between the banks looks very odd to me.
Thoughts / options / experiences?
Morning!
Yep, the traces look alarmingly high.
Some years ago had a similar issue. Engine was running dog rough!
After returning home and removing airbox/filter, scuttle panel to access throttle bodies....and looking at airflow through throttles....and wondering why I couldn't reduce airflow to the proscribed flow at idle...I had a lightbulb moment.
The flows would reduce if I "helped" to close the butterflies. That's when it dawned that the return spring on the throttle cable was not doing a lot! I adjusted the return spring tension so that the linkages to the butterfly spindles were 'properly' closing. I then re-checked individual throttles to confirm flows, and all was good.
You do need a flow meter to verify airflow through the throttles.
I'd be reluctant to swap lambda plugs until you've checked airflows.
By your own admission, you've noted strong smell of unburnt fuel and noted that the ECU is trying to reduce fuel injection - by a substantial amount. I'm not an expert (Joolz at "Kits & Classics" on here is!), but as I understand, the only variable you can adjust easily (without re-programming) is the airflow, as that directly affects the injection of fuel.
Nick
Yep, the traces look alarmingly high.
Some years ago had a similar issue. Engine was running dog rough!
After returning home and removing airbox/filter, scuttle panel to access throttle bodies....and looking at airflow through throttles....and wondering why I couldn't reduce airflow to the proscribed flow at idle...I had a lightbulb moment.
The flows would reduce if I "helped" to close the butterflies. That's when it dawned that the return spring on the throttle cable was not doing a lot! I adjusted the return spring tension so that the linkages to the butterfly spindles were 'properly' closing. I then re-checked individual throttles to confirm flows, and all was good.
You do need a flow meter to verify airflow through the throttles.
I'd be reluctant to swap lambda plugs until you've checked airflows.
By your own admission, you've noted strong smell of unburnt fuel and noted that the ECU is trying to reduce fuel injection - by a substantial amount. I'm not an expert (Joolz at "Kits & Classics" on here is!), but as I understand, the only variable you can adjust easily (without re-programming) is the airflow, as that directly affects the injection of fuel.
Nick
Edited by nawarne on Monday 29th January 10:20
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