Overboost

[Guest]

I have a bad (well, rather my TGP) case of overboost, or at least that is what it appears to be.

Can someone give me a good indication of what the pressure/vacuum should be on the line to the Wastegate actuator? I have searched the boards and sites and don't see any acutal psi value!

I suspect that either I have a bad controller valve, or a bad actuator, but am trying to determine which. It is really hard to observe what the f.... is going on under the hood, when the problem only shows on harder accelleration. It pegs the boost guage at between 1/2 ahd 3/4 trottle, so I think I deffinately have a problem, and WOT gives a definite cut in power, like it is cutting timing. I don't get a code set, so it is not severe, but is definately a problem.

I have checked fuel pressures, they appear to be good at idle and with a restriction in the return it climbs so believe that not to be fuel starvation.

Any very specific values on pressure would be helpful. Any other ideas would be welcome also. Thanks,

[eclipse5302]

1.Take a look at the tubing that comes from the lower output side of the turbo, to the solenoid on the intake manifold, then to the wastegate actuator. Make sure that is all intact, and not cracked or loose.

 

2.Then check the wiring to the wastegate solenoid (the part mounted to the intake manifold with the two small lines goin to it)...make sure it's not loose or missing.

 

3.Then try to move the wastegate actuator rod. It is supposed to move out of the actuator, and other than the spring tension that the actuator creates, it should move. You will probably need a pair of pliers or a screwdriver. Remember, you are trying to move it AWAY from the actuator, not towards it.

 

Jason

[Chris A]

Unless the solenoid melts down inside and blocks off the boost to the actuator, its failing can't cause and overboost. Its is activated to increase the boost level. If it is inactive, boost will be controlled by the spring pressure in the wastegate, which is about 4 psi. The psi going to the actuator varies on how much boost you are building, and how much boost the actuator is passing. There really isn't a spec on it.

 

If you are overboosting and shutting down, it could be the actuator failing. The best way to check that is with a Mighty Vac, or similar tool to apply pressure to the actuator and watch it open. If it doesn't open, then its bad. However, if you are running stock, and breaking up at boost it could be something else. You mentioned the boost guage pegs (paste 15?). If you are not running a chip, then its definitely overboosting as you should never see that much on a stock chip.

[Guest]

Did #'s 1, 2, and 3 in eclipse5302's post, and all are intact to the naked (well, as I get old I have to wear boosters, but as naked as eyeglasses can be) eye.

 

This guy has a TopGun160/K&N upgrade. The actuator appears functional, not frozen, and the lines are both intact and routed correctly. The wiring to the 'sloenoid' (I would call it a valve, but I am a data guy, not a professional wrencher) is good, so my guess would at this point be the solenoid is failing, but hard to get that by the description of the scenario you give.

 

Therefore, my next test was to 'T' the line to the actuator (I did this once, seems I saw ~7 #'s pressure there at WOT) and compare this to what a good one would be. Is that value what you would expect to see at this point?

 

Also, what does a normal chipped TGP show on the boost guage at WOT, mine exceeds 15 and goes into lazy dog mode , if I back out of the throttle, say to 1/2 or so, it will recover and run strong again. No codes are set indicating sever detonation, and like I said it appears fuel pressure is OK per a static idle test, so if I can't get any where down this line where next? I have considered a fuel pump swap to eliminate that but that is a lot of work if it is not the problem.

 

Any further help is appreciated.