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stalling, erratic idle 5.0 TBI

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Old Aug 30, 2016 | 06:22 PM
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stalling, erratic idle 5.0 TBI

As the subject states, stalling, erratic idle.

Acts as if it is flooded....will only start with throttle wide open (foot to the floor), and even then, sputters for a few seconds (burning off excess fuel in the cylinders?) before it will run right...

I am thinking a TB rebuild and new injectors are in order--thoughts? Could it be something else?
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Old Aug 30, 2016 | 06:23 PM
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Re: stalling, erratic idle 5.0 TBI

sorry--92 RS
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Old Aug 30, 2016 | 07:45 PM
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From: Milwaukee
Car: 92 Firebird, 77 Trans Am SE, 86 Z28
Engine: 5.7 HSR, T/A 6.6, empty
Transmission: T-5, TH350, T-5
Axle/Gears: 3.08 posi, 3.23 posi, 3.23
Re: stalling, erratic idle 5.0 TBI

Sounds like an injector is sticking open maybe.......ohm them out to test them to start. Maybe a bad CTS?
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Old Aug 30, 2016 | 07:52 PM
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Re: stalling, erratic idle 5.0 TBI

CTS?

How do I "ohm them out?"
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Old Aug 30, 2016 | 07:57 PM
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From: Milwaukee
Car: 92 Firebird, 77 Trans Am SE, 86 Z28
Engine: 5.7 HSR, T/A 6.6, empty
Transmission: T-5, TH350, T-5
Axle/Gears: 3.08 posi, 3.23 posi, 3.23
Re: stalling, erratic idle 5.0 TBI

coolant temperature sensor.


Take an ohm meter......touch one probe to one injector terminal.....touch the other terminal to the other probe.....read what the ohms are..16.0 is typical....I think..may be different with tbi injectors. Search and you'll find a ton of info on them.
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Old Aug 30, 2016 | 08:06 PM
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Re: stalling, erratic idle 5.0 TBI

Thanks--Coolant temperature sensor would cause earrtic idle, and symptoms above? Why is that?

Sorry, new to ECM vehicles...I'm used to old school carbureted!
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Old Aug 30, 2016 | 08:10 PM
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From: Milwaukee
Car: 92 Firebird, 77 Trans Am SE, 86 Z28
Engine: 5.7 HSR, T/A 6.6, empty
Transmission: T-5, TH350, T-5
Axle/Gears: 3.08 posi, 3.23 posi, 3.23
Re: stalling, erratic idle 5.0 TBI

The cts may think it's colder than it is....causing the ecm to dump in fuel it doesn't need. Or that it's lean and isn't getting enough fuel.
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Old Aug 30, 2016 | 08:13 PM
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aliceempire's Avatar
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From: Milwaukee
Car: 92 Firebird, 77 Trans Am SE, 86 Z28
Engine: 5.7 HSR, T/A 6.6, empty
Transmission: T-5, TH350, T-5
Axle/Gears: 3.08 posi, 3.23 posi, 3.23
Re: stalling, erratic idle 5.0 TBI

The cts ohms the same as injectors. You compare the ohms to the actual air/engine temperature on a graph like this post #2 https://www.thirdgen.org/forums/tbi/...cold-help.html
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Old Aug 30, 2016 | 08:14 PM
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Re: stalling, erratic idle 5.0 TBI

Makes sense, except, even from cold start, I have the issue with having to open the throttle all the way to start...

I'm likely going to order the parts to rebuild the throttle body and I'll replace the injectors while I'm at it. Car has been running fine since I bought it in early June (only had it out a handful of times, though). Guy I bought it from got it form someone that said it had been sitting for at least 5 years...Proabbly need to be gone through anyway (fuel system, that it)...

Just wanted to make sure I was on the right track...
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Old Aug 30, 2016 | 08:26 PM
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From: Milwaukee
Car: 92 Firebird, 77 Trans Am SE, 86 Z28
Engine: 5.7 HSR, T/A 6.6, empty
Transmission: T-5, TH350, T-5
Axle/Gears: 3.08 posi, 3.23 posi, 3.23
Re: stalling, erratic idle 5.0 TBI

Luckily, the tbi is super simple and common. Good luck!
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Old Sep 2, 2016 | 06:44 PM
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Re: stalling, erratic idle 5.0 TBI

hanks for the help...swapped out the CTS (didn't touch the TB or the injectors...

Car is running the best since I bought it a couple months ago.

The difference really is amazing--night and day! I never would have thought of a coolant sensor causing driveability issues

Thanks for the help.
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Old Sep 2, 2016 | 07:58 PM
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From: Milwaukee
Car: 92 Firebird, 77 Trans Am SE, 86 Z28
Engine: 5.7 HSR, T/A 6.6, empty
Transmission: T-5, TH350, T-5
Axle/Gears: 3.08 posi, 3.23 posi, 3.23
Your welcome. Glad you figured out the problem. They're more common of an issue then most people think.
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