If the WOT switch in the TPS is closing (electrical continuity) when the thottle is wide open, the TPS is working correctly. But make sure that the idle switch opens when the throttle is cracked.
I think my first suspicions in this case would be low fuel pressure/delivery (run the fuel system test suite in the Bentley manual) or a bad AFM.
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Violent cutout at WOT. Not TPS or fuel...
I recently picked up an '89 325i for $250 and have been working through a few items on the car. The newest issue however has me a bit stumped. Whenever going WOT the car violently cuts in and out essentially "bucking" the car before it eventually catches itself and accelerates normally. It doesn't matter if the car is off idle, at 2500 RPM or 5000 RPM at WOT it cuts out. If I was to go say 75% the car will carry all the way to redline in any gear so I suspect it isn't fuel related...
Thinking through things I've pretty much settled on the TPS being the problem. Reason being is that when I unplug the TPS the car accelerates without any of the hesitation all the way to redline (albeit without the ECU dumping in fuel).
Thing is though I tested the TPS and had the "click" off idle and also have continuity at both idle and WOT on the prongs. So suppossedly the TPS is working correctly. With the above in mind I'm thinking it could be one of the following:
1) ECU not giving correct signal for fuel
2) Fuel pump cant scavenge enough (although without TPS it will go to redline and seems to be RPM independent)
3) Some other problem that I'll keep trying to find...
...next thing I will do is test the fuel pressure under load to make sure it isn't cutting out. Any other ideas?
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