North American Turbocoupe Organization



Confusing Lack of Boost...
DMC24guy Offline
Junior Member
#1
Ok, I've got an 87 Turbo Coupe with an Automatic. Knowing that, you would assume that I would be getting about 10psi of boost. I'm not.

For the past 6 months that I've owned this car, I've gotten at Most 6psi.

I've checked all the hoses, and none appear cracked. The IC hoses are not split, and all the Clamps are tight.

Two days ago I had a new Catalytic converter installed, but that did not change anything.

Today, I spliced together the two hoses that go the the BCS and the net gain of boost was a whopping 1psi!

I am left thinking that either:

A)The car has 200+k miles on it, and the turbo needs to be replaced

B)The Wastegate has some sort of problem which I don't know how to diagnose

or

C) I've been getting 10psi this whole time, but the stock gauge isn't reading correctly for some reason.

I'm leaning towards (B) simply because everyone seems to point to that as being the leading cause of boost lossage. Problem is, I have no idea how to check it and It's in a very awkward area to get to, and I really don't enjoy those 2nd degree burns from the exhaust.

Any other ideas? Suggestions on how to check the Wastegate? Pictures?

Thanks
1987 Ford Thunderbird Turbo Coupe....AKA..." The Black Bird "
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Pete D Offline
Administrator
#2
I vote for C, inaccuracy is not uncommon

or D, boost leak

To check B, apply 9.5 to 10 psi to the waste gate actuator port and watch the actuator rod. It should barely move, just a few thousandths of an inch. It it moves a lot then the spring in the diaphragm is weak, allowing the WGA to open the WG below 9.5 psi
Pete Dunham


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DMC24guy Offline
Junior Member
#3
I apologize, but I...am an idiot. Where is the Waste Gate Actuator port? Is it easily accessed? And is this rod on the top or bottom of the WGA?

I purchased an Aftermarket Boost/Vacuum Gauge yesterday, so hopefully in a few days I can rule out a faulty gauge.

Also, where would I check for a Boost Leak? Like I said, all the lines appear to be good, no cracks.
1987 Ford Thunderbird Turbo Coupe....AKA..." The Black Bird "
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Ballman Offline
Senior Member
#4
My guess is A , thats alot of miles and 2 your in Az. where its really hot and Turbo and heat and alot of miles tells me , change that Turbo unit , sometimes you can get the whole unit with the waste gate . Not that hard to do , most of the time I take off the exhaust manifold with the whole unit still on it , then take it apart on the garage bench . That way its easy to get to those old bolts or can deal with any other thing that may come up . Hope this helps ya , SCya, DW
DW
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Joe F Offline
Posting Freak
#5
The waste gate actuator (a vacuum diaphram-looking thingie Big Grin ) port is on the front of the wastegate, between the turbo and the exhaust manifold; it's a rubber pressure/vacuum hose.

The rod that physically actuates the the turbo wastegate is located on the opposite side (rear) of the actuator and is physically connected to the wastegate arm on the turbo exhaust housing.

Boost leaks can occur at any vacuum hose that "sees" boost; can also be at the intake. Many times the leaks are difficult to impossible to find by physical inspection alone.

HTH
JR's Place - My '87 Turbocoupe
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Pete D Offline
Administrator
#6
This may help http://natomessageboard.com/uploads/0000...tated1.JPG
Pete Dunham


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BJ SIMMERS Offline
Junior Member
#7
I've got a similar problem, but my 87 tc gets boost most of the time, but every once and a while it misses boost. I'm confused also.
I'd rather be hated for what I am, than to be loved for what I am not.
rides: 87 TC, 90 vw jetta 1.8l, 98 vw jetta 2.0l, 97 ford f250 crew cab 460ci, 85 bronco 351 ci, 66 merc. comet cyclone gt beefed 289, 94 hd sportster 1200cc, 97 thunderbird 3.8l
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Pete D Offline
Administrator
#8
BJ, any pattern to when it misses. Example, does it miss boost after the car was full boosted?
Pete Dunham


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BJ SIMMERS Offline
Junior Member
#9
no, it just decides not to boost sometimes. Like when I'm driving normally and decide to get into the throttle, sometimes it just doesn't boost like it should. I've checked all vacuum lines, had a crack in the one so I fixed that and still nothing changed.
I'd rather be hated for what I am, than to be loved for what I am not.
rides: 87 TC, 90 vw jetta 1.8l, 98 vw jetta 2.0l, 97 ford f250 crew cab 460ci, 85 bronco 351 ci, 66 merc. comet cyclone gt beefed 289, 94 hd sportster 1200cc, 97 thunderbird 3.8l
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Pete D Offline
Administrator
#10
Have you checked the turbo shaft for side and end play?
Pete Dunham


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