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606 Posts
Discussion Starter #1
-car wont boost,
-idles very well, runs good until it starts to build boost, then stutters very badly. Like if I was in an intersection and a car was coming, I'd be able to do nothing but watch it run into me cause I cant accelerate or it will stutter like hell. But in such a poor state, i was able to get up to 70mph on the highway, just had to go easy on the throttle, pushing it no more than 2k rpm, not letting it try to build boost. Its NOT the turbo, we did a leak down test and there is no leak (oddly enough), its NOT the alternator, we adjusted the cps and that had no affect. Although they are out of ideas, the local supra guys suspect the AFM so we'll be swapping electronics tomorrow to check that out. Any ideas??????!?!???? If its not the AFM, i think we'll be shit out of ideas. All i can think of is a bad ground, will check that. Remember, car runs fine until it starts to build boost.
 

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DO WORK!!
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2,275 Posts
Knock sensors could be bad or the KS wires, and that would throw your ECU into limp mode. you could also be running Very very lean. a WB02 would tell you this.
 

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SupraStore.com
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2,134 Posts
Holy crap thats exactly why my Supra isnt running right now..I have a MAF-T though, so maybe my wiring for it is shoddy?

Bah, going to flat out replace the pump and knock sensors
 

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Boostin
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1,280 Posts
to much factors now.

could be....
- afm?
- fuel pump? ( might be a good time for a 255 walbro since it a only 69 ship on ebay) ;)


We forgot to see if the CEL came on when it studder. Maybe we should check that out.
 

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sounds like the afm to me. mine did the same thing. idled fine and then when you got to about 2k rpm it ran like complete shit and woiuldnt boost and would sputter forever and have no acceleration at all.
 

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Turbonetics..faggot asses
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1,062 Posts
I'm betting fuel pressure regulator
 

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Your ignorance...
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Interesting, my GF's car is doing the same thing, haven't had time to look into it but maybe I'll try swapping out the AFM from mine and see how it does.
 

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fuel filter? can you hear your pump at all, you might be overworking your pump with a clogged filter that cant deliver the fuel required to boost. any codes?
 

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LEADED FUEL ONLY
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It's overly rich is my bet. Or overly lean. Mod list??

When you adjusted the TPS, did you know what you were doing? Or did you just move it and drive, move it and drive, move it and drive???
 

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This Is Why I'm Hot.....
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1,984 Posts
aljordan said:
It's overly rich is my bet. Or overly lean. Mod list??

When you adjusted the TPS, did you know what you were doing? Or did you just move it and drive, move it and drive, move it and drive???
Hello Alan,
Good point.

Another note regarding the AFM- my car ran poorly for a 2-3 month stretch while I diagnosed a variety of possibilities. When I had concluded checking everything & came up empty-handed...I asked a friend to swap AFMs & vrooooom, it ran like gangbusters again. Mind you, there were no ECU codes of any kind, none.

Take care.
 

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Boostin
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1,280 Posts
aljordan said:
It's overly rich is my bet. Or overly lean. Mod list??

When you adjusted the TPS, did you know what you were doing? Or did you just move it and drive, move it and drive, move it and drive???

yea we were advacing it and retarding it. all still sudder at high rpm. can't seem to pass 4k.
 

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LEADED FUEL ONLY
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^^^^

There's your problem.

Adjust it correctly and i bet it solves your problem. make sure you put 2 screws to hold the TPS rather than just one. I've had the TPS with one screw come out of adjustment.

http://www.cygnusx1.net/supra/library/TSRM/fi/FI_103.html

Also.. don't just advane or retard the timing without the proper way to set it. Do it correctly per toyota specs.
 

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Now with less BHG...
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409 Posts
I'm still banking on AFM. I drove w/ a bad TPS for ~3 weeks, and it ran ok, just idles high as hell.

And ya, messing with timing without a light is a big no-no...
 

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Hardtop FTW
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1,784 Posts
Sounds exactly like what happens whens the AFM is unplugged. Check your connections/swap the AFM with a known good. You'll fix it.
 

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reedjsupra said:
I'm still banking on AFM. I drove w/ a bad TPS for ~3 weeks, and it ran ok, just idles high as hell.
Same here, when I bought my car the damn TPS was unplugged altogether. Non working TPS just gives you high idle, run rich, and crappy throttle responce. Otherwise you'd never know the difference
 

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LEADED FUEL ONLY
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2,068 Posts
wellllll.. lemme break it down for you guys...

TPS is a throttle enrichment device. When it sees throttle change it adds or subtracts fuel accordingly.

The guy is having problems on large throttle increases, such as getting into boost. Doing that takes some decent throttle input. he doesn't have problems when he is gentle with the throttle and keeps load to a minimum. This is where a TPS wouldn't be as crucial.

At the very least check it and ensure it's adjusted correctly.
 

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All you guys are freshly tuned up, right?? (noone said this yet?)
-plugs, wires, FF, ect...
 
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