Pontiac Sunbird Turbo questions

toofreds · Post by **toofreds** » Tue Oct 05, 2004 6:43 pm

My 1986 Pontiac Sunbird GT Turbo 1.8 is running great but ever since I had emergency repairs to the oil pump on the road it will not boost. It did not run short of oil at any time nor was it making any noise. The dealership was kind enough to replace the turbo unit anyway before the mechanic admitted he had never seen one before. Replacement did not help. I have good vacuum pressure in both ranges and have replaced the boost solonoid but that did not help either. The boost indicator in the dash rarely goes more than a whisker into the positive(+) range.
There were apparently only three of these built and I have two. (one for parts) There are no living mechanics in the Atlanta/Chattanooga who know anything about this system, much less enough to troubleshoot, and it rarely appears in fixit manuals. I have sent so many emails asking for help without reply that I thought my email was broken. Please help me!!!
Where does the signal that activates the solonoid originate and how does it know when the time is right?
TooFreds

Post by **PrecisionBoost** » Thu Oct 07, 2004 5:15 am

Hmmm.... I have an 87 Sunbird GT Turbo with the 2.0L but I belive the two engines are nearly identical. ( just as the 1.8L Lacetti engine is nearly identical to my 2.0L Optra engine)

So you are saying that they replaced the turbo and it didn't help?

Did they replace the waste gate actuator on the turbo??

I'm not sure what you are calling the boost solinoid..... perhaps this is the waste gate actuator.

The "signal" for the waste gate actuator comes from the intake manifold.

As the car goes up in RPM the turbine side of the turbo has more exhaust flowing through it so it picks up speed which turns the compressor side faster.

The compressor is the side that suck air from the intake and pushes it into your engine.

So as boost starts to build to the factory cut off ( 7psi ??? ) the waste gate actuator starts to pull back a flap inside the turbo which allows some of the exhaust to go around and bypass the turbo.

Without the waste gate actuator the boost would go way past 7psi and boom your engine would die.

The only way that the actuator can pull open the gate is if there is pressure built up in your intake.

So if the line from the intake wasn't there your boost would probably head towards 12-14psi and then the ECU would shut your car down to try and save things ( but you can still damage your engine )

The wierd thing is that you say it doesn't even go positive.... so there is no way that it's an issue of the waste gate opening too early (unless it's very heavily damaged)

It sounds to me like you should get someone to test your turbo....and inspect all the parts ( especially the waste gate )

You might find cracks around the waste gate but this is quite normal for these turbos, I have two of them and both have cracks.... one small one large.

Even with the large crack it didn't affect the boost much.... it still ran about 6-7psi.

Hopefully someone else can come up with some ideas because this sounds really strange to me... it doesn't make sense if you replaced everything and it's still not working.

GsiTurbo · Post by **GsiTurbo** » Thu Oct 07, 2004 5:31 am

This topic has been split from the original post HERE, and its also being continued here: http://www.daewootech.com/forum/viewtopic.php?t=1631

daewooluvr · Post by **daewooluvr** » Thu Oct 07, 2004 12:57 pm

if all else fails, ask on www.turboforum.net
They're a good group of guys that I've learned quite a bit from.

richardmatalon · Post by **richardmatalon** » Sat Oct 09, 2004 10:50 pm

You have one of maybe two probelms there. The first being as erfinder said there is a problem with the wastegate, mabe it is stuck in the open position, this could be that the actuator is not functioning properly and has the rod extended all the way or maybe the wategate is stuck in the open position and the constant heat has almost welded it that way. The second possibility is that there could be a leak some where in the hoses from the trubo to the intake manifiold or on the manifold it self. YOu would know if this is the case becuase you would hear it , you would hear the turo loud, the same noise that you would get when you are boosting, you would hear it very loud, becuase the air is leaking out. SO I would check all of the hoses to the intake manifold, from the compressor side of the turbo(the one that is silver becuas eit is aluminum) and that should solve oyur problem, or atleast point to you where the problem is