2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

Cannot build boost pressure.

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Old Mar 5, 2012 | 11:51 AM
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Cannot build boost pressure.

I'm currently experiencing no boost. I was experiencing no boost with my stock ecu, and still currently experiencing no boost with my microtech.

The problem first occured when I swapped injectors. So i'm guessing the problem is related to the removal of the upper intake manifold and the areas around it.

All vacuum lines are in place, boost gauge reads vacuum pressure at around -20.

My car will not build boost at all, it will drive fine, but at WOT it just falls on its face.
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Old Mar 5, 2012 | 12:36 PM
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whats going on?
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did you not bother to check the injectors?
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Old Mar 5, 2012 | 12:41 PM
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Injectors are seated properly.
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Old Mar 5, 2012 | 01:14 PM
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Did you check the functioning of the wastegate by applying air pressure to the actuator and seeing at what PSI it activates?
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Old Mar 5, 2012 | 01:44 PM
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From: Socal 626
^I will try that, I'm putting together a list of things to do/check on the weekend because I won't have time to diagnose anything until the weekend. This quarter is really packed for me.
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Old Mar 5, 2012 | 02:16 PM
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Fuel pump
Fuel pump sock
Fuel line
Fuel filter
Fuel pressure regulator

?
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Old Mar 5, 2012 | 02:44 PM
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Boost presuure test the whole system FIRST. i beleive we went over this in your other thread (maybe not, someone else). This would eliminate 75% of your questions. If something leaks fix it. If nothing leaks, ckeck the wastegate. FIRST thing i would do is check the wastegate and see if the actuator rod is still hooked up to the flapper. If it is still hooked up, slowly slide the rod off and see if the flapper is hanging open. This may sound a little "rough" but once you see/do it its not. If you follow these steps, in about an hour you should be able to narrow down 99% of your options.
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Old Mar 5, 2012 | 06:05 PM
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^Yeah, I'm going to do that this weekend. Thanks for the help!

I'll post my results this weekend. Keep the suggestions coming!
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Old Mar 5, 2012 | 06:36 PM
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Checked the turbo for shaft play? Mine died somewhere between putting it up on jackstands and driving around the block after I finished some repairs.
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Old Mar 7, 2012 | 09:19 PM
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In for info. Mine is doing the same thing. Starts up, revs, but no boost is built.
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Old Mar 7, 2012 | 10:00 PM
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secondary injector being bad will do this.
bad air filter will do this as well.
exhaust leak will do this.
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Old Mar 7, 2012 | 10:38 PM
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Originally Posted by Hayseed7
In for info. Mine is doing the same thing. Starts up, revs, but no boost is built.
starts and revs...as in sitting in the driveway? or driving down the road?
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Old Mar 7, 2012 | 11:01 PM
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I haven't driven it, I figured i'd rather drive it whenever its running correctly than drive it when it obviously will not build boost.
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Old Mar 7, 2012 | 11:17 PM
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^ lol

Last edited by barkz; Mar 7, 2012 at 11:19 PM.
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Old Mar 7, 2012 | 11:30 PM
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Its not my daily, so I figured I'd get everything straightened out first.
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Old Mar 7, 2012 | 11:32 PM
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Originally Posted by Hayseed7
I haven't driven it, I figured i'd rather drive it whenever its running correctly than drive it when it obviously will not build boost.
so you are adamant about building boost in your driveway while the car is not moving?

Originally Posted by `iCED
Injectors are seated properly.

so you did not check the injectors (measure resistance across the pins) like you should?
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Old Mar 7, 2012 | 11:34 PM
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^ lol sounds like hes got the right idea... sell your car
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Old Mar 7, 2012 | 11:38 PM
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Ok, took the car around the block, same issues, you guys happy?
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Old Mar 8, 2012 | 09:10 AM
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^ no...
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Old Mar 8, 2012 | 09:33 AM
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The problem is that "not building boost" isnt descriptive enough of your problems.

can you free rev it to redline? [yes/no]?
when driving, and you floor it, does it hat a wall the moment boost tries to build?[yes\no]
when driving and you dont floor it, can you slowly bring it to redline?[yes/no]
is your intake filter clean?[yes\no]
are your spark plugs clean and new?[yes\no]
are your fuel injectors flow balanced and tested?[yes\no]


answer ALL of these questions and then get back to us.
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Old Mar 8, 2012 | 09:50 AM
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try spinning the turbo shaft by hand when it's cold and warm.


if it ran with the stock ECU then it couldn't have a massive leak, a wastegate stuck open would still give some boost. i suspect your turbo is crapping out.
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Old Mar 8, 2012 | 10:51 AM
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Originally Posted by Karack
try spinning the turbo shaft by hand when it's cold and warm.


if it ran with the stock ECU then it couldn't have a massive leak, a wastegate stuck open would still give some boost. i suspect your turbo is crapping out.
but if you read his original statement, he started to get problems after an injector swap.
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Old Mar 8, 2012 | 04:04 PM
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Originally Posted by SirCygnus
but if you read his original statement, he started to get problems after an injector swap.
Then he said he put everything back correctly. So where do you go from there? <-just a general observation, not directed at anyone really.

I'd start with the thing that makes boost. And checking for shaft play takes 2 minutes.
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Old Mar 8, 2012 | 05:04 PM
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pretty much, checking the turbo is much easier than testing injectors.
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Old Mar 8, 2012 | 06:59 PM
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i sort of have the same issue except my car builds boost. the boost guage goes up to maybe 3 psi? and it will rev to red line albeit has the 3800 rpm cut. it just feels like the car isnt going any where. the blow off valve blows off but the car feels almost na. im gonna try checking fuel filter and fuel pump, and gas tank because the car runs some what better not by much tho at the top end. it bucks quite a bit as well
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