On the 20XE, what monitors the mixture and controls whether its too rich or lean? I'm stabbing that on modern cars the lambda sensor plays a part? Put on my 89/90 mk2 Astra XE it doesn't have a lambda sensor. So how does it know what its doing?
Took the Nova up to SCA in Norwich yesterday afternoon to get a power run done on the rolling road to find out what she's doing and if everything is ok.
Unfortunately they wouldn't run it.
At idle the lambda reading was about 1.4 (normal is 1.0, above this figure is lean, below is rich, so they tell me?) so was a little lean. But when they put on a few revs up to about 2-3k it then went all over the place - even up to 4.0! So they wouldn't run it because it could be harmful to the engine and advised I take it easy on the road until the problem is sorted.
In all honesty I have none. My assumptions are that without a lambda sensor the ECU must purely rely on the AFM. So its either a problem with the ECU or AFM.
Something else that was pointed out to me yesterday was that whether I had uprated the fuel pump. I'm using the standard SRi pump - do others uprate theirs for an XE conversion?
hmmm 1.4 is lean, but so what, it wont do any damage at idle as hardly any fuel is required
and at ~2k at light throttle it will be lean, most manufacturers do that to get good economy
without lambda ecu uses its own fuel map and wont budge from it, with lambda theres a (rough) 10% adjustment
take it there are no faults and its not in limp wrist mode?
it might actually be fine under throttle & lambda isnt used anyway under throttle movement or over 3/4 (iirc) throttle
well it wont be steady, but i would do a couple of things. firstly check pump has a good 14v when running.
weld lambda sensor boss in and get a sensor & display for it to see whats going on
then if its the same clean injectors, get new fpr or crush yours to get idle lambda to 1 (wont be much) or change ecu & loom to include lambda control
I would expect this to be similar to the turbo: If the oxygen sensor is dead/missing then the ECU uses a replacement value so that you can drive home, slightly on the 'rich' side (the ECU light is on of course)