low power

[jimcreek]

been having trouble with turbo waste gate soleniold (changed)I have good vacum at soleniold but none at waste gate.
checked fuse and voltage at soleniold (good).
checked ohms. from soleniold to ECM (good).
question 1. what tells ECM to activate waste gate solenoil.
Ihave noticed that ses light comes on at higher speeds (65 to 70 mph)when there for more than10 minutes.
code has something to do with fuel temputure.
any suggestions will help
95 gmc 3500hd no egr 100,000 miles engine

[patrick m.]

more than likely, there is a crack in the plastic vac tube from the solenoid to the actuator.
find a piece of hose, and two hose connectors to "jump" the two vac pipes together. then see if you still have no vac at actuator, if there is no vacume, trace the plastic tube to locate the crack.
good luck.

[rustypig]

What code # are you getting?

If it's #78 then a wastegate selenoid change is usually the fix. How many lbs hg (vacuume) are you getting to the selenoid?
Common problems with the system are generally: Rub through holes in the hard plastic lines to and from selenoid. Poor vacuume from the pump (should be in the 20+ range). Bad electrical connection at selenoid. Wastegate actuator stuck (not quite as common).

I do have the schematics for this around the house somewhere. Finding it may be the challenge of the day though.

What actually controls the boost selenoid? I can't say for sure, as I've never gotten that deep into the ECM, but from what I've seen the ECM can/will cut back boost/fuel when you've got hard load situations. ie...high fuel input/high egt condition w/high intake air temps. It seems the ECM was engineered to keep us from leaving expensive engine internals on the road behind us.

[jimcreek]

I have jumpered vacum acuator works truck runs better no more smoke what will it hurt to leave bypassed.
there was a code #78 waste gate soleniold I had already changed solenoild checked electrical wiring at soleniold. I beleive whatever tells ECM to make solenoild to work is bad although it maybe a combination of componts that tells ECM to activate soleniold.

[pannhead]

its no different than wiring the wastegate....good to get you home, but not a long time solution..good luck ;)

[JohnC]

One thing to check is if the vacuum connections are on the solenoid correctly. I recall the front-most barb is connected to the wastegate. In any case, the barb with the restriction in it is connected to the pump. Also, check the wiring harness, aspecially near the connector to the solenoid. They reportedly fail there more than infrequently.