This is driving me nuts

[boosted231]

I can't get my car to boost over 5lbs. I'm not sure what else to check. I have an 87 gn with Walboro fuel pump, hot wired, adj fuel pressure reg., ATR 2.5inch exhaust,and a big neck stock intercooler everything else is stock. I couldn't get this thing to boost over 5lbs. So I changed the boost solenoid, y hose to the solenoid and put an adjustable wastegate on with no change. Someone had suggested to me that my cat might be clogged up so I just put a THDP and a high flow cat on again no change. I checked all the hoses on the intercooler and up pipe all tight. I tried to adjust the wastegate and again no change. The car spools slow but runs smooth. I just finished a new timing chain, waterpump and new front and rear main seals but the car runs the same now as before I did that work on it. Something else that the car started doing is the factory tach shoots all the way up in the red and doesn't move when I start and drive the car. If anyone could steer me in the right direction I would appreciate it. Thanks Also I do have an aftermarket boost gauge.

 

[equalizer442]

it could be a bad ecu

 

[boosted231]

I thought about that any other opions

 

[Lee_Burough]

Have you double checked the "Y" fitting installation?

Just a WAG....Is the "Y" fitting installed correctly?

Go Hereto see how it should be instlled

 

[JToups386]

Originally posted by boosted231
I can't get my car to boost over 5lbs. So I changed the boost solenoid, y hose to the solenoid...

You revealed the mystery in your original post. I'd bet my left "doo-dad" that it's the Y fitting. I did this a few years ago too. The Y fitting actually has an air metering valve in one side, and if you reverse the two lines, bingo, little or no boost!

Go swap it around, and report back to us. I bet you'll have fixed it with that!

If it's not, I'll be real curious to see what you find.

And, just to be sure, please make sure your actuator bar to the wastegate puck is still hooked on. If it came loose, the thing won't boost either. However, I'm assuming you would've noticed that...?

 

[2QUIK6]

Concering the "y" fitting, the straight part should connect directly to the turbo, the branching off part goes to the wastegate accuator.
To make sure you don't have a bad spring in the accuator, you can try it "tuner style" which will eliminate the ECM and wg solenoid, and Y fitting as a possible cause...Just connect a hose from the turbo to the accuator...spoolup will be very slow, and the max boost will be whatever the tension is on the spring, and will depend on how short you have made your adjustable arm, but you should see at least 10#s or so that way, if not, shorten the arm a little more.
If you can't get anymore boost this way, then it may be the accuator or the puck is not fitting right on the exhaust hole on the exhaust side of the turbo, thus letting out all of the exhaust gas instead of propelling the turbo.

you should be able to feel some tension as your putting the arm back on the wg puck arm, you should have to "Stretch" the arm/spring just a bit to get it on the wg puck arm.

 

[boosted231]

The Y hose is installed correctly. The only reason I replaced it is it was dry rotted in a couple spots. This whole thing started when the car backfired on me under boost, since then no more than 5lbs I must be overlooking something. The car runs smooth no problems starting or driving just won't boost up.

 

[boosted231]

Also there was no difference between the way the car ran with the stock elbow and the THDP.

 

[JToups386]

Any other vacuum leak possibilities?
Any oil in the up-pipe going to the TB?
Any play in the turbo shaft? Front to back, or side to side?

If everything was working correctly, you should see a little difference with the THDP. We don't spend $400 just to say we've got a big pipe...
The THDP has a much larger wastegate puck than a stock elbow, so it should definitely cover the hole. However, check to make sure it's not somehow stuck and unable to close completely over the hole.
You can take the DP loose, and spread some wheel grease, or vaseline, etc, around the puck. Then bolt it back down tightly, pull the puck lever shut against the turbo exhaust housing, and then take the DP loose again to see if there's a grease print completely around the hole. If not, you're not going to see full boost, per the leak.

 

[Hawaiian Turbo]

I noticed you said after the backfire, you checked the hose clamps, but how about for rips in the IC hoses? Only coming apart under boost.

 

[John Larkin]

Yeah, IC hoses. I had one slip on the compressor housing and it limited me to 20psi. Secured it and wham, to the moon Alice! Had to push back on the IC while tightening; I have a big neck on my IC also.

 

[UNGN]

Also check the "check valves" in the vacuum lines.

hows the crossover pipe and the headers? has the turbo been removed for any reason?

Could the backfire have been an exhaust gastket blowing out under boost?

For the tach... is it plugged into the fuel pump test wire?

 

[boosted231]

The reason I bought the THDP is someone suggested that my cat might be clogged so I thought if I was going to buy a cat I might as well go all the way. The drivers side header has a leak but it leaked before I had this problem. The crossover pipe is sealed and in good shape. I will take the IC and up pipe hoses off again and inspect to see if there are any rips. The turbo had a little play side to side. I'm not sure what the tach is plugged into I have never touched it.

 

[UNGN]

Originally posted by boosted231
I'm not sure what the tach is plugged into I have never touched it.

There should be two connectors behind the alternator. One is a fuel pump test lead, the other is a tach lead. They are not supposed to plugged into each other.

Many people assume the two should be plugged together and then the tach doesn't work.

If the headers cracked, Fix it, first.

 

[moose]

Maybe a possible bad actuator?

 

[boosted231]

I had the stock wastegate on the car when the problem started then bought an adjustable wastegate and put that on with no change. I will go ahead and fix the header but I don't think thats my problem because it has always had a leak between 3 and 5 and I know that doesn't help matters any. Thanks

 

[suprbuick7]

Hey Boosted,
I had similar problem. Mine turned out to be a "crushed " 14" K&N cone. Changed the cone and the boost went up

 

[2 SLOW]

I feel for you. I , like a lot of other people have had problems drive us nuts. It looks like you are looking for any shot in the dark, so I'll give you my shot in the dark.

I backfired one time and blew off IC hoses. Hooked them back up and still didn't run right. Checked the MAF and the pop also blew off the screen in the MAF ( I had already removed one). It will run with no screen but can screw up the way it runs bigtime. It's worth a check if you haven't already. If it pops hard enough to blow off IC hoses it can also blow back through the turbo to the air cleaner. Trust me mine did so hard it bent the screen!


HTH