help stumble 7mgte!!!

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ccguy

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Oct 26, 2011
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i need your help again. i fixed the tps wiring and the tps is working perfect (as you will see in the video it shows how much throttle is open in volts).
itis a bone stock 1987 7mgte motor.
there is a hesitation, stumble, hiccup at around 2500 rpm.
it is running very rich and getting horriable milage.
if it is a cold motor it runs good for about 40 seconds then this stumble starts.
i have an inline walbro and a intank OE supra pump.

while driving it can rev above the biccup but if the throttle is barely cracked it accels like i am flooring it. when the speed catches up to how much the throttle is open it acts like there is a dead spot. and the throttle is like a switch between on or off.

if i rev it up and hold it at like 4k and let it off it revs down and almost dies or dies.
most i have boosted on that crap gauge is 4psi.
io have great vacuum.

video HELP
http://www.youtube.com/watch?v=vOdnPqhucyw&feature=youtu.be
 
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ccguy

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Oct 26, 2011
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az
SC61 MK3;1891713 said:
Why do you have an inline walbro and in tank pump on a bone stock 7mgte?
Click to expand...
the walbro was the only one inline and nothing in the tank. so the walbro was up on the fender of the truck in the engine bay and i did not think it could lift the fuel it needed to fuel up when the rpms went up. so i fabbed up the intank one to act like a lift pump. it does not make a difference if they are both on or just the walbro. so i pulled the fuse to the one in the tank and it runs the same.
 
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ccguy

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Oct 26, 2011
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hvyman;1891716 said:
Did you bypass or drill out the j tube?
Click to expand...
the j tube is still on the block not drilled out but i bypassed it and it is going straight to the fuel return pipe to the tank.
 
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ccguy

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Oct 26, 2011
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just compression tested it.
#1-145
2-145
3-145
4-145
5-145
6-135
also i dont have the factory boost sending unit hooked up. the wiring showed that it went to the gauge only.
what rpm does the stock trim start to boost?
when does the fuel up vsv open? it does not matter if the fpr has vac or not.
 
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ccguy

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Oct 26, 2011
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yea stock fpr and it has the vac line going to the fuel up vsv
 
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JStoked

JStoked

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Jun 27, 2010
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Really??? Come on ugh so tired of these silly questions. For one a inline fuel pump is a NO NO!!And duh that is why there is a place to put for a vaccum line on the fpr. Things you guys ask questions about. SEARCH!!!! It's called GOOGLE. And read. We are here to help don't get me wrong at all. Read dealing with the old school guys. It's a sticky. Then ask your questions.
 
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ccguy

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Oct 26, 2011
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az
JStoked;1892074 said:
Really??? Come on ugh so tired of these silly questions. For one a inline fuel pump is a NO NO!!And duh that is why there is a place to put for a vaccum line on the fpr. Things you guys ask questions about. SEARCH!!!! It's called GOOGLE. And read. We are here to help don't get me wrong at all. Read dealing with the old school guys. It's a sticky. Then ask your questions.
Click to expand...

ok there smarty, no joke the fpr is sopose to have a vac line on there. I WAS ASKING what RPM the fuel up vsv activates to bump the fuel pressure up. so obviously you dont know....
this is not a straight supra, is is only the motor and it has been swapped into a 1980 truck. i have been searching for the last 8 months EVERY night on this problem as well as trying everything. this is a little more advanced than putting a used front mount inter-cooler on.....
 
jetjock

jetjock

creepy-ass cracka
Jul 11, 2005
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Redacted per Title 18 USC Section 798
Operation of the FPU vsv is covered in the service manual. In a nutshell it operates only when the coolant is hot and then only for appx 2 minutes max after starting. It raises fuel pressure by *disconnecting* vacuum to the FPR and venting it to atmospheric pressure. Not that this has anything to do with your problem.
 
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ccguy

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Oct 26, 2011
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az
thank you for the info. i swear i have almost read every page in the fsm and other factory bulletins but never got that.
do you all think it sounds like a boost leak? i do but i cant find it? would this be the symptoms of a bad turbo? wastegate?
 
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ccguy

New Member
Oct 26, 2011
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az
yea, i have boost leak tested it 3 times with low psi compressed air. and i have smoke tested it as well then added some psi.
i will try to post up another video soon. i need to put it back together to start it.
i was able to pick up a analog boost gauge so i can see what it is doing better than that digital gauge
 
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ccguy

New Member
Oct 26, 2011
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az
when i get it back together i will re check the timing. i have grounded the engine a couple of places but i am going to add a few more
 
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ccguy

New Member
Oct 26, 2011
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az
the fuel pump is running and wired correctly.
i found some real wiring diagrams specifically for the 87 7mgte. so i need to check my wiring and see where i missed something.
http://www.turboninjas.com/mk3supra/
feeling good about it now.
thx for the encouragement. i will let you all know what i find. thx
 
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ccguy

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Oct 26, 2011
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az
i have a feeling it is in the HAC.
when i have it connected, the tps at the ecu it is 2.8 k ohms.
when it is unplugged it is 4.8k ohms.
with it plugged in it runs worse and with it unplugged it runs like in the video. so?????????

there is 4.8 volts from the ecu going to the hac with the ign key on. as well to the tps and afm.
does anyone else know what their vta k ohms is with the hac connected?
 
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