89 350 tbi problems

[Vbb199]

I've got an Edelbrock E-Street TBI and it needs 59-68psi minimum.

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That's about what the holley efi I have needs for my 502

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[Vbb199]

So i found part of problem!...

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[Vbb199]

Screen is rotted away.. Thankfully the pieces of it I was able to get out of the pan in the tank! The tank is also not rusted out thankfully... But I have to run to the auto parts store and get another screen ...

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[Vbb199]

Truck runs like a champ now.. Fuel pump was once again the culprit.

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[Chevyguy]

Truck runs like a champ now.. Fuel pump was once again the culprit.

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It's awful hard on our older Chevy's to let them sit undriven. I had to deal with electrical issues when I let my 87 V20 sit undriven for a couple years. A year ago I replaced my drivers side fuel pump and sending unit. I used a Spectre Sending Unit, and a Delphi Fuel Pump.

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[Vbb199]

So we're back go this, last night I took apart the tbi unit, cleaned it out, all the vacuum outlets on it were blocked up and clogged.
It's 100% clear and clean with all new gaskets all around.
I replaced the IAC valve because I suspected it to be faulty seeing as the truck suddenly developed a high idle.
When I pulled out the iac, I noticed it was getting stuck, so I replaced it with a new one.

With the freshly overhauled TBI unit, I Fire the truck up now, it runs at about 1500 rpms (no tach), and when I put it in gear, it's stumbling.

Engine has only 20k on it, it's a almost brand new crate motor.

Does anyone have suggestions?

I can hear a wild vacuum/air leak where the IAC plunger advances forward.

Wondering if I should give it a moment to learn the new IAC's position?



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[Vbb199]

Might I add it stumbles badly in gear

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[bucket]

Sounds like it could be a vacuum leak.

A faulty (new) IAC valve is certainly not unheard of, but if it was causing the high idle, it would idle high in gear too.

 

[Vbb199]

Sounds like it could be a vacuum leak.

A faulty (new) IAC valve is certainly not unheard of, but if it was causing the high idle, it would idle high in gear too.

Any merit to the reset procedure of the IAC?
tried it.
Reset the Ecm (unplugged battery)
Stuck my special key into the ALDL into the A and B jumpers to put it into diagnostic mode, the IAC plunger extended fully, I then unplugged it, turned the truck off, then plugged the IAC back up and removed the key from the A and B jumpers.

Resetting ECM now to see how it does.

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[Vbb199]

Truck won't even fire up now.

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[bucket]

But it will with a little throttle, right?

I normally 'reset' the IAC simply by turning the ignition on and off a few times. Roughly 5 seconds on and 5 seconds off.

 

[Vbb199]

But it will with a little throttle, right?

I normally 'reset' the IAC simply by turning the ignition on and off a few times. Roughly 5 seconds on and 5 seconds off.

If I keep giving it gas it will, it's like the IAC plunger is now just stuck all the way out

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[Vbb199]

I kinda screwed up, I took the IAC out of the tbi, and then Stuck my jumper key into the A and B jumpers, but when I turned the key, it extended the IAC so far it actually shot the plunger out... Pretty sure that's now garbage.
I'm gonna exchange it and NOT do that again.

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[bucket]

If I keep giving it gas it will, it's like the IAC plunger is now just stuck all the way out

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Your current symptoms have uncovered another issue. Even with the IAC fully closed, the base idle speed should be high enough to keep the engine running. It sounds like the idle stop screw needs turned in a little bit.

 

[Vbb199]

Your current symptoms have uncovered another issue. Even with the IAC fully closed, the base idle speed should be high enough to keep the engine running. It sounds like the idle stop screw needs turned in a little bit.

I read about the idle stop screw, where's that at?
Truck used to idle high before all this went down dad said.


Edit, I found the idle screw

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