Freshly Rebuilt 1G Having Issues.

[DallasN2O]

1990 Laser RS-T 106,000 miles.. 330 miles on the newly rebuilt motor. (stock rebuild)

I have stock fuel system.. no afc.
Solid Upper IC pipe.
2G pistons, 1G rods
Stock Exhaust.
KN Filter mod.
Boost Gauge.
NO boost controller of any kind. Car is 95% stock.
Stock BOV, Stock IC piping etc.

I've been in the break-in period on this motor, was running fine after getting it out of shop. The other day I parked the car and went in the store for about an hour.. came back out and cranked the car. After leaving the parking lot I noticed that as I got on it a little the boost was going up too high. The boost was pegging past 20psi!!

After trying to figure out what was going on for a while.. I just went and parked it at home and left it overnite. A couple days later I get back in and the car is doing the same thing.. making crazy amounts of boost.. like the wastegate is stuck or something. Well after driving it for a while.. I think whatever it was that was stuck came unstuck. Ok now It boosts to 10 psi max but its running like absolute shit.

I can hear the turbo spool up and with the windows down I can hear it hissing very loud almost like a diesel truck whistles and it wont go past about 3600 rpm. At 3500-3600 rpm its stuttering and bucking and the boost is jumping between 5-10psi. I made a log of this tonite:

3rd gear pull:
RPM O2V TIM KNOCK TPS
-----------------------
1537 .74 17 0 100
1568 .74 16 0 100
1693 .75 16 0 100
1725 .75 17 0 100
1788 .77 15 0 100
1819 .77 14 0 100
1882 .77 15 0 100
1913 .77 14 0 100
1976 .77 13 0 100
2007 .77 13 0 100
2070 .77 12 0 100
2164 .77 12 0 100
2258 .77 12 0 100
2321 .77 11 0 100
2384 .77 11 0 100
2478 .77 12 0 100
2509 .75 12 0 100
2635 .75 12 0 100
2603 .75 13 0 100
2666 .75 13 0 100
2697 .77 13 0 100
2760 .75 14 0 100
2854 .75 14 0 100
2760 .75 14 0 100
2697 .75 13 0 100
2854 .75 14 0 100
3011 .74 14 0 100
3137 .74 15 0 100
2980 .75 16 0 100
2854 .75 16 0 100
2791 .75 15 0 100
2697 .75 14 0 100
2948 .75 14 0 100
3199 .74 14 0 100
3199 .74 16 0 100
3231 .74 16 0 100
3168 .74 16 0 100
3074 .74 15 0 100
3137 .74 15 0 100
3137 .71 16 0 100
3105 .74 16 0 100
3262 .74 16 0 100
3293 .71 16 0 100
3450 .74 17 0 100
3262 .69 16 0 100
3293 .71 15 0 100
3513 .74 16 0 100
3482 .74 15 0 100
3701 .74 16 0 100
3450 .71 16 0 100
3387 .74 16 0 100
3293 .65 16 0 100
3419 .56 18 0 100
3450 .74 17 0 100
3576 .71 17 0 100
3607 .74 17 0 100
3419 .74 17 0 100
3544 .69 17 0 100
3513 .43 18 0 100

Almost feels like a rev limiter or something. There is no smoke coming out of the exhaust. It idles at about 900-1000 rpm at making 20-22 Hg of Vacuum. There is no check engine light. Please help.

 

[DallasN2O]

Anyone?

 

[805DSM]

check if the wastegate actuator is conected ..sometimes the pin falls out and the actuator pops out and the boost starts getting all crazy..

 

[RipperXX]

Hmm strange, sounds like your waste gate wasn't opening causeing the high boost. At first I was thinking that maybe the higher boost caused some new leaks, but as good as your vacume is it doesn't sound like thats the case.

My sudjestion is to just go over the whole turbo/forced induction system and look for a problem.

 

[DallasN2O]

What would cause the car to not go past 3500 rpm? Arent those O2 voltages way wrong?

 

[Dsm2nr89]

It could also be a vacuum leak.A friend of mine has a 99 GS 5-speed that had missing vaccum lines and wouldn't let the car go past a certain rpm point.Forgot what rpm,but that could possibly be to blame too

 

[DallasN2O]

I do hear an unusual amount of hissing while its boosting.. like a whistle. But at idle its making good vacuum and I'm not getting any idle surge.

 

[Dsm2nr89]

That's weird then..But aren't turbos supposed to whistle when spooling ? But if its an unusual whistle then i dont know.

 

[Rob10_99]

did you do a boost leak test yet?

 

[DallasN2O]

No I figured if it was making good vacuum and not idle surging that it wasnt a boost/vac leak.. am I wrong in that assumption?

 

[Marc91GSX]

No I figured if it was making good vacuum and not idle surging that it wasnt a boost/vac leak.. am I wrong in that assumption?

Yes, you are wrong in that assumption. Under pressure your piping and connectors will swell causing a leak that you can not notice at an idle under vaccuum. You need to do a boost leak check to be sure that you are not experiencing a leak under pressure.

I am having a similar problem with my car and I have yet to be able to determine what is causing mine. Do to circumstances beyond my control I have not been able to work on my car for a long time but hopefully you get yours resolved soon. I may even be able to use this thread a source of help. You can also search for some of my old threads on here describing my problems and see if any of the tips I received will help you.

 

[phillip]

You probably blew your pipin from boostin 20psi, i've done it lots of times. check wastegate, it's ethier stuck or your arm is not hookdup.

 

[DallasN2O]

Makes sense.. I will check that. That is very possible becaues of the increase in boost pressure I was getting. Could have blown a hose connector loose or something. How could I check to see why or if the wastegate is the cause of the unlimited boost?

 

[ThingyNess]

Most common problem with wastegate failure is the diaphragm developing a hole and then not holding vac/boost. Take off the vacuum line that's attached to the wastegate actuator and leave one end connected to the actuator canister, and if you have an air compressor, set the regulator to 15psi or so and use a blowgun to pressurize the diaphragm in the actuator. If it doesn't hold the air pressure, or doesn't open the wastegate (you'll be able to see the actuator rod move), then the diaphragm is bad and you'll have to replace it. Otherwise, make sure the vacuum line itself is in good shape and connected to the compressor outlet pipe nipple, and you should be good to go. Without an MBC, there aren't really any other things to go wrong with respect to overboosting.

 

[SoonToBeDSM06]

If I'm not mistaken if the rod wasn't connected to the wastegate flapper then wouldn't it not make boost at all? The flapper wouldn't have any pressure against the exhaust if the rod wasn't connected and would blow open right away. With the boost spiking to 20+ psi, there might be a leak between your boost source and your wastegate. Also check your MBC if you have one and make sure its installed right. And like Thingy said, check the wastegate diaphragm for leaks with an air compressor.

 

[DallasN2O]

He was right.. boost leak.