1989 328GTB what exactly does the throttle position sensor do, how can you test it and how do you work out what position it's meant to be in? Many thanks.
It's not a variable sensor -- it's 2 on-off switches built into a common case. The physical tests/adjustments are: At idle, the snap-action switch on the right in the jpeg should be closed -- i.e., resistance from pin 2 to pin 18 should be 0 Ohms (or a few ohms maximum), and the "flexible" WOT switch on the left should be open -- i.e., resistance from pin 3 to pin 18 should be infinite ohms. At just above idle, both switches would be open. At WOT (throttle open about 60% or more), the resistance from pin 3 to pin 18 should be 0 ohms (or a few ohms maximum). The purpose is: At idle, it inhibits the cold start injector from firing, and limits (or prevents) excursions of the Lambda system (if present) so the A/F ratio doesn't wander so much. At WOT, it "tells" the injection ECU to ignore the O2 sensor signal (if present) and add some extra enrichment to make best power. What version 328 do you have euro (without Lambda) or US (with Lambda)? Image Unavailable, Please Login
wow..thanks steve. i should have said my car is a UK car and has no cats. does that make any difference? i'm not sure if it actually has O2 sensors
Yes, it limits how much that I can help you because I don't have the wiring diagram for a euro 328 Seriously, on a non-Lambda K-Jet system (no cats, no O2 sensors), I'd guess that it's only purpose would be to be a failsafe device for preventing the cold start injector from firing at idle (which it should never do). Enrichment for your model under WOT is controlled by the warm-up regulator, and you don't have an injection ECU. What is driving your interest -- are you having a runability problem of some sort?
the car SEEMS to run fine, but the switch adjustment is turned all the way to one end of it's travel, which i find a bit odd.
