Mk3 Supra Boost Problems
08-06-2003, 07:38 PM
#1
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Join Date: Mar 2003
Location: Tampa
Posts: 582
Well, this post is acctually for a friend, he's got an 88 supra turbo, real nice car, just wont boost for crap.
A couple months back we disabled the WG accuator rod, because the car was bogging real bad under WOT... it was just terrible, so we figured it was due partly to having bad gaskets, and having a bad valve cover gasket. SO we replaced all those, no problems. Today we installed a boost guage, pretty simple and strait forward, the car is reading -20 vac, at idle.... when you rev with no load the guage goes to 0, perfect..
So we go, reinstall the WG rod, figure everything is going to work properly... it's a no go
She wont boost, or even rev past 2500-3000 rpms under WOT. What in the hell could be causeing this lack of boost? thanks again guys
-markus
"If you need more info, just ask. Again it's a buddy's car, because supraforums.com is DEAD"
A couple months back we disabled the WG accuator rod, because the car was bogging real bad under WOT... it was just terrible, so we figured it was due partly to having bad gaskets, and having a bad valve cover gasket. SO we replaced all those, no problems. Today we installed a boost guage, pretty simple and strait forward, the car is reading -20 vac, at idle.... when you rev with no load the guage goes to 0, perfect..
So we go, reinstall the WG rod, figure everything is going to work properly... it's a no go
She wont boost, or even rev past 2500-3000 rpms under WOT. What in the hell could be causeing this lack of boost? thanks again guys
-markus
"If you need more info, just ask. Again it's a buddy's car, because supraforums.com is DEAD"
08-06-2003, 08:46 PM
#3
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Join Date: Mar 2003
Location: Tampa
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The turbine itself is fine, spins freely and has very little-no free play
The wastegate is strange, i removed it and useing my hands pulled and pushed. I could only pull it out... pull it out, retracts on it's own... pull it out retracts on it's own. It's very very strange. With the wastegate not being hooked up, the car runs and drives just fine (just doesnt have any boost)... when we connect the WG rod it will get up to about 2500 rpms and just about when we FEEL the boost coming on the motor bogs real bad, almost like it's hitting fuel cut, the Check Engine light comes on, i let off the gas, everything goes back to normal, just can't rev over 2500-3000 rpms in gear. Sitting in the driveway with no load, boost guage shows -20 Vac at idle. Revs freely to redline with NO LOAD. Strange thing is we can't hear her blow off when we rev with no load.
-Markus
"Any help would be GREAT!"
p.s. 1988 mk3 turbo supra
The wastegate is strange, i removed it and useing my hands pulled and pushed. I could only pull it out... pull it out, retracts on it's own... pull it out retracts on it's own. It's very very strange. With the wastegate not being hooked up, the car runs and drives just fine (just doesnt have any boost)... when we connect the WG rod it will get up to about 2500 rpms and just about when we FEEL the boost coming on the motor bogs real bad, almost like it's hitting fuel cut, the Check Engine light comes on, i let off the gas, everything goes back to normal, just can't rev over 2500-3000 rpms in gear. Sitting in the driveway with no load, boost guage shows -20 Vac at idle. Revs freely to redline with NO LOAD. Strange thing is we can't hear her blow off when we rev with no load.
-Markus
"Any help would be GREAT!"
p.s. 1988 mk3 turbo supra
08-07-2003, 09:48 PM
#5
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Join Date: Sep 2002
Posts: 282
check the engine light! Find out what the code is that's coming on.
The wastegate should retract on its own, that's the spring. Boost pushes it open, the spring closes it. That's what spring pressure means, it's the amount of boost needed to overcome the spring.
The wastegate should retract on its own, that's the spring. Boost pushes it open, the spring closes it. That's what spring pressure means, it's the amount of boost needed to overcome the spring.
08-08-2003, 01:36 AM
#6
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Join Date: Aug 2003
Posts: 2
It has to be electrical it is probably the standard boost cut out or computer is faulty
get that checked out , it doesn't sound at all like its mechanical.
when it hits 3 grand does the car jolt forward hard as if it wants to go on Boost but wont ???
get that checked out , it doesn't sound at all like its mechanical.
when it hits 3 grand does the car jolt forward hard as if it wants to go on Boost but wont ???
08-08-2003, 12:33 PM
#7
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It feels very strange, if you start off in first, and WOT 2500 rpms boost starts to come on.. than right at 3000 rpms the boost just DIES! and the car bucks and lurks like a horse... check engine light comes on for an instant, than all is normal again.. Shift into second go WOT.. same thing happens. The car will not rev over 3000 rpms...
Now, when driving it easy... like NOT driving full throttle it WILL accell over 3000.. but say you get it to around 5000 rpms slowly, than WOT it it bog, cuts out, light comes on and it starts all over again.
-markus
"I'm not sure WTF is wrong with it."
Now, when driving it easy... like NOT driving full throttle it WILL accell over 3000.. but say you get it to around 5000 rpms slowly, than WOT it it bog, cuts out, light comes on and it starts all over again.
-markus
"I'm not sure WTF is wrong with it."
08-28-2003, 11:36 PM
#9
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Join Date: Aug 2003
Posts: 1
Dunno if this still applies now that SF is back up, but his AFM is probably dirty. My guess is it's all oily from the PCV system, Pull out the AFM and check. Especially the electronics, the black box screwed into the metal housing with 3 screws. Carefully undo the screws and remove the electronics, it's got a plastic wedge-shaped piece that extends down into the chamber. If it's dirty, clean out the housing (sans electronics) with carb cleaner, and carefully wipe off the plastic of the electronics unit with a rag. Be careful not to bend any of the honeycomb material on the front of the housing, and definitely don't get any carb cleaner on the electronics section. The Karmann-Vortex AFM uses mirrors to detect the vortexes made by the air as it passes past the plastic wedge (the honeycomb straightens the air). The mirrors are very fragile and solvents like carb cleaner will ruin it. Anyway, get everything nice and clean and put it all back together (don't forget to reconnect the AFM connector, it's easy to forget) and I'll bet you your fuel cut issue is solved. HTH.
Dan
Dan
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