warthogtech Posted August 9, 2008 Report Share Posted August 9, 2008 my boost gauge hasn't worked since i got the car. it goes to 0 but stays there at all times. i changed the boost sensor and that didn't do anything. does anyone know where and at what values to shoot for power coming from and or going to the boost gauge. it doesn't bother me that it doesn't work because i have an aftermarket gauge, but i'd would like to verify that the ecu is getting the proper info that it needs from the boost sensor. it's an 86 and any help would be greatly appreciated. THANKS!!! Link to comment Share on other sites More sharing options...
mikec Posted August 9, 2008 Report Share Posted August 9, 2008 The earlier model year cars - those with the firewall mounted boost sensor - also have a control solenoid for the sensor. This solenoid routes the boost sensor input to either the engine/intake manfold or to outside air. Every two minutes or so, the ECU trips this solenoid to get a snapshot of outside air pressure; from this the ECU can figure out what altitude you're driving at. If that solenoid is bad it can screw up the boost sensor input. Also, there are small white "check valves" in some of the vac hoses. They're supposed to be in the hoses feeding the dash vents and the cruise control system to keep boost pressure OUT of those two systems. If your vac hoses are mis-routed it's possible you've got a check valve blocking boost signals to the sensor or it's tapped into the wrong vac hose system in the first place. I believe the boost sensor & solenoid are supposed to tap into a vac port directly above the "row of three" on the side of the throttle body; the factory hose has a white marker stripe. It should go from the throttle body port to the end-port on the solenoid - on the end further away from the side/center port. The side/center port goes to the boost sensor via a yellow tagged hose. And a blue hose goes from the remaining solenoid end port back towards the cold air inlet for the car. Notice there are NO check valves (they look like little white hose couplers) in the boost/solenoid circuit. One thing you can do as a temp test is to start the engine and let it idle for about 3 minutes (so the ECU takes at least one "snapshot" of ambient air pressure) and then run the "white" vac hose from the throttle body directly to the boost sensor - bypassing the solenoid completely. Go for a drive and see if the boost guage works now; if so you know it's a solenoid or ECU control to the solenoid issue. mike c. Link to comment Share on other sites More sharing options...
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