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87 Sprint Turbo - Overboost or Fuel Cut in high RPM + CEL
http://www.teamswift.net/viewtopic.php?f=22&t=62171
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Author:  fxyxixe [ Tue Dec 06, 2016 9:33 pm ]
Post subject:  87 Sprint Turbo - Overboost or Fuel Cut in high RPM + CEL

Hey all,

I just picked up a very good condition Sprint Turbo. It drives beautifully besides have an issue at high RPM.

Essentially, when you're "in it" in 2nd/3rd/4th/5th, it will start to immediately dump boost(BOV/Recirc valve is doing its thing) mid-throttle. This is accompanied by a CEL which then goes away.

To me, this sounds like classic overboost/fuel cut but it seems odd. A lot of the parts on the car have been replaced/repaired in the past 5-6 years and I haven't dove into it yet.

I haven't been able to narrow it down to anything and before I instill any sort of ideas into your mind - what could it potentially be?

It drives, idles, revs and shifts smoothly otherwise. No problem if you're 1/4 or 1/2 throttle.

Thanks!

Author:  jaguar,vettes&sprints [ Wed Dec 07, 2016 12:08 am ]
Post subject:  Re: 87 Sprint Turbo - Overboost or Fuel Cut in high RPM + CE

welcome to teamswift
Is your wastegate hose In tack if that little hose is broken or missing a modified it will overboost and cel will come on and ECM will limit fuel/spark
get a boost gage $12 and tell what your boost is do'in
I liked around 11lb of boost you could run 15lb with mods....jv&s
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Author:  suprf1y [ Wed Dec 07, 2016 12:37 am ]
Post subject:  Re: 87 Sprint Turbo - Overboost or Fuel Cut in high RPM + CE

Stuck waste gate is common in cars that have sat for a while

Author:  fxyxixe [ Wed Dec 07, 2016 10:29 am ]
Post subject:  Re: 87 Sprint Turbo - Overboost or Fuel Cut in high RPM + CE

Thanks gents, will check that out. It hasn't really sat - PO was driving it everyday just very briefly. Probably not much boost.

Anyone have a how-to for the boost gauge for this car? I know how to do a boost gauge but maybe there's some hints on mounting and routing for this car :)

Author:  t3 ragtop [ Wed Dec 07, 2016 4:54 pm ]
Post subject:  Re: 87 Sprint Turbo - Overboost or Fuel Cut in high RPM + CE

i'm a fan of electronic vacuum/ boost gauges that mount a pressure sensor under the hood near the intake manifold and carry the electrical signal into the cabin via wiring. my favorite gauge is made by cyberdyne and it isn't all that expensive. it has a black out face and comes with auto dimming red, green, or blue led readouts.

there are several ports located at the rear of the intake manifold, some with pipe plugs in them from the factory. i drill the center most port, tap it for 1/8" npt, and use a barbed hose bib for the hose between the manifold and pressure sensor.

Author:  jaguar,vettes&sprints [ Wed Dec 07, 2016 10:25 pm ]
Post subject:  Re: 87 Sprint Turbo - Overboost or Fuel Cut in high RPM + CE

put a TEE in this line for your Boost gauge stock boost is 7-8 Lb
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This will work what I used
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https://www.amazon.com/Autometer-5701-B ... ntom+boost
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Will work
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https://www.summitracing.com/parts/equ- ... oCf07w_wcB
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Cheep will also work
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http://www.ebay.com/itm/Turbo-Boost-Vac ... rp&vxp=mtr
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Author:  fxyxixe [ Fri Dec 09, 2016 1:09 am ]
Post subject:  Re: 87 Sprint Turbo - Overboost or Fuel Cut in high RPM + CE

Thanks guys!

Also, new development, it always happens between 3,500 and 4,000 rpm.

Author:  fxyxixe [ Sun Dec 11, 2016 6:16 pm ]
Post subject:  Re: 87 Sprint Turbo - Overboost or Fuel Cut in high RPM + CE

For those keeping up - I found the wastegate to be pretty crusty and not moveable by hand(using a bad angle not removing anything besides the IC hose and plug wire).

So if it's stuck, could that be my 3500rpm problem? I noticed it happens in 1st at any throttle input, and even when not in gear it will almost "bounce" off 3500 like a redline. I can push past it with more throttle, however.

Things I'm planning to do in January:

Brakes
Try to free up the wastegate
Distributor cap
rotor
Ign. Coil
plugs
air filter
fuel filter
PCV
Shocks/Struts

Author:  fxyxixe [ Wed Jan 18, 2017 1:34 am ]
Post subject:  Re: 87 Sprint Turbo - Overboost or Fuel Cut in high RPM + CE

Final answer - stuck wastegate!

Fixed. Now the 3500 RPM hesitation is the next stop.

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