Over Boosting!

[DAVID C]

I can't figure out why my '86 GN is running 20-21 pounds of boost on my stock GN. I've replaced the hoses to the wastegate, replaced and adjusted the wastegate, replaced the wastegate solenoid, and tried a different chip. The wastegate puck is good and free.
I'm forced to run around with a seperate gauge staring at me through the windshield so I don't get carried away and blow the motor up.
This is all stock except for a TH downpipe, MAF translator, and cold air kit. It's done this since I purchased the car (bone stock) last fall.
Could it be the MAP sensor? Any help would be appreciated.

 

[Just a Six??]

It could be the wastegate puck itself. If you look at it when apart how is the carbon line around the hole for the puck? I was getting spike until I ported the hole to match the puck size. Should be about 1/16th overlap from puck over hole. You will see the carbon ring.

 

[Roger]

I have the same issue, however, it only goes up to 17.5 & I'm living with about 2.0 kr. I also set the timing at 2* retard.

 

[1fast6]

What are the stock turbo's capable of? Could it be boost creep? Is this only happening at high rpm's?

 

[DAVID C]

It's not boost creep. It climbs right up mid way through 1st gear. I would think that a bad seal on the puck would cause low/slow boost. I thought maybe the Map sensor was giving the ECM a false reading, causing it to hold back on the wastegate solenoid opening.
When I get a chance, I'll try the MAP sensor from the wife's GN.

 

[notacarlo]

Is the little grey "Y" still in line with the actuator? Is it positioned in the correct direction?

 

[DAVID C]

Yes, the Y is there and positioned correctly.
This problem is getting my butt in gear to finish assembling my alky kit

 

[mikestertwo]

I'll try the MAP sensor from the wife's GN.

The MAP sensor has nothing to do with boost. The MAP just runs the boost gauge, nothing else. The computer actually has no idea how much boost the motor is making. It's just a calculation. Try plugging the line going to the boost solenoid and see how much boost it makes. Should be around 11psi. Did you try loosening the wastegate actuator to see what happens?

 

[Brady]

I had the same issue. I ran a good new hose ( its cheap) from the compressor straight to the actuator. it was still overboosting so i replaced the actuator and that brought the boost back to normal. Then I put the hose and tee back in like stock to the solenoid and overboost again, replaced soleniod and better! Beware that straight from the compressor to the actuator you will have to shorten the arm quite a bit to get in the teens for boost but when you put the solenoid back into the mix adjust the rod longer or you will overboost again.

 

[DAVID C]

I'll try plugging the solenoid hose. If that works, and I'm able to adjust the boost to where I want it by the rod adjustment, is it okay to keep running like that, or is there a down side to it?
I've backed the rod off to where there's barely any pressure on it and it's still running 20psi. Maybe both my (used) actuators are bad.

 

[Brady]

You can run it that way, the boost just builds a bit slower and you need to adjust the rod a bit shorter to get the desired boost. I ran it that way for a few months, but I got the replacement soleniod and put it back in and boost is quicker. I was also losing a bit of boost at the shifts without the solenoid. The solenoid is only $50 from a parts store.

Good luck

 

[Razor]

Keep running that boost on pump gas without alky or race gas and you'll be building a new motor pretty quick. As your detonating it.

Only a few parts responsible. hoses to turbo, actuator, Y fitting, WG solenoid, and downpipe. The downpipe can only be the issue if its sticking.

Run a hose from turbo to actuator, that will be minimum boost. If that works, your problem is Y, hoses, or solenoid.
If it doesnt work, its a bad actuator.

You can test the actuator apply compressed air.. it will extend and stay there as long as air is on the port.

WG solenoid is designed to bleed air. If the hose to it is plugged.. use a golf T.. it will be like hooking hose from comp to actuator.

 

[turbo nasty]

OP mentioned adjusting wastegate.

What wastgate do you have? HD?

 

[DAVID C]

I'm sure it's not the solenoid. I swapped with my wife's car and there was no difference. Her car has no issues. I didn't try mine on hers though. The actuator may be bad. The one I tried was in a pile of unknown used parts I purchased years ago. The hoses are all new. I'll put compressed air to the wastegate through my pressure regulator tomorrow and see what psi it opens at, if at all.

 

[NM Tom]

If you can "adjust" the rod it's not stock and most likely a heavy duty acuator and they are set for 20 pounds of boost before the acuator sping will begin to open. Go stock or use higher octane\alchy.

 

[DAVID C]

It's finally fixed. I can't believe I didn't find this sooner. I had replaced the hoses from the solenoid to the wastegate actuator and to the turbo.... All but that 2" hose between the solenoid and the plastic reducer/elbow. Low and behold, it had a 1/4" split in it. It wasn't noticeable until I pinched off the turbo line and put compressed air to it.
I just took it for a spin, and it's showing 14 pounds of boost. Thanks for all the help. Now that I have a solid baseline, I can start the modifications.

 

[Smokin-6]

Glad you figured it out. Now get Alky and turn up thr boost!:biggrin:

 

[nonova0074]

thanks for the thread helped me out