Funny boost gauge readings

[Momar]

I know that on most cars factory boost gauges arent usually relied upon for acuracy, but I just bought an 86 GN, and the factory boost gauge is acting real funny. I am trying to get it all working properly and fully tuned up before I start modding. The vac line to the map sensor wasnt even connected when I got the car. Without it connected the boost on the gauge always showed full. Then I connected it, and it started working again. It still isnt right though. Now, if I just barely touch the pedal and it pegs the boost gauge. I know it isnt making that much boost, because you arent hardly accelerating. If you push the pedal down to the floor it kicks you back a little, and you can hear the turbo spool up. Once you put the pedal down, even before the turbo gets spooled up you have the boost gauge pegged into the red.

My question is, is the computer seeing the same thing as the boost gauge. The way it acts, it is seeing atmoshperic pressure as full boost. I think this because w/ the vac line unpluged it shows full boost on the gauge(15+) I think that this has to be either a problem w/ the gauge or map sensor. I am betting on the Map. I am going to hook it up to a scan tool tomorrow, and check to see what the map is reading, and check to see that the other sensors seem to be reading w/ in range. The car seems a bit slower than it should be, and I am guessing that this could have something to do w/ it.

Any opinions/suggestions welcome.

Thanks

Ben

 

[Momar]

Well, I still have the funky boost readings, but I found one of my problems. The y connector that goes to the wastegate actuator, and to the turbo, was in there wrong. I routed the lines right, and the power band is much wider, and pulls much smoother. I am getting the bugs worked out. Hopefully I will have them all taken care of soon, and will be able to start modding.

Ben

 

[FJM568]

1st...The factory boost gauge is junk...

2nd...The ECM doesn't "see" boost...It doesn't know how much boost you are making, because the ECM doesn't reference the MAP sensor...

Get an aftermarket boost guage and see what is really going on...

 

[Momar]

Yes, I figured that the factory boost gauges werent very good, I just wanted to make sure that the computer didnt see what the map sensor was showing just in case. I should be getting a real boost gauge within a couple weeks. I am getting a used one from a guy.

 

[Momar]

Well, I just scanned my car. The 02 sensor is very lazy. What is a good source for the denso 02s?

The BLM was 156. I imagine that this is probably because of the 02. All of my other sensors seemed to be within range, and I am not getting any knock.

Ben