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Discussion Starter · #1 ·
This is the second TBI engine I have ran across that would not idle, as soon as you let off the gas pedal it dies.

What causes this? bad fuel pump, IAC, clogged lines?

The first one I swapped the distributor and intake and just ran a holley but I dont want to do that this time
 

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Could be lots of things, check the codes first....Might not have anything to do with the TBI, check for vacuum leaks too.
 

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Check vacuum lines, IAC and be sure you have good clean grounds.
 

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Sounds like MAP or TPS.
Check the voltage at each pin of those 2 sensors with the key on and when running.
You will need a paper clip or pin to touch the connection from outside the connector.
The pin can be used to puncture the insulation to touch the wire.

When testing the TPS, open the trottle while watching the meter and see if it goes up and down smooth.

Have you checked the fuel pressure?
When was the last time you changed the filter?

and perform the initial setup procedures so you know the IAC and TPS are set right.
 

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you may try to do an idle relearn to pcm , i assume engine is running normally during normal driving ? , if it only dies at low engine speed this may help . 1 . turn ignition switch to on for 10 seconds , do not start 2. turn ignition switch off for ten seconds 3 . start engine and verify proper engine speed ( should be about 450-475 for automatic trans slightly higher for manual ) i hope this helps you .
 

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you may try to do an idle relearn to pcm , i assume engine is running normally during normal driving ? , if it only dies at low engine speed this may help . 1 . turn ignition switch to on for 10 seconds , do not start 2. turn ignition switch off for ten seconds 3 . start engine and verify proper engine speed ( should be about 450-475 for automatic trans slightly higher for manual ) i hope this helps you .
I don't think that applies to an 89 TBI. They have an ECM not PCM.
The IAC reset is part of the initial setup procedures but you have to connect pin A/B of the aldl then it drives the IAC closed. This sets the 0 reference. then when you open it the IAC goes to 145 for park position. The system also resets itself at shut down when it drives the IAC closed and then to 145. If you watch it on winaldl you can see the IAC drive after you turn the key off.


egr valve stuck open a little and they wont idle, and it wont throw a check engine light either
Good point
 

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I had one in the shop the other day and it was the pickup coil in the distributor.It would die every time the truck went to idle,but ran fine other than that.
 

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Discussion Starter · #11 ·
As long as you give it some throttle it runs good. I'll check all of this saturday, good idea on the pickup coil in the distributor

Keep the ideas coming, I had checked all of this on the other truck I had that was doing the same exact thing and I never could fix the problem
 
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