1987 Chevrolet 350 tbi high idle

iamtherealJayy

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Springs were from dad being a little slow when swapping the tbi stuff onto a carb block when he blew the engine, no doubt in my mind. I’m going to go video the throttle cable a startup, idle, and blip of throttle.
 

iamtherealJayy

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During my video I did several blips of the throttle, a start after sitting four or five days(no it doesn’t start any faster even if I’d drove it yesterday if I’ve already drove it today it might have started faster) and two revs to above 2500. When watching the footage the in the engine bay clip doesn’t sound as obvious over the engine chattering. But maybe from the speed of the chattering to can tell it’s staying around 1500 rpms for way longer than it should.
 

iamtherealJayy

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iamtherealJayy

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I’d put a new tps on the truck with no change so I removed it to keep the GM part on the engine. The vacuum line to the Map is good the map is new along with egr and engine coolant temp sensor in the intake manifold(the map or ects is what made the truck finally idle on regular 87 fuel, when I first got it the truck wouldn’t idle on anything but premium 93.)
 

AuroraGirl

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400(?), 350
I’d put a new tps on the truck with no change so I removed it to keep the GM part on the engine. The vacuum line to the Map is good the map is new along with egr and engine coolant temp sensor in the intake manifold(the map or ects is what made the truck finally idle on regular 87 fuel, when I first got it the truck wouldn’t idle on anything but premium 93.)
the TPS on a square with early TBI im pretty sure has an adjustment procedure. electrical. You should have a quality new one, the original is physically more worn out. infact, we may be looking at a calibration issue
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iamtherealJayy

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350, 350, 454
I have a multimeter I just couldn’t figure out how to check the reading from it. I also could not get the Aldo cable to work if you recall. If you’ve got an article to show me about how to check it with a multimeter I’ll go do that
 

AuroraGirl

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iamtherealJayy

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So use multimeter to check blue wires voltage? Sound correct?
 

iamtherealJayy

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Reading .35 at around 650 rpm
 

iamtherealJayy

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AuroraGirl

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So use multimeter to check blue wires voltage? Sound correct?
has to be plugged in to the sensor and you you need to know what the sig return voltage is im pretty sure, reference should be constant
found your issue, while you play with throttle see if it returns to there everytime
 

gmbellew

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You can check TPS key on, not running. 0.36 is a little low. I think values around 0.5 are the typical low end. Mine is actually around 0.8 at rest, and that is working fine. I think the ECM uses the at rest reading as "idle" every time you start it. There is a good description of this in the drivability manual.
 

iamtherealJayy

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Engine Size
350, 350, 454
Thanks for mentioning it doesn’t have to be running lol, in the morning I will get closed throttle to wide open and back to closed amounts
 

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