Got this 87 Turbo T about 2 weeks ago and did some spring cleaning engine bay real dirty changed the single shot exhaust(dont ask why this guy did that) to a hooker 2 1/2 cat back no cat just test pipe. Car would take off the line then create boost quickly to 5 or 6 pounds then slowly creep up to about 15psi car sounds good until it spikes to 20 and detonates and sometimes missfires with ocassional backfire. Ithought it was exhaust work making more boost but I turned out wastegate rod until its ready to fall off and still making 15psi with an ocassional spike to 20.Doesnt happen all the time but when it does its very annoying when your trying to make a decent run with a vette.Anyone got any Ideas might be wastegate solonoid??stumped.
Look for leaks in the boost sense lines also check the orifice in the "Y" pipe in the sense lines. There was a series of these lines that were sold with an orifice that is too small.
Checked lines seems to have regular black t fitting goes from wastegate to sensor on top of pass side valve cover what sensor is this??
The GNTTYPE website has some very good articles on these cars. Have you checked those? Look for an article regarding sensor locations.
The lines are the boost lines. The sensor you're talking about is not a sensor. It is the wastegate solenoid which, in a round about way, controls the boost to a small degree.
You should not have a regular black "T" fitting in the line. You should have a "Y" fitting. In the proper "Y" fitting, there is an orifice and that orifice is of utmost importance. Just to be sure, purchase a new set of boost lines from one or our vendors. Just ask them to make sure they have the orifice for the '87 installed.
By the way, that sentence you wrote was a whopper!
Thanks Pat I cut out of English class in high school... Anyway ordered new adjustable wastegate and boost lines from Cottons. Took apart downpipe and elbow. Few questions on what I found, here goes.... Found that wastegate puck has some play I am assuming this is normal for a flush seat on turbo side? Compressor wheel now exposed seems to have a little play going in and out, normal??(maybe 1/16 inch play) Next,I am trying to understand how wastegate actually works, i thought when the wastegate starts to close this builds more boost? Then I figured out maybe that the more it opened it let more gases in to turn the compressor, can u set me straight on that one....Shaft had very litlle play going up and down but was still some there, concern??
No oil was found.When I do get new boost lines w on which side does orfice go I did have one but forgot to look before I took it apart, sorry for all the questions I will stop here before I become annoying. Thanks in advance..
Sorry also the wastegate solonoid has two vaccum ports on it but just one is being used to go to the wastegate?? Is this normal or did I pop one of the hoses off and dont know about it? Thanks
Solenoid - it works on pressure, not vacuum. I'll explain in a moment. The one port is supposed to have a foam air filter on it but it really doesn't matter. The solenoid is just a valve that pops open to bleed off pressure in the boost sense lines. If you are looking down on the solenoid valve and the connector is nearest you and the ports are away from you, the port that GM intended you to use is on the LH side (at least that is how mine is).
Next, check out http://www.gnttype.org/maint/quickref.html
Part way down is a picture of the "Y" pipe. When you receive the assembly from Jack, the lines will be of different lengths and shape and the "Y" will be connected to them. Once you lay the new assembly in place, it should become fairly obvious which ones go where. To answer your question directly, the leg of the "Y" that has the orifice goes toward the fitting on the compressor outlet.
Wastegate: As boost develops, pressure builds at the compressor outlet and air begins to flow into the "Y" through the orifice. The solenoid, in turn, is letting air out per computer commands. But, it doesn't let air out as fast as it is coming in so pressure builds in the boost lines. As the pressure builds, it forces the wastegate actuator to extend against the springs located internal to the wastegate actuator. Eventually, a happy middle ground will be reached between the boost pressure and the spring and boost will be constant. You have it nearly correct, the puck is closed when there is no boost, when you step on it :-), the puck opens and that controls the boost. The puck is on the hot side or turbine side of the turbo, the compressor side is the side where your air lines hook up.
It is very important that the boost sense lines are in excellent condition and remain attached to their fittings. A broken boost line or an orifice that is too small can quickly lead to overboost! Take the time to fasten tie wraps around the boost lines at the three locations to make double sure that those lines do not fall off.
I can' help with the end play on the turbo wheel, it doesn't sound too bad to me especially since you don't see any oil. Should be OK to go.
Do you have a boost gage that is not the stock one? Don't rely on the stock gage. My advice? Until you've got a reliable boost gage, once you install the new wastegate, adjust it so you have only a little spring tension to keep the wastegate valve closed. Maybe 1/16" extension to hook the rod to the lever of the puck at the most. You can always increase the boost later, it is harder to decrease it once the engine blows up.
Hope my long reply helps...let us know how you are doing.
Sounds good. I recieved the lines and actuator today and will install them tomorrow. By the way when looking down at the solonoid and the ports are away from me the right one has the vacumm line on it with no breather on left ill try to reverse it to see what diff it makes. Thanks for the info I will let you know what happens next..
I went to CaspersElectronics' website and looked at a photo of the solenoid. Your system is right, the vacuum line belongs on the RH port so don't change yours. I'll just reverse mine but I still don't think it matters.
Sorry for the confusion
no prob thanks gonna install tonight anyway I'll let you know if spike goes away.