New gn, overboost, tcc lockup....

Turboteig

New Member
Joined
Mar 14, 2009
Hi, just got a new 87 gn. The problem I am having is when i mash the gas, when the boost gauge gets up to 15 psi the (i think) fuel cutoff is comeing on, I assume its overboosting, trying to figure out why. The wastegate vacuum hose goes into the t, and then goes into the solenoid.....The wastegate can be turned by hand if you pull on it, so it is free.....

That does sound like what the problem is right? It just cuts out completely for a second over and over like a rev limiter.

So we just need to figure out whats the cause of the overboost.




Also, for some reason the tcc was staying locked. It DID unlock in 1st which tells me the solonoid itself is not stuck on. Brake pedal did not unlock it either, so im guessing it was grounding out or the ecm was commanding power to it..... Any common problems there? Did it once....
 
EDIT - hooked turbo vacuum hose right to the wastegate and it limits boost!! doesnt cutout. Gauge goes to about 13 ish??

SO that means the boost solonoid is bad then right??
 
You have a bad TCC solenoid. The transmissions are designed so they cannot lock in first gear.
 
If i'm not mistaken there is a first gear override switch for the tcc therefor if the solenoid was jammed on it would kill it in first gear, thus meaning that this is an electrical issue, not the solenoid itself. No?
 
There is no fluid path to the solenoid in 1st gear, physically impossible for it to lock. As soon as it hit second though.....
 
If i'm not mistaken there is a first gear override switch for the tcc therefor if the solenoid was jammed on it would kill it in first gear, thus meaning that this is an electrical issue, not the solenoid itself. No?

It is not an electrical issue. The transmission is designed so there is no hydraulic path to lock the converter in first gear. This is a safety feature so it will not stall the motor when the car comes to a stop if the solenoid fails.
 
ok great, thanks. Now for the overboost, since the wastegate's vacuum is hooked to the turbo nipple and the wastegate actually functions now, that means its the boost solenoid?
 
Is it hooked to the correct nipple on the solenoid? The other side is the breather. I got rid of mine years ago, just use a grainger valve (brass with a ball/spring) and your wastegate.
 
Is it hooked to the correct nipple on the solenoid? The other side is the breather. I got rid of mine years ago, just use a grainger valve (brass with a ball/spring) and your wastegate.

If I'm remembering correctly, it doesn't matter which side you hook up to........
 
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