Guys,

After working on my low boost problem for months I have now come to believe that my gauge is bad. I hooked up a pressure gauge to the intercooler and measured 8-9 PSI max. and 6 PSI while the factory gauge was still reading vac. or 0 boost. I need to know several specs. to help in my trouble shooting.
1.) At what pressure does the stock waste gate start to open on an '87? (mine was about 6 PSI)?

2.) What was normal boost for a stock '87 TII?

3.) Fuel cut occurs at what pressure on an '87 TII?

4.) What should the voltage reading be a teminal D of the boost sensor at say....6 PSI or any pressure for that matter so I can check mine. I used the factory manual but mine was only slightly out of spec. and the spare I have read exactly the same...plus the factory manual only uses vac. for the spec.

5.) Lastly....I measured boost at the intercooler (where the ABV used to attach). Should this be the same as the pressure read at the place where the boost pressure sensor attaches?

Thanks for the help.

TOdd

 

All the facts your looking for seem to vary car to car, so it's tough to say.

Stock boost in 87 was 5-6psi I believe.
Fuel cut is also inconsistant but around 7-8 psi, it actually works on voltage from the boost sensor and I can't remeber what it is.

I'm not sure what the problem is here. I suggest purchasing an aftermarket gauge and just forget about the stock one it's useless most of the time. I used a nipple on the back of the upper manifold for my boost gauge. I get a pretty accurate reading.

 

You should hook a boost gauge up to the manifold; otherwise you don’t take into account the restriction in the intercooler pipe, throttle body, plenum and runners. It will read different, but not as much as you’ve experienced. Don’t rely on the stock gauge; it sucks. Get a quality aftermarket one and tee is into the stock pressure sensor line.
It’s really difficult to actually tell when the wastegate starts to open without removing it and bench testing it. It’s usually 2-3psi before max boost. 45.2kPa or 6.56psi according to the FSM. 8.6psi. Check out the Team FC3S DIY FCD write-up, it includes a graph of the boost sensor’s output. No, see above.
Hope this all helps.