Boost Guage

[Duratys]

Seems my boost guage likes to sit at 10psi. Turn the key on and watch it swing and hold. Now I would have expected the guage to be mechanical but with it acting the way it does Im thinkin its getting an electrical input that makes it tick. Where does the guage get its reading from so I can get this fixed when I get home :eam:

 

[PhillyTurboSix]

I've heard about them being problematic in the past. Seems either people have issues with them or they work fine. The gages were done by Denso and long gone from GM's inventory. It gets it's reading from the MAP sensor. Could even be an issue there. Check all the vacuum lines to the MAP as well. Test the 3 bar sensor, The green wire should read 1.5volts DC ignition on, on the sensor as indicated above. Another test, if you unplug and jump the green to gray wire on the plug, the gage should go past 20 PSI. Have someone watch the gage when you do this. And be quick to see if it responds. A paper clip can be used.

Also...
The TTA MAP is wired backwards from all other GM MAP sensors. In the 90's GM decided to make the MAP uniform and if you go to GMpartsdirect.com and try and get a 3 bar, it will tell you a plug is needed. What that plug does is reverse the wiring on the MAP making it then uniform with the other map sensors GM makes.

Why did they wire the original MAPs backwards??? Dunno. Probably has to do with the resistor placed in the harness leading to the MAP that drops its 5volts supply to 4.7volts zero'ing out the dash guage.

Another person did this..

The boost gage is hooked up separately on back of the instrument cluster and it was disconnected when the cluster was pulled out. After hooking it back up the gage was found to be off almost 10 PSI, hence the reason someone must have disconnected it. Anyway what I did was set my air compressor to 10 PSI and then hooked up another test pressure gage on the end of the air hose to verify regulator gage was correct. After doing that I hooked up the hose to the MAP input with ignition on. I then carefully removed the gage pointer and re-inserted at the set pressure of 10 PSI. After doing that I did a three point check (2,10,18 psi) to verify reading was correct and all is well now.

Good luck try those things and let us know how you make out!

 

[Duratys]

Good reading thanx :read:

If the MAP sensor is screwed that would explain the slight surging it has on idle as well. It will be a little better than a month before Im home again to get after this.

 

[PhillyTurboSix]

Well they all kinda surge on idle. That also could be the sign of some rotted vacuum lines. Or a dirty IAC and or out of adjusted TPS. One thing I would recommend even tho the car has super low miles is toss a turbo tweak chip in it. esp. if your going to drive it. These cars came with too much timing and not enough fuel from the factory. A turbo tweak chip with correct all that and he also turns off all the emissions stuff to make the car run smoother. I talked with Terry Shaw one of the major classic car appraisal guys when he was doing my TTA he told me the real low mile TTA's he's seen had major clogged fuel systems. Might want to look into that as well. Sometimes it's bad to let a car sit to much. Good luck with it and keep posting any issues you have with her. We'll have it purring like a kitten in no time!