should disconnecting the boost sensor on my 88 t2 make any difference at idle? the sensor itself checks out fine, the boost gauge is fine, but the voltage at the ecu always reads 5v from the sensor, whether it's plugged in or not, and whether the car's idling or not...

Charlie

 

Yes, thats no good. At idle I get 1.14volts. At fuel cut I get 3.6volts. If I let off the throttle at high revs I get .40volts. Its almost like your reading the reference voltage instead of the output. Are you on pin 2B for sure?????? Is your factory boost gauge showing movement under boost? If not, you've got a problem.

 

speaking of boost sensors, are they compatible between s4 and s5?

 

yeah, the factory boost gauge is fine, and the sensor itself checks out fine. I'm reading 2b for sure...

should the idle change if the boost sensor, or the vacuum line to it, is unplugged? Because it doesn't. The car appears to run well regardless... I'm not sure what the story is.

Charlie

 

I noticed on a series four the voltage output of the pressure sensor at 3.9 inhg is supposed to be 2.5 to 3.5volts. But on a 89 series five the figure given in the fsm is 2.8 to 3.2. Maybe they just clean up their figures or maybe there is a slight difference.

The above figures were for N/A. Turbos as you know are different. Considerably different. As in non compatible. I mean n/a vs turbo different.

Bottom line is I don't know for sure. I'd have to ask a dealer and I'm not in the market for one.