North American Turbocoupe Organization



Low boost
Shelbycobra Offline
Junior Member
#1
Hello,
I’m new to the group.  I just bought an 88 TC and it’s not producing much boost and we think it may be the wastegate.  I have not been able to find parts and I was hoping for some recommendations.
Thanks!
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Kuch Offline
Senior Member
#2
Shelby,
welcome to the group, you will find a lot of great help on here, as I did. My 88 TC had a similar issue when I got it, and it was the wastegate, but not how you think. To trouble shoot, I put it up on ramps, hooked an air line to the wastegate input and turned my compressor regulator down to 15 psi. I then applied the low air pressure to the wastegate to watch the movement, it did not move. At first I thought it was a bad diaphragm and as I went to remove it I found that the control arm itself was kind if semi welded to the wastegate puck arm and holding it semi open. This was basically building slow and low boost. I am not sure why it was stuck so solid together like that, but it was. Once I got it broken apart and moving freely, went right to 18 fast psi with a Gillis. You should put yours on ramps and try watching the movement of the gate.
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4, ported E6, 255LPH, Kirban, Stinger Exhaust, MGW shifter, K&N, Gillis valve, BP1.5, PIMPx, Koni's
1964 Ford Galaxie 500XL, 390 6V, Big Solid cam, Headers,3.89's, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 312 4bbl intake, headers, 3 Speed, slow and low
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Shelbycobra Offline
Junior Member
#3
(07-30-2020, 07:51 PM)Kuch Wrote: Shelby,
welcome to the group, you will find a lot of great help on here, as I did. My 88 TC had a similar issue when I got it, and it was the wastegate, but not how you think. To trouble shoot, I put it up on ramps, hooked an air line to the wastegate input and turned my compressor regulator down to 15 psi. I then applied the low air pressure to the wastegate to watch the movement, it did not move. At first I thought it was a bad diaphragm and as I went to remove it I found that the control arm itself was kind if semi welded to the wastegate puck arm and holding it semi open. This was basically building slow and low boost. I am not sure why it was stuck so solid together like that, but it was. Once I got it broken apart and moving freely, went right to 18 fast psi with a Gillis. You should put yours on ramps and try watching the movement of the gate.
Thanks for the reply Kuch, I appreciate any help we can get!  We tried putting a little bracelet like chain around the wastegate to try to hold it shut and it broke the little chain so we know the gate is moving.  We then put zip ties around the gate and we got boost up to 10.  Do you think that means the actuator is shot?  We will have to try your suggestion to see what it does.
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Kuch Offline
Senior Member
#4
I would try it with air pressure to see how it moves. Using air pressure simulates the actual way it operates, so you should be able to see it move as well as look for leaks in the diaphragm. If you have one of those small vacuum pumps you could also try a small vacuum on the diaphragm and see if it holds. You could also try disconnecting the air line coming from the turbo and drive it like that, the boost should build to max what the turbo can put out, so drive carefully like that. with it disconnected, you are letting it build its max pressure regadless of the wastegate actuator. Let us know what you find next.
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4, ported E6, 255LPH, Kirban, Stinger Exhaust, MGW shifter, K&N, Gillis valve, BP1.5, PIMPx, Koni's
1964 Ford Galaxie 500XL, 390 6V, Big Solid cam, Headers,3.89's, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 312 4bbl intake, headers, 3 Speed, slow and low
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Shelbycobra Offline
Junior Member
#5
Even with air lines off we still had to keep the wastegate ziptied to produce 10 or 11 psi, that’s all it would generate.
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Kuch Offline
Senior Member
#6
so yes, it sounds like your wastegate actuator is bad. I have an actuator off of my 88 if you want it, just cover shipping. I pulled my IHI to put on a T3/T4 so I have no need for it. Let me know.
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4, ported E6, 255LPH, Kirban, Stinger Exhaust, MGW shifter, K&N, Gillis valve, BP1.5, PIMPx, Koni's
1964 Ford Galaxie 500XL, 390 6V, Big Solid cam, Headers,3.89's, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 312 4bbl intake, headers, 3 Speed, slow and low
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Shelbycobra Offline
Junior Member
#7
Sorry I didn’t get back to you!  Strangely enough the more we ran it the better it got and one day it suddenly would peg the needle so we had to be careful.  We took the zip ties off and it still worked but then we hooked up the air lines again and it would only produce 10 pounds.  Now we are trying to diagnose that issue.  
Thank you so much for the offer on the wastegate, I will definitely keep it in mind.
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Jeff K Offline
Administrator
#8
Manual or auto tranny? Auto tranny cars are limited to 9 to 10 psi under all conditions in an attempt to keep the weak A4LD tranny alive. 5 speeds should hit 14 psi under some conditions determined by the PCM via the BCS (boost control solenoid). The stock 5 speed BCS system sucks. Most of us use adjustable pressure relief valves (Google "gillis valve") to set max boost to whatever we want, typically 15 to 17 psi. The actual BCS valve on the pass side fender is a cheap plastic POS that can and does fail limiting boost to 9 to 10 psi under all conditions. If its electrical connector is unplugged or the valve itself has failed,or the valves vac lines are messed up, max boost will be 9 to 10 psi under all conditions.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Shelbycobra Offline
Junior Member
#9
Thanks Jeff! It is a manual so it should be higher. I will check out the Gillis valve.
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