Hi everyone, I have a question for you guys and I hope you guys will help me figure out the problem with this mazda. It is a 1990 Tii, motor was supposedly rebuilt not too long ago.. It is only boosting 4.5 in all gears, so what do you guys think it is? Its not smoking out of the exhaust or anything so turbo seals are good as far as I know. Could it simply be the boost solenoid? or cracked turbo? vacuum leak?
Thanks for any help in advance!

 

Yes.

 

More than likely a boost leak, the boost solenoid wouldn't cause you to have less boost than the WG spring.

 

Could be guage/line as well. I would run a temporary line off the uim to rule that out.

john ny

 

Great answer speedoflife...

Thanks for the input guys, I think the boost gauge or line are okay though.
Is the wg spring set at 5psi? Wouldn't a boost leak be inconsistent at different gears though?

 

You practically answered your own question, you were already on the right track. Now you need to go find out if it really is any of those things. Diagnostics often require getting under the hood.

A boost leak could be inconsistent through the gears, but 4.5psi isn't far below stock levels. There could be a small leak.

Your wastegate could be faulty, or your gauge. I would hook up a new gauge to know what you're actually hitting like someone mentioned. And just so you know you have no leaks, test thoroughly for them. When I thought I had just a couple leaks I used a boost leak tester and found 6 or 7 instead. Fixing those made a HUGE difference.

 

Okay, thanks a lot man. I can't really go and start testing since its not my car yet so I was just trying to figure out if its not something major like a cracked turbo. Thats pretty much out of the question right?

 

I don't think a faulty turbo is out of the question, but if it is they are cheap and somewhat plentiful.

 

Thanks for your help guys, looks like its gonna be a great community to join

 

A stuffed catalytic converter/exhaust system, can cause low to little boost.

What kind of boost gauge are you reading this on?

 

You didn't say it wasn't your car, I'm betting we all figured it was (I know I did). Now that that's known, you may want to insist on performing a compression test yourself on the motor before buying. Unless the price is low enough that it makes little difference to you if it should be rebuilt soon or not. My TII had moderately low compression when I bought it, but I only paid $1300. The motor locked up about a 1.5 years after I bought it, but I knew it was coming and I'd already gathered damn near everything I needed to port it and rebuild.