I need some help

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RossW

New member
I'm trying to get my 88 AllTrac running. So far I've replaced the turbo, intake pipes, cap, rotor, plug wires, plugs, knock sensor, O2 sensor, alternator, starter, and TPS. It still doesn't want to idle. It fast idles at 2k for about 20 seconds and then drops to 600 RPM, stumbles, and dies. If I unplug the TPS it drops more slowly, but ultimately it still dies. I'm running real short on ideas and the river near my house is looking tempting...

Does anyone in CT have experiance in troubleshooting the Gen1 3SGTE or have things like a known good TPS, ECU, or AFM lying around (just about the only things I haven't tested or replaced) that I could borrow to see if it fixes the problem? Thanks guys.
 
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RIalltrac

Active member
Do you have the repair manuals? (BGB) I believe there is a procedure in there for diagnosing a bad afm. I remember seeing somewhere that you can test the resistance in the unit while moving the flapper door. Not sure which wires you have to tap into though. To me your problem sounds afm related, not sure if you can interchange the afm's between generations of the 3s either. sorry i couldnt be more help.
 
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RossW

New member
Yeah, that's what I've been thinking. Lol, this car has run 4 days and I've owned it for like 9 months.
 
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illGT4

New member
What are you referring to when you say:

"you can hear the exhaust leaks."

what exhuast leaks?

what are you pulling for vacuum at 2k and at 600 rpm?
 
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illGT4

New member
here is my 2 psi...


your intial 2k is because of a leak.. this is sucking unmetered air.

your 600rpm deal is related.

you may have a stuck iac valve.

have you checked the throttle cable is functioning properly?
have you tried bringing the idle up?
 
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alltracman78

Active member
if it's sucking unmetered air, why would it idle high? That makes no sense. It should idle low all the time, or even have to have the throttle held open to idle.
 
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illGT4

New member
alltracman78":2m4obzbw said:
if it's sucking unmetered air, why would it idle high? That makes no sense. It should idle low all the time, or even have to have the throttle held open to idle.
Click to expand...


it's the same as having the throttle plate open.

when working on 4 runner the other day.. we started it with the cold start injector out , but connected to watch it's spray pattern. As soon as the motor is started, the gapping hole in the intake manifold is sucking in air after the AFM. (3ZV-E)

I understand your train of thought. This experience the other day has made me rethink things also.
 
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alltracman78

Active member
But why would it be the same? if the throttle plate is open, the vaccum from the engine will open the flapper in the afm. If you have a hole, it will bypass the afm, which will stay closed, unless you give it some hellacious vaccum. :D
 
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illGT4

New member
alltracman78":2i31um9j said:
But why would it be the same? if the throttle plate is open, the vaccum from the engine will open the flapper in the afm. If you have a hole, it will bypass the afm, which will stay closed, unless you give it some hellacious vaccum. :D
Click to expand...

I understand what you are saying.. should make it die.. this time it didn't.. odd.
 
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RossW

New member
Problem has been traced to flakey TPS and IAC, the car idles great now that that's been fixed. Now I just need a new mid-pipe so I can pass emissions (damn rotted flexpipe).
 
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illGT4

New member
Great to hear!

My poor cold idle has to do with the damn IAC valve also.

And I also need a midpipe, but only because I'm sick of the stock exhaust on this 165. lol.. need better exhaust so I can add this MBC i've got laying here.
 
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RIalltrac

Active member
okay I have to ask, but what is an IAC valve. I have just about all the abbreviations down, but I cant think of what this one is. My cool idle sucks lately, and I'd love to track down the culprit.
 
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RossW

New member
Idle Air Control Valve. It's the little bastard under the throttle body that's supposed to regulate air flow at idle.
 
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