Try driving the van for a while without the O2 sensor connected.
At least that will narrow down your area to look at.
Thanks again for all the advice. After a full week end of testing the simple solution from Roger and Scott has given the best results (just unplug the O2 sensor)
The list of things checked/reviewed/cleaned is a couple of pages of info, but nothing made a difference.
The down side is there is such a relationship between the AFM and the O2 sensor, i just can’t make sense of it all.
Each time I swapped AFM’s, the symptoms changed slightly (even though all three ran fine on my old motor). Each measure different when checking also!
Similar, I tried three different AFM’s, two used, one new. All three the heating element had the same resistance (and confirm power supplied to the plug), however all three read a different voltage with everything else the same. (EG the C02 in the exhaust should have been consistent, but each gave a different voltage)
So I fittied the AFM that gave the best running with the O2 sender unplugged, and connected the new O2 sender.
At least it runs, however not perfect. (still occasional hesitation and power delivery not as smooth as it should be).
It still runs nicer with no O2 sender connected.
I’ve not swapped ECU’s, or put in new spark plugs, but these all check out OK.
All the testing was done on a ~5km loop with varying engine loads to test (and all at full operation temp). I have not done a long run yet, which often shows up other issues!!
Anyway, at least it seems to run for now!
With the O2 sensor disconnected, the computer uses its standard set of values through the fuel maps and you will be surprised how well it runs.
My 2wd panel van is getting 10.8L/100km combined highway and city driving with the O2 sensor just a distant memory.
Good enough for me driving a huge brick over 105km/hr most of the time on the freeway
I tend to agree Scott, (I’d be very happy with 10.8!!) I’ve been persevering to run with the O2, but no luck so far. It did surprise me though, with the O2 sender disconnected (new, Bosch, 3 wire) and the engine idling fine, the output voltage from the sender was varying quite a bit, which means the exhaust gas is varying despite it seems to be idling OK.
The same test was also a different voltage with each AFM, despite they all seemed to idle OK.
I’ll try a few more combinations before I give up and run with it unplugged!
One point that I do not know, if the ECU stores memory of inputs (the manual notes ECU needs to be powered down and on again when swapping components) to clear memory. Ho long before this resets?
For example, in modern cars it averages a lot of values, so it takes quite a few drives (often with the same diver/driving patterns) for everything to even out and run correctly on a new component.
Not sure if our ECU’s do that.
I think our ECU’s are a lot more simple and just have the factory input values. It would just have maps based on a variety of input values and that would be its limit.
Agree modern computers remember driving style and load use etc and adjust to suit.
That is interesting Scott, as I think some of the issues I had over the week end was I would swap parts, and it did not make much difference.
However this week, I have done multiple trips without changing anything (on two separate set ups/combination of parts) and it appears to get better after a few drives (and a few cycles of cold to hot), including a run on the highway. I have one more combination to try before I pick one to leave in the car. The set up from yesterday ran the same with and without the O2 sensor connected. (though I would like to do this across a couple of tank full’s of fuel to see if economy changes)
I found a few interesting articles in the Samba. When I get time, I might have a go at setting up an AFM from scratch (someone wrote a procedure using an O2 sensor output). I’m still surprized just how different each AFM I have is set up.
More motivation for me to get the shoebox electronics kit I have connected to an ECU!!
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